Preliminary biology - KISS Notes Patterns in Nature. Do not own....
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Preliminary Biology Topic 2
PATTERNS in NATURE What is this topic about? To keep it as simple as possible, (K.I.S.S.) this topic involves the study of: 1. LIVING CELLS & THEIR STRUCTURE 2. CHEMICALS MOVE IN & OUT THROUGH MEMBRANES 3. NUTRITION IN PLANTS & ANIMALS 4. GAS EXCHANGE & INTERNAL TRANSPORT 5. CELL DIVISION FOR GROWTH & REPAIR
but first, an introduction... Organization of a Multicellular Organism
Cells All living things are composed of microscopic “lumps” called cells.
A building is not just a pile of bricks, and an army is not just a rabble of soldiers. Each has a structure, and levels of organization so everything works together.
Some organisms are composed of just a single cell. All familiar organisms are made of many cells; for example, your body is composed of approximately 300 billion cells... you are “multicellular”.
Similarly, your body is not just a big heap of cells. It has levels of organization... a
Each cell is a tiny sac of “protoplasm”... water with a complex mixture of chemicals dissolved in it, plus many structures called “organelles” (little organs).
CELL is the basic unit of any living thing. A number of similar cells working together is a...
TISSUE. (e.g. muscle tissue, bone tissue.)
GENERALIZED DIAGRAM OF A LIVING CELL
Various tissues are combined to make an...
Organelles
ORGAN. (e.g. heart, kidney, liver.) A number of organs work together for a specific purpose. This forms a...
SYSTEM.
(e.g. digestive system.)
Finally, all the body systems working together form... YOU - a functioning, multicellular organism.
“Membrane” on the outside contains the cell , and controls what goes in or out
Cytoplasm is a jelly-llike liquid which fills the cell
Cell
& Chemistry
Plants and animals have cells with a few important differences. Organisms such as fungi are different again, while bacteria have a totally different cell structure. Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
In this topic you will study the basics of the structure and functioning of living things. structure
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Vital Body Systems
Cell Division
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CONCEPT DIAGRAM (“Mind Map”) OF TOPIC Some students find that memorising the OUTLINE of a topic helps them learn and remember the concepts and important facts. As you proceed through the topic, come back to this page regularly to see how each bit fits the whole. At the end of the notes you will find a blank version of this “Mind Map” to practise on.
Cell Chemicals
Cell Organelles Cell Theory
Structure of Membranes
Plant & Animal Cells
Living Cells & Their Structure
Diffusion & Osmosis Surface Area to Volume Ratio
Chemicals Move In & Out Through Membranes
Photosynthesis & Respiration
Nutrition in Plants & Animals
PATTERNS in NATURE
Structure & Function of Leaf
Digestion in Animals
Gas Exchange & Internal Transport
Cell Division for Growth & Repair
Reasons for Cell Division
Gas Exchange in Animals
Mitosis
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Gas Exchange & Transport in Plants
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Circulation in Animals
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1. LIVING CELLS & THEIR STRUCTURE The Cell Theory
History of Our Knowledge of Cells
The “Cell Theory” is one of the fundamental concepts in Biology. It simply states:
Robert Hooke, 1665 Hooke is credited with being the first person to see cells and name them. Using a Sketch of primitive Hooke’s microscope, he microscope looked at a piece of cork (dead tree bark) and saw tiny “boxes” like the rooms and compartments of a gaol or monastery. (hence “cells”)
• All living organisms are composed of cells or are the product of cells. (e.g. viruses) • All cells are produced from pre-existing cells. The evidence supporting the Cell Theory has come almost entirely from the use of microscopes to examine living things. Our knowledge of cell structure and function has developed as the technology of microscopes advanced over the last 300 years or so. Initially, only light microscopes were available, but since the 1930’s electron microscopes have revealed more detail of cell structure and function.
Comparison: Light & Electron ‘Scopes Light Microscope
Electron Microscope
How the image is formed
beam of light focused by glass lenses
beam of electrons focused by magnetic fields
Magnification
generally about up to 1,000,000 X 500 X. (500 times more Maximum powerful) about 2,000 X
Resolution (ability to see fine details)
about 0.2 μm
μm) micrometres (μ
Anton van Leeuwenhoek, 1676 van Leeuwenhoek used a very simple microscope, but it was equipped with an excellent lens, through which he saw living micro-organisms swimming around in a drop of water. Over the next 150 years, microscopes improved, and it was suspected that cells were present in all living things. Robert Brown, 1827 Brown was the first to discover structures inside cells. He discovered and described the nucleus inside plant cells.
about 0.0002 μm (1,000 times better detail)
By about 1840, the “Cell Theory” was becoming accepted by most biologists, because cells were observed in every organism studied. Louis Pasteur’s discoveries showed that infectious diseases were caused by “germs”, which were microscopic, cellular organisms.
1 μm = 0.000001(10-6)metre.
1 micrometre is 1/1000 of a millimetre
How Big Are Cells Anyway? Typical Plant Cell 50-100 μm
Rudolf Virchow, 1859 and Walther Flemming, 1879 Between them, these two German scientists clarified the process of cell division, by which cells produce more cells. This established the principle that all cells come from pre-existing cells.
Typical Animal Cell 5 - 20 μm Bacterial Cells 1 - 5 μm
In the 20th century, the electron microscope opened up our knowledge of the fine detail of cell structures and their functions.
SCALE: 100 μm (0.1 mm)
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Cell Organelles Visible with a Light Microscope You may have done practical work in class to use a light microscope to view cells in living things.
Generalized ANIMAL CELL
Generalized PLANT CELL
NUCLEUS
Small Vacuoles (if any at all)
CELL WALL (outside of membrane)
Large VACUOLE CYTOPLASM
There are probably no actual cells which looks just like these. Real shapes vary greatly.
CELL MEMBRANE
CHLOROPLASTS (green colour)
The Major Differences Between Plant & Animal Cells Plant cells have a tough CELL WALL on the outside of their cell membrane. Many plant cells contain a large VACUOLE. Animal cells rarely have vacuoles, and if present they are small. Many plant cells contain CHLOROPLASTS. These are green in colour because they contain the pigment chlorophyll. Chloroplasts are the sites of PHOTOSYNTHESIS, where plants make food. Note: not all plant cells have chloroplasts... for example, cells in the underground roots cannot photosynthesise, so do not contain any chloroplasts.
What the Electron Microscope Reveals The superior magnifying power and resolution of the electron microscope has given us a much more detailed knowledge of the cell and its organelles. The diagram below is a sketch of a plant cell similar to the one above, but with the added details that the electron microscope has revealed. The extra organelles shown are generally NOT visible with a light microscope. Golgi apparatus
Cell Wall Cell Membrane
Endoplasmic Reticulum A network of membrane structures connected to nucleus & extending throughout the cytoplasm
Vacuole
Nucleus Extra detail revealed
The tiny Ribosomes are often attached to the E.R.
Chloroplast internal structure
Mitochondrion. Site of cellular respiration
Stacks of flat membranes (grana) contain the chlorophyll
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The Organelles... Structure & Function The Nucleus
NUCLEUS
This is the control centre of the cell. Inside the nucleus are the chromosomes containing DNA, the genetic material. There is often a nucleolus present. This is the site for production of RNA, a “messenger” chemical which leaves the nucleus carrying instructions to other organelles. The nuclear membrane has holes or “pores” to allow RNA to exit.
Nucleolus RNA manufacture
Nuclear membrane with pores, for RNA exit
Nuclear material “chromatin”. (Chromosomes unwound and spread out)
The Cell Membrane Mitochondria
This is not only the boundary of the cell, but also controls what goes in or out of the cell. This is studied in more detail in the next section.
(singular: mitochondrion)
This is where cellular respiration occurs Glucose + Oxygen (sugar)
Endoplasmic Reticulum (E.R.)
Carbon + Water + ATP Dioxide
E.R. is a network of membranes which form channels and compartments throughout the cytoplasm of the cell. Its function can be compared to the internal walls of an office building which divide the building into “rooms” where different operations can be kept separate so that each does not interfere with others.
The ATP produced by respiration carries chemical energy all over the cell to power all the processes of life. The mitochondria are therefore, the “power stations” of the cell, converting the energy of food into the readily usable form of ATP.
ENDOPLASMIC RETICULUM
MITOCHONDRION Outer membrane
Inner membrane folded into “cristae” with respiration enzymes attached
Membranes enclose channels and “rooms”
RIBOSOMES attached to membranes
The E.R. structure provides channels for chemicals and “messengers” to travel accurately to the correct locations, and for chemical production to occur in isolation from other operations.
Inside a mitochondrion is a folded membrane with many projections (“cristae”). This structure provides a greater surface area, where the enzymes (control chemicals) for respiration are attached in correct sequence for the steps of the process.
This structure helps cells function Often found attached to the E.R. are the tiny Ribosomes. These are the sites of production of proteins, the main structural and functional chemicals of living cells. RNA “messengers” from the nucleus attach to a ribosome to make the specific proteins that the cell needs.
