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Higher Biology

Units 1,2 and 3

What is a Unicellular organism? An organism which consists of only one cell. This single celled organism must be able to perform every life function in one cell.
What is a multicellular organism? An organism which consists of more than one cell. Cells in multicellular organisms are specialised for a single function and rely on a variety of cells in other tissues to perform all the other life functions- this is known as "division of labour".
Give two examples of specialised cells. 1. Sperm cells are specialised for swimming so their structure includes a tail for propulsion and lots of mitochondria to supply energy. 2. Palisade mesophyll cells contain many chloroplasts to absorb maximum light energy for photosynthesis.
What is meant when the cell membrane is described as "selectively permeable"? This means that molecules of different substances diffuse through the membrane at different rates-and many cannot diffuse through at all. Smaller molecules can diffuse through rapidly, whereas larger molecules either take more time or cannot pass.
What does the term "High water concentration" mean? A high proportion of water and very little solute. Pure water has the highest water concentration possible.
What does the term "low water concentration" mean? A solution with lots of solute dissolved in it.
What is osmosis? The movement of water molecules through a selectively permeable membrane from a region of high water concentration to a region of low water concentration.
What does the term "Hypotonic" mean? -a less concentrated solution (and therefore one with a higher water concentration) than the other solution it is being compared with.
What does the term "Hypertonic" mean? -A more concentrated solution (and therefore one with a lower water concentration) than the other solution it is being compared with.
What does the term "Isotonic" mean? - a solution with the same solute/water concentration as the other solution it is being compared with.
What happens when animals are immersed in: a) Hypotonic solutions b) Hypertonic solutions? a)They burst because they have no cell wall. b)They shrink.
What happens when plant cells are immersed in: a) Hypotonic solutions b) Hypertonic solutions? a)They become turgid. b)They become plasmolysed.
How do cell walls help prevent plant cells from becoming damaged in different solutions? Cellulose walls are rigid and therefore keep plant cells in more or less the same shape and prevent them from bursting when water enters the cell via osmosis, or from shrinking very much when water leaves the cell.
How does the structure of the cell wall make it suited to its function? -Cell walls are completely permeable and so present little obstacle to diffusion. -Cell walls are made of cellulose fibres in criss-cross layers which gives support but allows permeability (like a basket).
What is cellulose? Cellulose is a large structural carbohydrate molecule.
Describe the structure of the cell membrane/plasma membrane. - described as a "fluid mosaic". - has a bi-layer of phospholipids with embedded protein molecules. -Some of these proteins have channels that can transport some substances rapidly through the membrane, but can prevent other substances from entering.
How does the structure of the cell membrane/plasma membrane make it suited to its function? Its structure makes the membrane both selectively permeable and very fluid- it can change shape very easily and quickly.
What are the 5 ways in which substances can move in and out of cells? Diffusion, osmosis, active transport, endocytosis and exocytosis.
What is diffusion? The movement of a substance down a concentration gradient from a region of a high concentration to a region of a low concentration.
What is active transport? The movement of a substance against a concentration gradient from a region of low concentration to a region of high concentration. This requires energy and is a selective process as individual ions and molecules are accumulated or expelled.
Identify whether the 5 ways in which substances can move in and out of cells are active or passive processes. -Active- active transport, endocytosis and exocytosis. -Passive- diffusion, osmosis.
What are the limiting factors of active transport? - anything that reduces the shortage of ATP. E.g. shortage of food or oxygen, temperatures being higher or lower than the optimum and chemicals that inhibit respiration.
What are the 3 fates of light falling on a leaf? It can be absorbed, transmitted or reflected.
What does it mean when light falling on a leaf is transmitted? It passes right through the leaf.
What does it mean when light falling on a leaf is reflected? It bounces off the surface of the leaf.
What does it mean when light falling on a leaf is absorbed? It is converted to heat energy by the plant as only some of the light absorbed can be used for photosynthesis.
What is the range of colours in white light referred to as? A spectrum.
What are photosynthetic pigments? Special molecules which absorb light.
What is the main photosynthetic pigment in a plant? Chlorophyll. There are two forms of chlorophyll: chlorophyll A and chlorophyll B.