This structure helps the organelle do its job more efficiently. Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
Membranes
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Chloroplasts The Golgi Apparatus is a semi-circular arrangement of membranes which are concerned with packaging chemicals into small membrane sacs (“vesicles”) for storage or secretion. Curved GOLGI BODY
Chloroplasts are found only in photosynthetic plant cells. The electron microscope has revealed that the chloroplast is not just a bag of chlorophyll, but has an organized internal structure which makes its functioning more efficient. CHLOROPLAST
membrane sacs
“Stroma” zone
Vesicles pinch-o off for storage or secretion
Membrane stacks (“grana”) containing chlorophyll
Lysosomes form this way
One type of “vesicle” produced by a Golgi Body is the Lysosome. These membrane sacs contain digestive enzymes which can destroy any foreign proteins which enter the cell.
Double membrane envelope
The “grana” are stacked membrane sacs containing chlorophyll, which absorbs the light energy for photosynthesis. This lightcapturing step is kept separate from the “stroma” zone, where the chemical reactions to make food are completed.
Lysosome enzymes also rapidly digest the contents of a cell which has died, so that your body can clean up the remains and replace the dead cell.
The Importance of Membranes Except for the tiny ribosomes, all the cell organelles are built from, and surrounded by, membranes. The membranes provide:• the infrastructure of the cell. • channels for chemicals to move through. • packaging for chemicals which need to be stored. • points of attachment for chemicals (“enzymes”). • control over what moves in or out of each organelle, and in or out of the entire cell. The “membrane-bound” organelles help the cell’s various functions to be carried out with greater efficiency. Having these membrane-based organelles is the defining characteristic of the “Eucaryotic” group of organisms, which includes all plants and animals. Bacterial cells do NOT have all the membrane-type organelles, and can only operate efficiently by being very small. Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
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List 5 additional organelles normally only visible with an electron microscope. (p)........................................ q)......................................... r).......................................... s).......................................... (t).........................................
Worksheet 1 Cell Theory & Cell Structure Fill in the blank spaces and diagram labels. The “Cell Theory” states that (a)................................ are composed of cells, and that all cells are produced from (b)......................................................
Complete these lists to describe the functions of the organelles. Function Organelle Cell membrane (u)
Our knowledge of cells is due mainly to the technology of (c).............................................. The (d)....................................... of a microscope refers to its ability to distinguish fine details. The (e)................................. ‘scope is far superior in both (d) and (f)...................................
(v)
Partitions cell into channels & compartments
Golgi apparatus
(w)
The man credited with being the first to see cells was (g).....................................................
(x)
Cellular respiration.
(y)
Photosynthesis
Cell wall
(z)
Label the parts of this plant cell seen with a simple light microscope. (h)................................. (i).................................
(m).........................
(j).................................
(k).................................
Which TWO parts of this plant cell would definitely never be seen in an animal cell?
(inside (k)
WHEN COMPLETED, WORKSHEETS BECOME SECTION SUMMARIES
(n)........................................ and
Practice Questions for this section are included in Worksheet 3
(o)..................................
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(l).................................
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2. CHEMICALS MOVE IN & OUT THROUGH MEMBRANES
The Chemicals That Cells Are Made From
INORGANIC CHEMICALS These include small simple molecules like water (H2O) and carbon dioxide (CO2), as well as mineral ions such as calcium, nitrate, phosphate, chloride, etc. Although these are often considered of lesser importance, you should remember that all living things are 75%- 95% water.
ORGANIC CHEMICALS “Organic” chemicals are based on the element carbon, which can form chains, rings and networks and so build the very complex molecules needed to make a living cell. Many are “polymers” made by joining together many smaller molecules. There are four main categories to know about...
LIPIDS
are the fats and oils. All cell membranes are built from lipid & protein.
CARBOHYDRATES include the sugars and starch.
Lipids are used as a way to store excess energy food. Carbohydrates can be converted to fat for storage.
monosaccharides
(mono = one) are simple sugars such as glucose C6H12O6
disaccharides (di = two) are sugars made from TWO monosaccharides joined together, such as “table sugar” (sucrose).
polysaccharides (poly = many) are huge molecules made from thousands of sugar molecules joined in chains or networks. Examples are: Starch... made by plants, to store excess sugar. Glycogen... made by animals, to store sugar. Cellulose... made by plants as a structural chemical. The CELL WALL of a plant cell is made from cellulose. Disaccharide Monosaccharide sugar molecules
PROTEINS are the main structural chemicals of organelles, cells, bone, skin & hair. Life is built from protein. Proteins are polymers, made from amino acid molecules joined in chains.
sugar
Amino acid molecules
Polysaccharide. Small part of a Starch molecule
Part of a protein molecule... a chain of amino acids
Uses of Carbohydrates Sugars are energy chemicals. Glucose is made by plants in photosynthesis, and is the “fuel” for cellular respiration to make ATP to power all cells. Starch & Glycogen are polymer molecules used to store sugars as a food reserve. Starch is the main nutrient chemical in the plant foods we eat. Cellulose & Lignin are polymers of sugar used by plants structurally. Cellulose makes the tough cell wall of all plant cells. Lignin is a strong material used to reinforce the walls of “veins” in plants. Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
NUCLEIC ACIDS
(DNA & RNA)
are the most complex of all. DNA is the genetic information of every cell. RNA is the “messenger” sent out from the nucleus to control all cell activities. DNA is a huge polymer of sugars, phosphate and “bases” coiled in a double helix shape. 8
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Identifying Chemicals in Tissues
The Structure of the Cell Membrane
You may have done laboratory work to learn some simple chemical tests which identify important substances. These tests all rely on a “reagent” which changes colour.
The electron microscope and other modern analysis methods have revealed the structure of the membranes which surround a cell and form most of the cell organelles.
To keep it simple (K.I.S.S.), learn these:
The membrane is extremely thin; just two molecules thick. The basic chemical unit is a “phospholipid” molecule; a lipid (fat) with phosphate groups attached. Each molecule has two distinct ends; one which is attracted to water molecules (“hydrophilic”) and the other is repelled by water (“hydrophobic”). “Hydro”=water. “philic”=to like. “phobic”=hate / fear.
Cell Chemical Glucose
Starch
Protein
Test Colour in Reagent Pure water Benedict’s solution Iodine solution Biuret
Positive Result
pale blue
yellow or orange
yellow brown
dark blue or black
blue
MEMBRANE STRUCTURE
One phospholipid
Outside of cell
hydro-p philic -p phobic
purple
You will have used one or more tests on living tissue and examined the cells with a microscope. Inside of cell
For Example: if tissue scraped from a fresh potato is mounted on a slide with a simple “contrast stain” (like methylene blue) the cells look like this:
Double layer of phospholipid molecules
POTATO CELLS
Two layers of phospholipids form each membrane. The molecules cling to each other, and line up with their hydrophilic ends outwards. The water-loving ends are attracted to the watery environment both inside and outside the cell.
Organelles faintly visible Cell walls
Their hydrophobic ends are repelled from the watery surroundings, and cling together inside the membrane itself.
If a drop of iodine solution is added, the same cells change as shown:
It is like a thin layer of oil floating on water. It is fluid and flexible, but clings together forming an unbroken “skin” on the surface.
POTATO CELLS WITH IODINE Organelles turn black
Other molecules are embedded in the phospholipid bilayer. They are mostly proteins, many with carbohydrates attached.
This indicates the presence of starch inside the organelles (these are storage vacuoles)
Membrane proteins
Once you have an understanding of the main chemicals that cells are made from, you need to realize that all of these substances, or their raw materials or waste products, are constantly moving in or out of a living cell.
These other molecules have various functions:
TO DO THIS CHEMICALS MUST CROSS THE CELL MEMBRANE Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
• “receptors” for messenger chemicals. • identification markers, so your body knows its own cells from any foreign invaders. • to help chemicals get through the membrane. 9
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How Chemicals Pass Through Membranes The cell membrane as the boundary of a cell is a bit like growing a plant hedge as the boundary of a field. It stops the cows and horses getting out, but a mouse, or a lizard, can easily crawl through it. Similarly, a membrane is “semi-permeable”; it prevents most (especially large) molecules getting through, but allows others to pass through easily. Small molecules like water (H2O), oxygen (O2) and carbon dioxide (CO2) pass freely through the membrane like a lizard through a hedge. To understand how this happens, you must learn about the processes of DIFFUSION & OSMOSIS.
Diffusion Diffusion occurs in every liquid or gas because the atoms and molecules are constantly moving. The particles “jiggle” about at random in what is called “Brownian motion”. (Named for its discoverer Robert Brown, the same man who discovered the cell nucleus.)
In a living cell, there is often a “concentration gradient” from the outside to the inside of the cell. For example, because a cell keeps consuming oxygen for cellular respiration, the inside of the cell usually has a low concentration of O2 dissolved in the water of the cytoplasm. On the outside, there may be a lot of O2.
Imagine a water solution containing a dissolved chemical, but it is NOT evenly distributed... it is more concentrated in one place than elsewhere. As the molecules jiggle about at random, they will automatically spread out to make the concentration even out. This process is called DIFFUSION. High concentration
DIFFUSION of SMALL MOLECULES into a CELL If the molecules can cross the membrane, diffusion will cause them to move from higher to lower concentration. Higher concentration outside cell
To start with, the dissolved material is not evenly distributed.
Lower concentration inside
Lower concentration Diffusion causes the dissolved solute to spread out uniformly.
DIFFUSION DRIVES MOLECULES THROUGH THE MEMBRANES along the concentration gradient.
Equal concentration throughout
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Osmosis Osmosis is a special case of diffusion, which occurs when the concentration gradient involves dissolved molecules or ions which CANNOT get through the membrane. For example, consider a cell which is The opposite situation can also happen. surrounded by a solution containing a lot A cell’s cytoplasm contains many of dissolved sugar. The sugar cannot dissolved chemicals. If the outside diffuse through the membrane to equalize environment around the cell is more the concentrations. In such a situation, watery (less concentrated in dissolved water (which can go through the substances) then osmosis will cause membrane) will diffuse toward the high water to diffuse inwards. H2O Dissolved chemicals sugar concentration, as if attempting to H2O cannot diffuse out... equalize by diluting the sugar. OSMOSIS High concentration of sugar outside cell
Water diffuses OUT of cell
H2O H2O
H2O Sugar cannot get in through the membrane
...so water diffuses into the cell.
H2O
This is how plants absorb water into their roots, even when the soil seems almost dry.
In this case, the cell will lose water and might shrink and shrivel up. This can be a problem for animals living in salt water.
This can cause cells to “pump up” with water and helps maintain their shape. It can also cause problems for organisms living in fresh water environments.
Comparison of Diffusion and Osmosis Diffusion is the movement of dissolved chemicals from an area of higher concentration toward a lower concentration area. The movement follows the “concentration gradient” of the molecules in question. Osmosis is a special case of diffusion. It is the diffusion of WATER through a semi-permeable membrane, against the concentration gradient of solutes. It occurs when the solutes cannot penetrate the membrane, but the water can. Other Ways Substances Get Through Membranes Diffusion and Osmosis are vitally important for many chemicals (especially water) to get in and out of cells. Diffusion and osmosis happen automatically and without the cell having to use any energy. We say these are “passive transport” processes.
Cells have other ways to deliberately move substances across the membrane apart from diffusion and osmosis. One such process involves the membrane proteins carrying things. These “other” ways to transport materials across membranes require the cell to use energy (ATP from cellular respiration) to move substances. We say these are “active transport” processes. You do not need to know the details at this stage.
What about all the other important chemicals which cannot get through the membrane? Many proteins, carbohydrates and other molecules regularly move into or out of cells. How do they get in or out? Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
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The Importance of the Surface Area to Volume Ratio Why are cells so small? The answer requires a mathematical study... Consider this series of cubes of increasing size:
2 unit sides
1 unit sides
4 unit sides
3 unit sides
Surface Area: Six squares, each 1x1
Surface Area: Six squares, each 2x2
Surface Area: Six squares, each 3x3
Surface Area: Six squares, each 4x4
SA = 6x1x1 = 6 sq.units
SA = 6x2x2 = 24 sq.units
SA = 6x3x3 = 54 sq.units
SA = 6x4x4 = 96 sq.units
Volume = lxbxh = 1x1x1 = 1 cu.unit
Volume = lxbxh = 2x2x2 = 8 cu.unit
Volume = lxbxh = 3x3x3 = 27 cu.unit
Volume = lxbxh = 4x4x4 = 64 cu.unit
Ratio of SA to Volume
Ratio of SA to Volume
Ratio of SA to Volume
Ratio of SA to Volume
SA/V = 6 / 1
SA/V = 24 / 8
SA/V = 54 / 27
SA/V = 96 / 64
SA = 6 vol
SA = 3 vol
SA = 2 vol
SA = 1.5 vol
Notice that as the cubes get larger:
But, all cells have to get whatever they need in through their cell membrane, and the size of the membrane is all about surface area.
• Surface Area increases, and... • Volume increases, but...
As any cell gets bigger, it becomes more and more difficult for it to get enough food, water and oxygen because its SA/Vol. ratio keeps shrinking. Getting rid of waste products also becomes more difficult.
• SA / Vol Ratio DECREASES, because the volume grows faster than the surface area. This pattern is the same for any shape... as any shaped object gets bigger, the ratio between its Surface Area and its Volume gets smaller.
Large cells are impossible... all singlecelled organisms are microscopic, and all larger organisms are multi-cellular. The only way to be big is to have lots of small cells.
What’s this got to do with cells? The amount of food, oxygen or other substances a cell needs depends on its volume... the bigger the cell, the more it needs according to its volume.
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Cells must feed their Volume, through their Surface Area
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Worksheet 2
Chemicals & The Cell Membrane
Fill in the blank spaces. The cell membrane is made from a double layer of (o)...................................... molecules, with various proteins embedded.
Simple, small molecules and ions (e.g. water, nitrate) are known as (a)........................ compounds, as opposed to “organic” compounds which are based on the element (b)................, and include:-
The membrane is said to be “semi(p)........................................”
• (c)............................... which are polymers of amino acids
Diffusion is a process where molecules move from a place of (q)............................ concentration, towards a (r)...................... concentration.
• Lipids, which are found structurally in the cell (d)...................................... and are also used as (e)................................ ..........................................
Osmosis is the diffusion of (s).......................... molecules only, against the solute concentration (t)........................., when the solute is unable to get through a membrane.
•(f)......................................... which include the sugars & starches. One of this group, glucose, has chemical formula (g).............................. and is the “food” made during the process of (h)................................... It is also the fuel for (i)..................................... (organelle) to make ATP.
Diffusion & Osmosis are both examples of (u)................................. transport, because the cell does not need to use (v).............................. to make things move.
• Nucleic acids, of which (j).................... is the best known.
As any shape gets larger, its (w)......................................... ratio gets smaller. This is why all cells are small. A large cell needs chemicals in proportion to its x).............................................. However, it must get substances in through its y)............................................, the size of which is measured by its z)............................ .....................................
If Benedict’s solution turns from blue to yellow, this proves that (k)....................................... is present. Protein can be identified by (l).................................... reagent, and if starch is present iodine solution will turn from (m) .................... to (n).......................
The only way for living things to be large, is to have aa).................................... cells, NOT by having ab)............................ cells. WHEN COMPLETED, WORKSHEETS BECOME SECTION SUMMARIES
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Worksheet 3 Practice Questions (Sections 1 & 2) 8. A food substance, which may be a mixture of various organic chemicals, was tested with the following results: Iodine solution gave a yellow, brown colour. Biuret reagent gave a purple colour. Benedict’s reagent resulted in a pale blue colour.
Multiple Choice 1. The man credited with the discovery of the cell nucleus was: A.Robert Hooke. B. Anton van Leeuwenhoek. C. Robert Brown. D. Louise Pasteur.
From these results you would conclude that the food contains: A. protein, but no starch or sugar. B. starch, but no protein or sugar. C. sugar and protein, but no starch. D. sugar and starch, but no protein.
2. The organelle least likely to be seen with a light microscope is: A. Mitochondrion. B. Vacuole. C. Nucleus. D. Chloroplast.
Longer Response Questions
3. The cell structure never found in an animal cell is: A. cell membrane. B. cell wall. C. endoplasmic reticulum. D. golgi body.
Mark values given are suggestions only, and are to give you an idea of how detailed an answer is appropriate. 9. (3 marks) Compare the light microscope to the electron microscope in terms of how each forms an image, the magnification, and the resolution of each.
4. The function of the ribosomes can be described as: A. storage of genetic information. B production of ATP. C. packaging of substances for secretion. D. manufacture of proteins.
10. (2 marks) Using either the nucleus or mitochondrion as your example, discuss the way that the structure of the organelle relates to its function.
5. Starch, glycogen and cellulose are all: A. proteins, composed of amino acids. B. nucleic acids, related to DNA & RNA. C. sugars, of the carbohydrate group. D. polymers of glucose.
11. (4 marks) Using examples, discuss the difference between the “organic” & “inorganic” chemicals found in living cells.
6. The diagram shows a cell surrounded by a solution which has a high concentration of large molecules.
12 (2 marks) The cell membrane is described as being “semipermeable”. Explain what this means.
You might expect: A. solute molecules to diffuse into the cell. B. water to diffuse into the cell. C. water to diffuse out of the cell. D. solute molecules to diffuse out of the cell.
13. (4 marks) Compare the processes of diffusion and osmosis, identifying what substances are involved and the direction of movement (compared to any “concentration gradient”)
7. A brick was smashed into smaller pieces with a hammer. It would be true to say that all the brick pieces, when compared to the original brick, have: A. larger total volume. B. larger SA/Vol ratio. C. smaller total surface area. D. smaller SA/Vol ratio. Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
14. (4 marks) Explain why all living cells have to be very small in size.
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3. NUTRITION IN PLANTS & ANIMALS Autotrophs & Heterotrophs
Photosynthesis & Cellular Respiration
An autotroph is an organism that makes its own food. All plants are autotrophic, making their own food by photosynthesis.
You will have noticed that these two vital processes, when written as summary equations, are exact opposites. Light energy
Any organism that cannot make its own food must be a heterotroph. All animals are heterotrophic, and so are the fungi and most bacteria. A heterotrophic animal eats plants or other animals which have eaten plants, and so on according to the food chain involved.