What are Carotene and Xanthophyll examples of? Accessory pigments.
Name the four main photosynthetic pigments in plants in order of their arrangement on a piece of chromatography paper (lowest to highest). Chlorophyll B, chlorophyll A, xanthophyll, Carotene.
What is the action spectrum? A graph which shows the rate of photosynthesis by a green plant at different wavelengths of light.
What are the colours of the 4 main photosynthetic pigments? -Chlorophyll B= green -Chlorophyll A= blue/green -Xanthophyll= yellow -Carotene= yellow
What is the absorption spectrum? A graph showing the quantity of light absorbed by a pigment at different wavelengths.
What are the main wavelengths of light absorbed by leaves for photosynthesis and which is the least absorbed wavelength? -Blue and red. -Least absorbed= green. This gives leaves their green appearance.
What happens to the blue and red wavelengths of light which are absorbed by chlorophyll A and chlorophyll B? They are converted to chemical energy which is then used to regenerate ATP and to split water.
What do the accessory pigments do? The absorb wavelengths other than blue and red and pass on the absorbed energy to chlorophyll.
What is chromatography? A technique which is used to separate the components of a mixture that differ in their degree of solubility.
Describe the process of chromatography. -Leaf tissue ground with acetone to dissolve pigments. - Filtering separates cell debris from clear pigment solution. -Concentrated spot of pigment built up near bottom of paper. -Pigments separated as chromatography solvent moves through paper.
What is the chromatography solvent made from? Acetone or petroleum ether.
What happens to the pigment which dissolves the best in chromatography? It rises highest on the chromatography paper.
How can the Rf value for each pigment be calculated? Distance moved by the pigment divided by the distance moved by the solvent front.
What are chloroplasts? Green disk shaped organelles enclosed in a double membrane. This structure is responsible for photosynthesis in a plant cell.
What are the grana? stacks of discs containing photosynthetic pigments. The site of the light dependent stage of photosynthesis.
What are the lamellae? A network of membranes joining the grana together. These keep the grana in best position for maximum light absorption.
What is the stroma? The enzyme rich fluid which fills the rest of the chloroplast and is the site of the Calvin cycle.
What is photolysis? The breakdown of water during the light dependent stage of photosynthesis to produce oxygen and hydrogen.
What happens to the hydrogen produced in the light dependent stage of photosynthesis? It combines with the hydrogen carrier NADP, which becomes NADPH2 and is used in the Calvin cycle.
What happens to the oxygen produced in the light dependent stage of photosynthesis? It is released into the atmosphere as a by-product.
What happens to the ATP which is synthesised in the light dependent stage of photosynthesis? It is used to supply energy for carbon fixation in the Calvin cycle.
What is meant by energy transfer? The role played by ATP between energy releasing and energy consuming reactions.
What is phosphorylation? The process by which ATP is regenerated by ADP and Pi. This is a reversible reaction.
What is ADP? A low energy molecule composed of adenosine and 2 phosphate groups.
What is Pi? An inorganic phosphate group needed to make ATP
What is ATP? Adenosine tri-phosphate. A high energy molecule composed of adenosine and 3 phosphates.
What is the Calvin Cycle? A sequence of enzyme controlled reactions that produce glucose by the reduction of carbon dioxide. It requires ATP from the light dependent stage, hydrogen from the photolysis of water and carbon dioxide from the atmosphere.
In the Calvin cycle what happens to carbon dioxide? It combines with 5-carbon RuBP to form an unstable 6-carbon compound.
What happens to the unstable compound formed in the Calvin cycle when Carbon dioxide combines with RuBP? The unstable 6-carbon compound breaks down to give 2 molecules of the 3-carbon GP (Glycerate Phosphate).
What happens to GP in the Calvin cycle? Some of the GP is converted to 6-carbon glucose, the rest is used to regenerate RuBP. This requires both hydrogen and the energy from ATP which come from the light dependent stage.
What happens to the glucose formed in the Calvin cycle? It may be converted to starch for storage or cellulose.