CARBON DIOXIDE
Photosynthesis in Plants
+
All plants make their own food from the simple, low-energy raw materials water (H2O) and carbon dioxide (CO2) using the energy of sunlight, to make the high-energy sugar glucose (C6H12O6), with oxygen gas (O2) as a by-product. green pigment in chloroplasts of plant cells
ligh te ner gy
WATER + CARBON DIOXIDE
from soil
6H2O
from air
+
6CO2
chlorophyll
WATER
ATP
C6H12O6
to air
+
6O2
MITOCHONDRIA - site of cellular respiration
Photosynthesis makes all the food on Earth, for all the food chains. It also makes all the oxygen in the atmosphere for us animals to breathe. For these two reasons, photosynthesis has to be the most important biological process on the planet.
PHOTOSYNTHESIS in the CHLOROPLAST Phase 2 In the stroma, a cycle of reactions builds glucose from CO2 and the hydrogen from water
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OXYGEN
The Most Important Process on Earth
There are 2 main stages, which take place in different parts of the chloroplast, as summarized below.
Phase 1 In the grana, chlorophyll absorbs light energy and uses it to split water into hydrogen and oxygen
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As you learned in Topic 1, in all ecosystems there is a constant input and flow of energy via the food chains, while the chemicals such as H2O, O2, and CO2 simply get re-cycled over and over.
This brief summary equation is very deceptive. Photosynthesis actually occurs as a complex series of chemical steps inside the chloroplast.
ligh t
GLUCOSE
What is really happening is ENERGY FLOW through the food chains of an ecosystem. Photosynthesis captures the energy of light and stores it in a high energy food compound like glucose. Cellular respiration releases that stored energy in the form of ATP which can power all cellular and life activities... growing, moving, keeping warm etc.
GLUCOSE + OXYGEN
highenergy sugar (food)
CHLOROPLAST - site of photosynthesis
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Glucose can also be converted chemically into lipids... fats and oils, since they contain exactly the same chemical elements (carbon, hydrogen & oxygen only - CHO).
What Happens to Glucose in a Plant? If photosynthesis only makes glucose, where do all the other biological chemicals in a plant come from? Glucose is a monosaccharide sugar, a member of the carbohydrate group. It is easy for a plant to convert glucose into other types of carbohydrate. GLUCOSE molecules
GLUCOSE
LIPIDS (oils)
Making proteins and nucleic acids is more difficult, since these contain additional chemical elements, especially nitrogen, phosphorus and sulfur.
Other sugars, such as sucrose joined in pairs
’s 00 n) 10 tio in risa ed e in m jo oly (p
This is where the “minerals” such as nitrate, phosphate and sulfate come in. Soil minerals are often called “plant nutrients”, and a gardener may say he/she is “feeding” the plants when applying fertilizer, but these minerals are NOT food. They are the essential ingredients needed so plants can make proteins and DNA etc, from the real food... glucose.
CELLULOSE for building new cell walls
STARCH for storage of food
Soil minerals
nitrate, sulfate etc
In fact, plants convert glucose to STARCH so rapidly that the chloroplasts in a plant leaf become packed with starch grains when it is photosynthesising. THIS IS THE BASIS OF EXPERIMENTS YOU MAY HAVE DONE
GLUCOSE
chemical conversion
Amino acids
PROTEIN
Polymerisation
Experiments with Photosynthesis The classic experiment you have probably done, is to partly cover a leaf with light-proof aluminium foil, and then expose it to light for several days. The aim is to prove that light is necessary for photosynthesis. Lig ht
No light, no starch
Experimental Set-u up
Alu min ium foil
Result Iodine test shows lots of starch here
After several days, the leaf is decolourized (so the test can be seen more easily) and then tested with IODINE solution.
Sure enough, you probably found that any part of the leaf exposed to light turned black when soaked in iodine, while parts under the foil did not go black.
Why Iodine? It detects STARCH, not glucose. This proves that any part of a leaf allowed to photosynthesise will build up a store of starch from the glucose it makes. The first product of photosynthesis is glucose, but it is rapidly converted to other things.
As explained above, the glucose produced by photosynthesis is immediately converted to starch. The iodine test is used because it is the test for starch. Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
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Structure & Function... How Plants Get Water & Carbon Dioxide In order to photosynthesise, plants must collect water and carbon dioxide. In a land plant, water is collected by the roots from the soil, and carbon dioxide is collected from the air into the leaves. Both roots and leaves require special structures to gather these vital chemicals. Plants Absorb Water through special outgrowths on the roots called “root hairs”.
The actual absorption of water is achieved by osmosis. The cell cytoplasm has a higher solute concentration than the water solution in the soil, so water diffuses into the cell through the cell membrane of the root hair cells.
Each root hair is part of one, very elongated cell. Root hairs help absorption of water by greatly increasing the surface area of the root in contact with the soil.
Once absorbed into the root hair cells, water diffuses from cell to cell towards the central xylem tubes which carry the water (and dissolved minerals) upwards to the leaves. This upward flow is achieved by the plant constantly allowing water vapour to evaporate from each leaf (“Transpiration”). This creates a “suction” at the top of the xylem tube, rather like drinking through a straw.
MICROSCOPIC VIEW NEAR A ROOT TIP LONGITUDINAL TRANSVERSE SECTION SECTION XYLEM TUBES
Phloem tubes
ROOT HAIRS
Alongside the xylem tubes are the phloem tubes which carry food from the leaves to any part of the plant which cannot photosynthesize... especially down to the roots. Together the xylem and phloem tubes form the “veins” in a plant. They not only carry substances around the plant, but are important as reinforcement and support structures.
Epidermis layer
Outgrowths from epidermis cells
The Importance of Surface Area It is generally true of many processes such as absorption and chemical reactions, that the greater the surface area, the faster the rate of the process. You may have done a simple experiment similar to this:Same quantity of solid calcium carbonate on each spoon
Lumps
Powder Both lumps and powder react with acid in exactly the same way, but you would observe that the powder reacts faster. Same quantity of same strength acid
The more finely divided a solid is, the greater its surface area, so the powder has more surface area than the lumps. This experiment demonstrates the principle that things happen faster when more surface area is available for reaction or absorption.
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The Structure of the Leaf A plant leaf is a factory for photosynthesis. A typical leaf is built so that every part of its design is suited to the achievement of that one objective... making food. It is a classic case of Structure matches Function. The “veins” contain xylem tubes for carrying water and minerals up from the roots, and phloem tubes for carrying manufactured food away. Being specially reinforced with tough “lignin”, the veins also support the flimsy leaf, and keep it in shape and positioned to catch maximum light.
A leaf is generally broad, flat and thin. This gives it maximum surface area for absorbing light and carbon dioxide from the air. A leaf is thin enough that light penetrates to reach each layer of cells within, for maximum photosynthesis.
The Palisade Layer of cells are tightly packed in an orderly row immediately under the top epidermis where there is maximum light. Each cell contains many chloroplasts. This is the “engine room” for photosynthesis.
The cuticle is a layer of clear, waxy material. It allows light through, but is waterproof to prevent excessive water loss.
MICROSCOPIC CROSS SECTION THROUGH A LEAF
The epidermis layer of cells is transparent like a window, to let light through to the cells underneath. Veins run throughout each leaf. The xylem tubes bring water and minerals from the roots and release them into the spongy layer. From there, some diffuses into the cells for photosynthesis, while the rest evaporates through the stomates.
The Spongy Layer has very loosely packed cells, with lots of spaces around them. This allows gases (CO2 & O2) and water to easily move around by diffusion. The lower leaf surface has many openings, called “stomates”. These allow: • water to evaporate from the leaf (Transpiration). This ensures that water and minerals continue to be “sucked up” from the roots. magnified and rotated to surface view
• CO2 to diffuse into the leaf for photosynthesis. • O2 to diffuse out of the leaf into the air. A magnified surface view of a stomate is shown.
There are phloem tubes as well, which collect the food manufactured in the leaf cells and carry it away to feed other parts of the plant, such as roots, stem and flowers which might not be able to photosynthesise. Veins also act as reinforcing, helping to keep the flimsy leaf deployed to catch maximum light.
Each stomate pore is an opening formed between two special “guard cells”. These cells can change shape to open the pore, or close it up to minimize water loss in dry conditions. The guard cells change shape by using osmosis to either pump-up full of water (pore open), or deflate and shrivel (pore closed).
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Pore opening
SURFACE VIEW OF A STOMATE
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Nutrition in Animals Animals are Heterotrophs. They must eat energy-rich food made by other organisms, either plants or other animals. Starch molecule
The food an animal eats is composed largely of complex carbohydrates, proteins and fats which must be digested before being absorbed into the body and used by the cells. Digestion involves chemically breaking large molecules down into smaller units which can be carried around the body and transported across cell membranes.
ENZYME
Sugar molecules
ENZYME
Protein molecule
Amino acid molecules
HUMAN DIGESTIVE SYSTEM
Salivary Glands. An enzyme in saliva begins digesting starch.
Chewing the food begins the digestion process. Chewing breaks food into smaller pieces with greater surface area, so digestive enzymes can attack it faster.
Oesophagus carries food to the stomach.
Liver receives and processes digested nutrients after they are absorbed into blood stream.
Stomach churns food with acid. Enzymes digest proteins in food
Gall bladder adds bile to dissolve fats so enzymes can digest them.
Pancreas adds a cocktail of enzymes to futher digest food
Small Intestine completes digestion with a cocktail of enzymes, then absorbs nutrients into the blood stream. Inside, it has many folds or “villi” which increase surface area for absorption.
Large Intestine absorbs water, vitamins & minerals into blood stream.
Rectum stores undigested wastes (faeces) for later elimination.
Caecum & Appendix have no special functions in humans Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
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Different Animals Have Different Systems The digestive systems of different animals are often quite similar, but certainly not identical. Once again, the principle of “structure matches function” can be noticed.
Digestion in Herbivores
Digestion in Carnivores
Plant-eaters face a problem... a lot of plant material has a low nutrient value and contains a lot of fibrous matter which is difficult to digest. The fibre is mostly the plant cell walls, made of cellulose... a polymer of glucose, but animals lack the necessary digestive enzymes to break the cellulose down.
Flesh eaters don’t need such huge digestive systems. Their food is much more concentrated in its nutritional value, and relatively easy to digest. Carnivores usually have:• sharp, tearing teeth to cut flesh into chunks for swallowing... chewing is not so important.
Herbivores usually have:• flat, grinding teeth to chew the food thoroughly to increase the surface area exposed to enzymes. • relatively long intestines and caecum, for more surface area and longer time available for digestion. • bacteria living in their gut which have enzymes to digest cellulose. This is an example of “mutualism”.
• relatively short intestines. • a highly elastic stomach, which allows them to swallow a large meal. The stomach acid and enzymes are vital for digesting their high protein meat diet.
Huge Caecum
Grinding teeth
Stomach Long Small Intestine
Long Large Intestine
Digestion in a Nectar Feeder Some animals eat a diet that requires very little digestion at all. Many birds (eg honey-eaters, humming birds) and insects (eg butterflies) feed largely on the sugary nectar of flowers. Sugar does not require any digestion at all, so their digestive system can be very short and simple. A short-lived butterfly only needs nectar for the energy its sugar supplies, but a bird needs more nutrients. Most eat the plant pollen which is rich in protein and oil. Therefore, their short little digestive system does need to do some work, apart from simply absorbing sugar. Nectar & Pollen feeding lorikeet
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Tearing teeth Stomach more important
Shorter intestines
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Worksheet 4
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Nutrition in Plants
Amino acids can then be joined together to form (p)..................................
Fill in the blanks. (a)....................................... (e.g. plants) are organisms that can make their own food, while (b)................................ (such as animals) cannot.
The structures mainly responsible for absorbing water into a plant are the (q)....................................... which are outgrowths of root cells and greatly increase the (r)........................................ of the roots. Water is absorbed by the process of (s)............................................ then transported up to the leaves through (t).................................. tubes.
The process of photosynthesis can be summarized as (c)................. + (d).................................... (e).................. + (f).....................
In a leaf, there are many examples of “structure matching function”, such as: • The shape of the leaf gives maximum surface area for (u)....................................
Photosynthesis occurs in the (g)................................ (organelle) in plant cells. The green pigment (h).................... absorbs (i)...................... energy for the process. This energy is stored as chemical energy in the (j)................................. molecules produced.
• The (v)................................................ layer of cells, packed together & full of chloroplasts for maximum photosynthesis.
Thousands of glucose molecules can be joined together by the process of (k)..................... to form (l).......................... (used for storage) or cellulose which is used to build (m).....................................
• The “spongy layer” of loosely packed cells to allow (w)........................................ • The (x)..................................... which can open and close and allow water to evaporate (called (y)............................) and to let the gas (z).................................. in for photosynthesis.
Glucose can also be chemically converted into (n).................................. To convert sugar to amino acids, the plant needs a supply of (o)...........................................
Worksheet 5 Nutrition in Animals
Digested nutrients are absorbed into the blood stream from the (f)........................., then carried in the blood to the (g)........................... for processing.
Fill in the blanks Animals have to digest the food they eat. This is carried out by digestive (a)............................ which, for example, break starch into (b)........................... and proteins into (c)........................................
Herbivorous animals usually have: • (h)...................... teeth to chew thoroughly • relatively (i)........... intestines and caecum • mutualistic (j).................... living in their gut to help them digest (k)........................... which is a major part of their diet.
There are 4 organs in the mammal digestive system that produce digestive enzymes. Name them all. (d)........................., ................................ ........................... and ...............................
Compared to them, carnivores usually have (l).......................... teeth and relatively (m)............................ intestines
Digestion begins with chewing food which increases the (e)............................. of the food, so enzymes can attack it faster. Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
Nectar feeders, such as (n)....................... have digestive systems which are very (o).......................... and ......................... 21
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Worksheet 6 Practice Questions (Section 3) Multiple Choice
Longer Response Questions
1. The chemical raw materials needed for photosynthesis are: A. glucose and oxygen. B. water and carbon dioxide. C. carbon dioxide and oxygen. D. water and glucose.
Mark values given are suggestions only, and are to give you an idea of how detailed an answer is appropriate. Answer in the spaces provided. 8. (2 marks) Differentiate between “autotrophs” & “heterotrophs”, including examples in your answer.
2. The chemical “ATP” is best described as: A. the carrier of genetic information. B. the product of cellular respiration. C. the absorber of light for photosynthesis. D. a waste product from the mitochondria.
9. (5 marks) a) Summarize the process of photosynthesis by a word equation, including the energy source.
The following sketch shows a cross-section through a leaf. Use the diagram for Q. 3 & 4 P Q
b) Give two reasons why photosynthesis can be considered the most important biological process on Earth.
S
R T
3. A structural feature which helps the functioning of the leaf is that the cells at “P”: A. are transparent B. are loosely packed C. contain many chloroplasts D. open up to let gases in/out
10. ( 5 marks) In experiments on photosynthesis, the presence of starch in leaves is often taken as proof that photosynthesis has taken place. a) Explain why it is starch, not glucose, that the leaves are tested for.
4. The “guard cells” are labeled A. Q B. R C. S D. T b) Outline the method of testing for starch in a leaf, including any preliminary treatment(s).
5. Soil minerals such as nitrates, phosphates and sulfates are essential to a plant for which purpose? A. To provide energy. B. To make starch from glucose. C. As raw materials for photosynthesis. D. To make proteins from glucose.
11. (4 marks) Discuss the relationship between structure and function shown by the leaf cell layers known as the “palisade layer” & the “spongy layer”.
6. In a mammalian digestive system, the main chemical digestion in the stomach involves the breakdown of: A. starch. B. protein. C. lipids. D. sugars.
12. (3 marks) Briefly outline how the length and complexity of an animal’s digestive system is related to its diet. Refer to 3 different types of diets in your answer.
7. An animal with large, flat, grinding teeth and a very large caecum (a blind “pocket” of the intestine) probably eats mainly: A. nectar, pollen and flowers. B. the flesh of other animals. C. plant leaves and grass. D. fish & other seafood. Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
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4. GAS EXCHANGE & INTERNAL TRANSPORT Organisms Need What Cells Need
Gas Exchange in Animals
Every living cell, plant or animal, has certain requirements:-
There are many ways that animals carry out gas exchange. This section will compare four different systems... mammal, frog, fish and insect.
FOOD in
WATER in
OXYGEN in
Lungs in a Mammal Using the human as a typical example: HUMAN RESPIRATORY SYSTEM
Lungs are not hollow, but sponge-llike
Trachea (Windpipe)
WASTE PRODUCTS such as CO2 must be excreted
A single-celled organism exchanges these chemicals with the environment directly through its cell membrane. However, in all multicellular organisms most of the cells are located deep within the body. There have to be body systems to:• absorb nutrients, water and oxygen • excrete wastes • transport all these chemicals between the cells and the environment.
Each bronchus sub-d divides into Bronchioles Each bronchiole ends in a cluster of tiny air sacs... the Alveoli
Each Alveolus has a wall just 1 cell thick, and the internal surface is kept moist
In animals the body systems involved are: Digestive system absorbs nutrients and water. Respiratory system (e.g. lungs) exchanges gases, absorbing oxygen, and excreting carbon dioxide. Excretory system (kidneys) removes other wastes such as urea. Circulatory system (blood, heart, veins etc) transports all these things around the body.
Blood flow
Blood capillary
AIR flows in and out
Bronchiole
Plants also have systems for exchanging gases, and for transporting substances around their bodies.
O2 CO2
The lung is not just a hollow space like a balloon. If it was, the surface area for gas exchange would be about the size of this page. By dividing into millions of alveoli, the total surface area inside your lungs is about the same size as a tennis court!
Requirements for Gas Exchange Plant or animal, large or small, all organisms need to exchange gases with their environment. Efficient gas exchange requires:• a large surface area in contact with the environment.
The inside surface is always moist, for gases to dissolve and diffuse, and each alveolus is in intimate contact with a blood capillary to transport the gases to and from the body cells.