What is respiration? A biochemical pathway (aerobic or anaerobic) which involves the synthesis of ATP using the energy from glucose. The 3 stages of respiration are glycolysis, Krebs cycle and cytochrome system. All of these stages are controlled by enzymes.
Where does Glycolysis take place? In the cytoplasm.
Describe the process of Glycolysis. - 6-carbon glucose is split into 2 molecules of 3-carbon pyruvic acid. - Hydrogen is released which is accepted by NAD which becomes NADH2. -Oxygen is not required for glycolysis.
What is the substrate for Glycolysis? Mainly glucose, but fats and proteins can also be used.
a) How many ATPs are needed to start glycolysis? b) How many ATPs are produced by glycolysis? c) What is the overall net gain of glycolysis? a)2 b)4 c)2 per glucose molecule
Where does the Krebs cycle take place? In the central matrix of the mitochondria.
Describe the process of the Krebs cycle. - pyruvic acid converts to 2-C acetyl group and CO2 is released - acetyl group combines with coenzyme A to give acetyl CoA - acetyl CoA combines with 4C compound to give citric acid -Citric acid converts to 5C and then 4C compound + reacts with acetylC
What happens to hydrogen and carbon in the Krebs cycle? -each time carbon is lost it is released as carbon dioxide -Hydrogen is also released at this time and collected by NAD to form NADH2
Why is oxygen needed in the Krebs cycle? This is an aerobic phase of respiration. Oxygen is necessary because the hydrogens which are released cannot pass through the system unless oxygen is present to act as the final acceptor of the hydrogens.
Where does the cytochrome system take place? On the cristae of the mitochondrion.
Describe the process of the cytochrome system. -Hydrogen from earlier stages taken as NADH2 to the cytochrome system -It is passed through a series of carriers -at each step enough energy is released to synthesise one ATP from ADP and Pi. -Oxygen is the final H2 acceptor. Water produced.
What is a mitochondrion? A cell organelle bounded by 2 membranes. The inner of these 2 membranes is folded to form a greatly increased surface area. These folds are called cristae. This organelle is the site of respiration in cells. Also has fluid filled central matrix.
How many ATPs are formed by: a) aerobic respiration b) anaerobic respiration? a)38 ATP b) 2 ATP
What happens after glycolysis when respiration is anaerobic? The pyruvic acid is converted to lactic acid in humans and ethanol and carbon dioxide in plants.
What are proteins made from? Chains of amino acids, of which there are 20.
What do the structure and properties of different proteins depend on? The length of the amino acid chain and the order in which the amino acids form the chain.
What are the two types of protein? Fibrous or globular.
What are fibrous proteins? Insoluble structural proteins from which many body tissues such as bone, ligament, muscle and hair are made. E.g. Collagen.
What are globular proteins? Not truly soluble, but form suspensions in water and can have a variety of functions, e.g. as enzymes, membrane proteins, some hormones and antibodies.
What are chromosomes made of? DNA which is curled into the double helix shape.
What are the basic units of DNA? Nucleotides.
What do nucleotides consist of? A deoxyribose sugar, a phosphate and one of the four nitrogenous bases.
Name the four nitrogenous bases found in DNA and state which bases link to each other. Adenine-thymine Guanine-cytosine
Describe the process by which DNA molecules replicate. -Molecules uncoil and unzip to expose bases -Free DNA nucleotides join to the exposed bases -adjacent nucleotides join to form sugar-phosphate backbone
What does DNA replication require? -Supply of enzymes -Supply of free nucleotides -energy in the form of ATP -original DNA to act as template
What does DNA replication produce? 2 identical DNA molecules.
When does DNA replication occur? Before every cell division.
Why is DNA replication important? Every cell which is produced by an organism must receive a full set of instructions if it is to function properly.
What does DNA stand for? Deoxyribonucleic acid.
What does RNA stand for? Ribonucleic acid.
Name the 3 differences between DNA and RNA. -DNA is double stranded, whereas RNA is single stranded -DNA contains thymine, whereas RNA contains uracil instead -DNA contains the sugar deoxyribose, whereas RNA contains the sugar ribose instead
What is mRNA? Messenger RNA
Where is mRNA formed and what is the formation of mRNA known as? In the nucleus using the DNA template for a particular gene. This is called transcription.