• a moist gas exchange membrane because the gases must dissolve in water before passing through the membrane by diffusion. • close contact with the blood supply (or other transport system) to carry gases between cells and the gas exchange organs. Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
Bronchi (sing: bronchus) carry air to each lung
The requirements for efficient gas exchange have been met. 23
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Gas Exchange in a Frog
Gas Exchange in a Fish
Amphibians hatch from their egg as “tadpoles” which live in water and breathe with gills. Later they undergo metamorphosis and develop into the adult form which breathes with lungs.
Land-dwelling, air-breathing animals always must have their gas exchange organs inside their bodies so the moist membranes won’t dry out. In water this can’t happen, so a fish’s gills are exposed to the water environment, but shielded by a tough “gill cover” to protect the delicate breathing organs. Gases are dissolved in the water
However, a frog’s lungs are much simpler than a mammal’s, and don’t have as many alveoli.
Gills
under gill cover
The gills are a series of feather-like plates around which the water flows. Each gill plate consists of thousands of tiny “filaments” each one a thin leafshaped structure packed with blood capillaries.
FROG RESPIRATORY SYSTEM
WATER FLOW
BLOOD FLOW IN CAPILLARIES
Mouth and throat cavity are moist & lined with blood vessels
Simple Lung
Water out
Water in
Doesn’t this mean less surface area and less efficiency? Yes, but a “cold-blooded” frog doesn’t need to carry out cellular respiration just to make body heat the way mammals do. So the need for O2 intake is a lot less. Also, the frog doesn’t just do gas exchange in its lungs...
FISH BREATHE WITH GILLS
Moist Skin also acts as a gas exchange surface Blood flow
The frog makes up for its inefficient lungs by carrying out gas exchange through other body surfaces which are kept moist and are lined with blood vessels... its mouth and throat cavity and the skin all over its body.
WATER FLOWS ACROSS & BETWEEN FILAMENTS
GILL FILAMENTS
Gills have to be highly efficient, because remember from Topic 1, that the level of oxygen dissolved in aquatic environments is much lower than the concentration in air.
Gas Exchange in an Insect Insects don’t have lungs or gills. Along the sides of their bodies is a series of holes called spiracles. Each spiracle allows air to move into a network of tubes (“trachea”) which infiltrate their whole body.
This system is quite efficient in a small animal, but rapidly becomes inadequate as the animal grows larger, because the Surface Area to Volume Ratio gets smaller.
Spiracles
That’s why there’s no such thing as a really big bug! Hollywood fantasies cannot actually happen. Study each system again... mammal, frog, insect, fish and note of how each system achieves the three essential features of any gas exchange system...
Trachea The trachea tubes are moist inside for gas exchange. Gases diffuse directly to the body cells, which are never far from a trachea tube. The network of tubes increases the surface area for gas exchange.
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• LARGE SURFACE AREA • MOIST MEMBRANE SURFACE for diffusion • CLOSE CONTACT WITH BLOOD STREAM or body cells.
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Internal Transport in Animals
Open Circulation Systems
Once nutrients and gases have been absorbed into the body, they need to be transported to every body cell. In animals this is the job of the Circulatory System, consisting of the heart, blood vessels and the blood itself.
Invertebrate animals (including insects, worms & snails) have much simpler circulatory systems in which the “blood” (or a fluid doing the same job) does not always stay inside a blood vessel. OPEN CIRCULATION IN AN INSECT Schematic diagram
Once again, different types of animals have all sorts of variations, but in this section only a broad comparison between two general types of system will be made.
Arteries
Closed Circulation Systems All vertebrate animals (fish, amphibians, reptiles, birds and mammals) have a blood system that is “closed”... the blood is always flowing inside a blood vessel, pumped around by the heart.
Heart pumps “blood” fluid
CLOSED CIRCULATION IN A MAMMAL Schematic Diagram
CO2
O2
Veins
Artery
Capillary network in Lungs
Blood fluid flows directly among body cells
Veins
Vein
Fluid slowly collects back into veins. Wastes (but not CO2) are taken away for excretion, and blood returns to the heart.
HEART pumps blood
The “open” system is not very efficient, because the blood is not forced to keep flowing through blood vessels as in a closed system.
Arteries
Alveoli (air sacs) in lungs
Circulatory fluid flows out of blood vessels
However, in a small insect, with its separate gas exchange system which is not dependent on blood flow, this is obviously quite adequate... after all, insects are the most numerous animals on the planet! Capillary network in body
Body cells receive O2 & nutrients, and get rid of CO2 & other wastes
This system is highly efficient because the blood can be kept flowing within the vessels, guaranteeing a steady flow of nutrients, gases and wastes between body cells and the outside environment. This efficiency allows vertebrates to grow very large and still function perfectly despite the poor SA/Vol ratio of a large body. Be aware that fish, amphibians and most reptiles do not have a system quite the same as a mammal, but in all cases the system is “closed”. Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
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Internal Transport in Plants Plants have two separate systems for transporting substances inside their bodies...
Xylem
Phloem
tubes carry water and dissolved minerals from the roots to the leaves.
Plants have a separate set of tubes for transporting sugars and other food nutrients; the phloem tubes.
Hollow, dead cells, joined end-tto-e end forming a tube
While the xylem tubes are formed from dead cells, the phloem are living cells joined end-to-end. The ends of each cell are perforated (“sieve plates”) so each cell is open into the next so they form a continuous tube. The movement of food via the phloem is called “Translocation”.
Cell walls re-iinforced with rings and spirals of lignin
It is an “active transport” operation, meaning that the plant has to use energy to cause the material to flow.
sugars are actively transported in the cytoplasm of the cells
PHLOEM CELL
alive and filled with cytoplasm. Movement of cytoplasm carries sugars through each cell
The upward movement of water in xylem tubes happens without any effort by the plant... it is “passive transport”. The evaporation of water from the leaves through the stomates, (“Transpiration”) causes a “suction” effect at the top of each xylem tube. This draws more water from the roots.
Sieve plate between cells
Rate of Transpiration You may have done experiments on transpiration to measure it, and the factors which affect its rate. A common way to do this is with a “potometer”:-
“Companion cell”
has many mitochondria to provide ATP to the phloem cell
POTOMETER METHOD FOR MEASURING TRANSPIRATION The flow of liquid is caused by differences in osmotic pressure
Fresh plant shoots
Ruler measures movement of air bubble in tube
Glass tube filled with water. As Transpiration occurs from the leaves and sucks water up from below, an air bubble is sucked in at the end of the tube. A ruler gives a scale to measure rates of transpiration under different conditions.
A “companion cell” beside the phloem cell supplies ATP from cellular respiration to power the active transport in the phloem tube. Rubber tube (filled with water) connects glass tube to live plant shoot
While the xylem is a one-way flow system, the phloem system can carry food (especially sugars) in either direction.
Typically it is found that the rate of transpiration is increased by higher temperatures, air flow (wind), low humidity and increased light. (The effect of light is because when lit, most plants open their stomates to get CO2 in for photosynthesis. The open stomates then allow more transpiration.) Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
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If a lot of photosynthesis is occurring, the phloem will carry sugar to storage sites in roots or stem. If photosynthesis is not possible for an extended time, then the phloem will carry sugars back from the storage sites to feed the leaf cells, or supply a growing flower or fruit.
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The Use of Radio-isotopes to Study Transport Systems
Gas Exchange in Plants The structure and functioning of the leaf stomates was covered earlier.
The atoms of each chemical element are not all exactly the same. They have the same number of protons & electrons (that’s what makes them that element), but the number of neutrons in the atom may vary. Such atoms of the same element, but with a different number of neutrons, are called “isotopes”. Some isotopes are “radioactive” and give off nuclear radiations... hence “radio-isotopes”.
What about other parts of a plant?
Lenticels are simple structures on the stems and trucks of plants which allow gas exchange to the cells by simple diffusion from the air. Tightly packed stem cells
The radiation they give off can be detected by photographic paper or special instruments such as the “Geiger counter”. If a radio-isotope is introduced into a plant or animal, its transport through the body can be followed by monitoring the radiation the isotope emits.
Surface cells
Lenticel opening
This “tracer” technique is one of the more important methods used to study the movement of substances in living things. This is how a lot of our knowledge of transport systems has been discovered.
Loosely packed cells allow gases to diffuse in and out
For example: If a leaf is exposed to CO2 containing “carbon-14” (a radio-active isotope of carbon):
Root Hairs were covered earlier in connection
Radioactive CO2 absorbed by leaf
with water absorption. Because they increase the surface area of the roots, root hairs are important for gas exchange as well as water absorption. Oxygen in soil spaces, or dissolved in soil water simply diffuses into the root hair cells, and spreads to other root cells by further diffusion.
Soon, radiation is detected in starch grains in leaf cells.
Next, radiation is found in sugars in phloem tubes Later, it’s here
From studies like this we learn the details of the chemistry and transport systems inside living things
Later still, the radiation is detected in starch stored here
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Worksheet 7
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Gas Exchange & Transport in Animals Insects have a series of holes called (k).................................. along their body which lead into a network of tubes called (l)................................ This works OK for small insects, but means no insect can ever be really large because its (m)........................................... ratio would be too small for sufficient gas exchange.
Fill in the blank spaces & diagram labels. The 3 requirements for an efficient Gas Exchange system are: • large (a)................................................... • gas exchange membrane which is kept (b).............................. • close contact with (c)....................... ......
In a fish’s (n)........... there are thousands of leaf-shaped (o)..................... around which water flows. In each filament are blood capillaries in which blood always flows (p)............................ to the water flow. This “(q)...................................... current” flow is much more efficient.
In any gas exchange system, the gases move across the membrane by the process of (d)........................................... (e).............................
In a “(r).................................... circulatory system” the blood is always inside blood vessels, and kept circulating by the pumping of the (s)......................................
(g)..................................... .. (h)........................ (microscopic air sacs)
(f) ............................
(t)......................................... animals have “open circulatory systems” in which the blood leaves the blood vessels and flows directly in contact with the body cells.
Compared to a mammal’s lung, the lung of a frog is (i)......................... Frogs exchange gases through their (j)......................... and ............................... as well as lungs.
Worksheet 8
Gas Exchange & Transport in Plants
Fill in the blanks It is increased by factors such as (h)........................... and (i)........................
Gases exchange in a plant occurs through the (a).................................... of the leaves, and via the (b).............................. of stems, and the (c)............................. in the roots.
Food nutrients are carried by the (j)......................................... tubes. This transport is called (k)................................ and is considered “active” transport because (l)................................................. .............................. In contrast, xylem transport is (m)..................................................
Xylem tubes carry (d)................................ and ........................ from (e)....................... to (f).............................. The evaporation of water from the leaves is called (g).................................... Preliminary Biology Topic 2 “Patterns in Nature” copyright © 2005-2 2008 keep it simple science www.keepitsimplescience.com.au
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Worksheet 9 Practice Questions (Section 4) 6.(3 marks) Explain the roles of the respiratory, excretory and circulatory systems of a mammal, and any connection between them.
Multiple Choice 1. Which of the following is NOT an essential feature of a gas exchange system? A. Close contact with the blood supply. B. Large surface area. C. Strong protective shielding. D. Moist membrane. 2. An animal’s respiratory system consists of a series of holes along the body which allow air to circulate into a network of tiny tubes throughout the tissues. This animal is probably a/an: A. insect. B. frog. C. fish. D. reptile.
7. (4 marks) One of the main features of any respiratory system is a large surface area for gas exchange. Outline how a large surface is achieved in a a) mammal
b) frog
3. A plant would probably show the lowest rate of transpiration under conditions of: A. hot & windy. B. bright light & low humidity. C. hot & bright light. D. high humidity & cool.
c) fish
d) insect
4. Which of the following correctly gives a structural feature and a functional feature of xylem tubes? A. living cells which transport water B. reinforced with lignin, carry out passive transport C. dead, hollow cells, carrying food nutrients D. cells filled with cytoplasm, carrying out active transport
8. (4 marks) Using simple schematic diagrams, contrast the circulatory systems of vertebrate and invertebrate animals. Answer on reverse. 9. (4 marks) a) Identify THREE structures in a plant which are involved in gas exchange.
Longer Response Questions Mark values given are suggestions only, and are to give you an idea of how detailed an answer is appropriate. Answer in the spaces provided.
b) Choose ONE of the structures listed in part (a) and describe one feature of it which aids gas exchange in the plant.
5. (6 marks) Contrast the processes of Transpiration and Translocation in a plant, including a) the substances transported
10. (4 marks) Outline the way in which technology, such as radio-isotope “tracing” is used to study the path of elements through a living plant or animal.
b) the plant tissues involved
c) the basic mechanism of transport involved.
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5. CELL DIVISION FOR GROWTH & REPAIR The Need For Cell Division
Mitosis Through the Microscope
Single-celled organisms reproduce by simply dividing in two.
You may have done a laboratory practical in which you used a microscope to examine a prepared slide of cells undergoing cell division. Commonly the root tip of a plant seedling is viewed. This sketch shows roughly what the cells may look like...
In a multicellular plant or animal cell division is vital for growth. Remember that individual cells cannot grow large because as they do, their SA/Vol ratio gets smaller, and they cannot get materials in and out through their cell membrane fast enough to survive. So, the only way to grow larger is to produce many small cells.
Most cells look like this one. No chromosomes visible, but DNA is being copied ready for mitosis to start.
Chromosomes just becoming visible. Mitosis is under way.
Cell division is also used to replace damaged or worn out cells in the body. For example, your body is constantly producing new blood cells to replace those that wear out.
The Process of Cell Division
Chromosomes have lined up in the middle of the cell.
Cell division occurs as a sequence of steps or “phases” as summarized by this schematic diagram.
THIS IS MITOSIS... THE DIVISION OF THE CELL NUCLEUS
Steps Original “parent” cell makes a copy of its genetic information
The chromosomes condense together and become visible. They line up in the middle of the cell, then separate into 2 identical groups
...more information
Chromosomes being pulled apart into 2 identical groups.
Genetic information is stored in the cell nucleus, as DNA. The DNA is contained in thread-llike “chromosomes” which are not normally visible.
These have just finished Cytokinesis.
The nuclear membrane dissolves so chromosomes can move right across the cell. They are moved by threads called “the spindle” which act like fishing lines, reeling them to opposite sides of the cell
These have just finished dividing the nucleus.
Chromosomes become visible after copying. Chromosomes lined up in middle of cell.
Once separated, each set of chromosomes forms a new nucleus
Finally, the cell membrane grows to divide the cell in 2 parts, with a share of cytoplasm and organelles in each
Chromosomes being pulled apart.
These 3 lower diagrams show how mitosis is often drawn in textbooks, in a stylized way. If you need to sketch them, do it like this for greater clarity
This final division is called “CYTOKINESIS”
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The Results of Cell Division
Mitosis in Other Organisms
• One parent cell divides to form 2 “daughter” cells.
A human baby is more or less the same shape as an adult, and simply grows bigger, proportionally all over, to become an adult. In other organisms though, cell division occurs only in certain parts of the body, and growth is not proportional.
• Each daughter cell is genetically identical to the other, and to the parent cell. This is because the original DNA was first duplicated (“replicated”) then divided into twoduplicate sets by mitosis. • The daughter cells are not necessarily identical in size, but each gets a share of cytoplasm, mitochondria, ribosomes and all other organelles.
Plants
• Each daughter cell can then make more organelles, and grow in size, until it is full size. Each may then undergo cell division again. This endless repetition of cell growth and cell division is called the “cell cycle”.
• at the root tip. • at the “buds” where shoots & flowers grow. • in the cambium layer, between xylem & phloem. (cambium growth is how the stem/trunk gets larger)
grow only at certain places “meristems”. These are located:
known
as
Insects
You began as a single cell. It divided by mitosis, then divided again and again, until today you are a complex organism of about 300 billion cells. Each of your cells is genetically identical to every other, and to that original cell you came from.
grow differently in two distinct stages. Most insects hatch from their egg as a “larva”... a caterpillar, grub or maggot. The larva does not undergo cell division at all, but grows rapidly by increasing the size of each cell. (within the limits imposed by the SA/Vol ratio, of course)
Even when you have finished growing, mitosis will continue in many parts of your body:
Next, the insect larva undergoes metamorphosis and totally changes its body plan. This is achieved by special “disks” of cells which begin mitosis in particular directions, each forming a different body part such as a wing, leg or vein. These “disks” correspond to the meristems of a plant, as special sites of mitosis.
• skin, to replace the layers that constantly flake off. • hair and finger-nails, which grow all your life. • bone marrow, where blood cells are constantly being produced to replace those that wear out. • anywhere else where injury or cell death requires replacement.
A Final Note... The main store of genetic material is the DNA in the nucleus, but that’s not the only place in a cell where DNA is found. DNA is also located in the mitochondria, and in chloroplasts in plant cells. These organelles are able to reproduce themselves (at least in part) in mini-versions of cell division.
Nuclear DNA
Chloroplast DNA
Mitochondrial DNA
This occurrence of DNA in these two important organelles (both concerned with food & energy, and its flow in ecosystems) will be dealt with in a later topic. The evidence points to a very interesting evolutionary origin for these organelles...
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Worksheet 10
Cell Division • Each group of chromosomes forms a new (j)........................................................ then cytokinesis divides the cell itself.
Fill in the blank spaces In a multicellular organism, cell division is necessary for (a).................................. and to replace damaged or worn out cells.
The results of cell division include that the daughter cells are genetically (k)......................................, and identical to the (l).......................... cell.
Mitosis refers to the division of the (b)............................., while the division of cytoplasm into 2 cells is called (c)............................................................
Apart from the nucleus, 2 other organelles contain DNA. These are the (m).......................... and .....................................
Before mitosis becomes visible in a cell the genetic information (d).............................. ...........
Sites of mitosis in a plant are called “(n)................... located at (o)........................, and (p)................................ as well as the cambium layer in the stem.
The genetic information is contained in the chemical (e).................... which is built into thread-like structures called (f).............................
Most insects hatch from their egg as a q)................. which grows by cell r)......................, without cell s).............................. Later, they undergo t)......................................... in which their body tissues totally u).......................................... and are re-built to form the totally different adult. During this process, cell division occurs only in special “v).........................................” of cells.
The visible sequence of mitosis is: • chromosomes thicken, become visible, and the nuclear membrane (g).................... • chromosomes (h).................................... in the middle of the cell • chromosomes move to opposite ends of the cell, pulled by the threads of the (i)............................................
Worksheet 11
Practice Questions (Section 5) Longer Response Questions
Multiple Choice
Mark values given are suggestions only, and are to give you an idea of how detailed an answer is appropriate. Answer in the spaces provided.
1. The sketch shows some plant cells which are undergoing cell division.
2. (6 marks) Describe the sequence of steps that occur in the processes of mitosis & cytokinesis.
The correct sequence of cell division is shown by the cells A. SPQTR B. RSPTQ P C. RQPTS D. PQTSR Q
3. (4 marks) a) Identify the parts of a plant where cell division occurs.
R
T
S
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b) Contrast the general pattern of growth of a plant with that of a vertebrate animal such as a mammal.
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CONCEPT DIAGRAM (“Mind Map”) OF TOPIC Some students find that memorising the OUTLINE of a topic helps them learn and remember the concepts and important facts. Practise on this blank version.
PATTERNS in NATURE
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11. Organic chemicals are mainly complex molecules, often polymers, based on the element carbon. e.g. carbohydrates, proteins, lipids & nucleic acids. Inorganic chemicals in living cells are small, simple molecules or mineral ions e.g. water, oxygen, nitrate & chloride ions.
Answer Section Worksheet 1
Cell Structure
a) all living things.... b) ...pre-existing cells c) microscopes d) resolution e) electron f) magnification g) Robert Hooke h) cytoplasm i) nucleus j) chloroplast k) cell wall l) cell membrane m) vacuole n) cell wall & (o) chloroplast (p)-(t) (any order) golgi body, endoplasmic reticulum, mitochondria, ribosomes, lysosomes (u) controls substances going in/out of cell v) Endoplasmic reticulum w) packaging substances for storage or secretion x) mitochondria y) chloroplast z) strength/ rigidity/ protection on outside of plant cell
Worksheet 2
12. Semi-permeable means that some chemicals can diffuse through it easily, while others cannot get through . 13. Diffusion is the movement of any solute, solvent or gas along the concentration gradient. Osmosis is the diffusion of WATER, against the concentration gradient, through a semipermeable membrane. 14. As any object gets larger, its SA/Vol ratio gets smaller. A cell needs nutrients, oxygen, etc in proportion to its volume, but must get these substances in through its cell membrane, the size of which is its surface area.
Chem & Membrane
a) inorganic b) carbon c) proteins d) membrane e) energy storage compoundsf) carbohydrates g) C6H12O6 h) photosynthesis i) cellular respiration j) DNA k) sugar (glucose) l) Biuret reagent m)yellow/brown n) black/dark blue o) phospholipid p) permeable q) high(er) r) lower s) water t) gradient u) passive v) energy or ATP w) Surface area / Volume x) volume y) cell membrane z) surface area aa) many ab) large
Therefore, a large cell (with a smaller SA/Vol ratio) would not be able to take in necessary substances fast enough to survive.
Worksheet 4
Worksheet 3 1. C 2. A 3. B 4. D 5. D 6. B 7. B 8. A 9. The light ‘scope forms images by focusing light beams with glass lenses. Electron ‘scopes focus beams of electrons using magnetic fields. Light scopes achieve magnifications around 500X and resolution of about 0.2 um. Electron scopes are 500-1,000 times better in each department.
Worksheet 5
Animal Nutrition
a) enzymes b) sugars c) amino acids d) salivary glands, stomach, pancreas & small intestine e) surface area f) small intestine g) liver h) large & flat i) long j) bacteria k) cellulose l) sharp, tearing m) short n) hummingbirds o) short & simple
10. Nucleus- membrane has pores to allow RNA messengers to go out into the cell. OR Mitochondrion- inner membrane is highly folded for more surface area. The enzymes of cellular respiration are arranged on these membranes for greater efficiency.
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Plant Nutrition
a) Autotrophs b) heterotrophs c) carbon dioxide d) water e) glucose f) oxygen g) chloroplasts h) chlorophyll i) light j) glucose k) polymerization l) starch m) cell walls n) lipids o) minerals (inorganic ions) p) proteins q) root hairs r) surface area s) osmosis t) xylem u) light absorption v) palisade w) circulation of water & gases throughout the leaf x) stomates y) transpiration z) carbon dioxide
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Worksheet 6
Worksheet 7
1. B 2. B 3. A 4. D 5. D 6. B 7. C
a) surface area c) blood supply e) trachea g) bronchioles i) simple/ less S.A. k) spiracles m) SA/Vol o) filaments q) counters) heart
8.Autotrophs are organisms that can make their own food. example: Plants Heterotrophs have to eat food made by other organisms. example: animals. 9. light energy a) Carbon dioxide + water
Glucose+ Oxygen
b) 1. It makes all the food, and is the basis of all the food chains 2. It makes all the oxygen in the atmosphere.
Worksheet 8
Plants
a) stomates b) lenticels c) root hairs d) water & minerals e) roots f) leaves g) transpiration h)& i) temperature/wind/humidity/light j) phloem k)translocation l) the plant must expend energy m) passive
10. a) Although glucose is the immediate product of photosynthesis, it is rapidly polymerised to form starch. Therefore, starch is found in large quantities in a photosynthesising leaf, but very little glucose could be detected. b) First the leaf is boiled, then washed in hot alcohol to decolourise it, so colour tests can be seen. Then it can be soaked in iodine solution to test for starch. A black colour indicates the presence of starch.
Worksheet 9 1. C 2. A 3. D 4. B 5. a) b) c)
11. Palisade layer: composed of cells neatly and tightly packed together under the upper epidermis where there is maximum light. Each cell is packed with chloroplasts. These features all help the palisade layer carry out maximum photosynthesis.
Transpiration water xylem passive
Translocation food nutrients (sugar) phloem active
6. Respiratory system: carries out gas exchange. Excretory system: removal of wastes. Circulatory system: transports substances around the body, including gases and wastes... therefore connects with respiratory and excretory systems.
Spongy layer: composed of cells that are very loosely packed. This allows spaces for water & gases to more easily diffuse to/from stomates & veins and so helps supply photosynthesising cells.
7. a) Mammal’s lungs have millions of tiny air sacs (alveoli). b) Frog has very simple lungs, but increases respiratory surface by using skin, mouth and throat membranes for gas exchange as well. c) Fish’s gills are made up of thousands of leafshaped filaments. Each is flat & thin, giving large contact area with water flowing past. d) Insects have microscopic, branched air tubes (trachea) that penetrate throughout their body. This gives a large area of contact with air for gas exchange.
12. Grazing herbivores need very long intestines & large caecum, so food has more time in the gut while mutualistic bacteria digest the cellulose. Meat-eating carnivores do not need such long intestines because meat is easier to digest and more nutritious. They have shorter intestines but a stomach that can take in a large meal, less often, and digest the high protein meat. Nectar feeders (e.g. honey-eater birds) eat a diet high in sugar which needs no digesting at all. They have very simple, short systems since they only need to absorb the sugar into their bloodstream.
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Animals b) moist d) diffusion f) bronchi h) alveoli j) skin & mouth/throat cavity l) trachea n) gills p) in opposite direction r) closed t) invertebrate
8. The main thing is to show that vertebrates have a “closed” system (blood is always inside a blood vessel) while many invertebrates have “open” systems, where the blood leaves blood vessels and “bathes” the cells at some part of the circulation.
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Worksheet 9 (cont)
Worksheet 11
9. a) stomates, lenticels & root hairs b) Root hairs: these microscopic outgrowths from root cells increase the surface area available. This helps gas exchange (as well as water absorption).
1. C 2. • Genetic information (DNA) is replicated. • Chromosomes become visible in the nucleus. Nuclear membrane dissolves. • Chromosomes line up in centre of cell. Spindle forms. • Chromosomes pulled apart into 2 identical groups. • Each group forms a new, identical nucleus. • Cytokinesis now divides the cytoplasm & organelles into 2 separate cells.
10. Chemicals containing radio-active “tracers” are introduced into living things, and any movement is tracked by detecting the radiation produced by the radio-isotope. For example, CO2 gas, containing radio-active carbon-14, is absorbed by a plant leaf, converted to sugar and transported to storage in the roots. This movement can be studied and tracked by the radiations from the carbon-14.
Worksheet 10
3. a) “Meristems” located at root tips, buds and cambium. b) Plants grow only at the meristems, and usually grow dis-proportionally in different parts of their body. This means they may drastically change their shape & proportions as they grow. In contrast, mammals grow fairly evenly in every body part and stay more or less in proportion all their life.
Cell Division
a) growth b) nucleus c) cytokinesis d) is copied/duplicated/replicated e) DNA f) chromosomes g) dissolves h) line up i) spindle j) nucleus k) identical l) parent m) mitochondria & chloroplast n) meristems o) root tips p) shoot tips (buds) q) larva r) enlargement s) division t) metamorphosis u) break down / change v) disks
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