What is a gene? A short length of DNA which codes for a particular protein.
Describe the process of transcription. -a short length of DNA (a gene) uncoils and unzips at the correct part of the chromosome -free RNA nucleotides bond to the exposed bases on one DNA strand -adjacent RNA nucleotides join to form sugar-phosphate backbone -mRNA molecule peels off
What happens after mRNA has peeled off of the original DNA strand? The DNA zips up again and the mRNA molecule then moves out of the nucleus to attach to a ribosome for protein synthesis.
What is protein synthesis on the ribosome also known as? mRNA translation.
What is a codon and what does this code for? -a triplet of bases on mRNA -codes for only one specific amino acid
What is an anti-codon? a triplet of bases on tRNA
What does tRNA stand for? Transfer RNA
What does tRNA do? It captures a specific amino acid in the cytoplasm and brings it to the ribosome.
How are amino acids lined up in order? Each mRNA codon in a ribosome attracts a molecule of tRNA with a corresponding anti-codon. The amino acids are attached to their neighbour by peptide bonds and so the protein builds up.
What type of bond exists between amino acids? A peptide bond.
How is the order of amino acids in a protein determined? By the sequence of bases in the DNA which are transcribed into the sequence of bases in the mRNA codons.
What are ribosomes? Tiny structures which are attached to the rough endoplasmic reticulum. They are the site of protein synthesis where the sequence of mRNA triplet codes are translated into proteins.
What is the rough endoplasmic reticulum? A continuous network of membranes throughout a cell which functions as a transport system for proteins.
What happens to proteins at the Golgi apparatus? they are processed or "packaged" for secretion. The Golgi apparatus attaches various carbohydrates to the proteins, making them glycoproteins
What happens after proteins are packaged and processed by the Golgi apparatus? Vesicles pinch off the ends of the Golgi body and carry the proteins to the plasma membrane for secretion.
What are viruses and what do they consist of? Extremely small micro-organisms which exhibit living and non-living characteristics. They consist of a strand of DNA surrounded by a protein coat called a caspid.
Describe the process by which viruses replicate. -They invade cells and take over their metabolism and so the cell replicates the virus DNA -The cell is then made to synthesis viral protein coats and the new virus particles are assembled -These are then released when the host cell bursts (lysis).
What are the main mechanisms of cellular defence in animals? Phagocytosis and antibody production.
What is phagocytosis? The process by which specialised white blood cells called phagocytes engulf and destroy invading viruses or foreign bacteria.
Describe the process of phagocytosis. The foreign material is enclosed in a vacuole and lysosomes merge with the vacuole and release powerful digestive enzymes which destroy the material. This is a non-specific process.
What are lysosomes? Cell organelles which contain powerful digestive enzymes.
What are antibodies? Specific Y-shaped proteins which attack invading organisms. They are made by lymphocytes.
What are lymphocytes? White blood cells which defend the body from foreign antigens.
How do lymphocytes recognise foreign invaders? By the antigens they carry on their surfaces.
What are antigens? Complex compounds, usually a protein, which stimulates an antibody response.
What do lymphocytes do when they recognise a foreign invader? They produce the particular antibody required to combat that particular antigen. Each antibody is specific to one antigen.
How do antibodies combat foreign invaders? They attach themselves to the invader, rendering them harmless and attract phagocytes to dispose of them. After each attack, a few of the lymphocytes remain as memory cells so that that particular invader can be easily disposed of in the future.
Why do a lot of organ transplants not work? Because transplanted organs (e.g. kidney) also have antigens that are recognised a foreign by lymphocytes and antibodies attempt to attack them. This is known as tissue rejection.
How can doctors reduce the chance of tissue rejection? By matching the antigens of the donor and the recipient as closely as possible and by using drugs to supress the immune system (however this leaves the patient vulnerable to viruses, diseases etc.).
What are the two main ways of cellular defence in plants? The production of poisonous chemicals and the isolation of injured areas to prevent the spread of infection.
Give three examples of poisonous chemicals produced by plants as way of defence. -tannins -cyanide -nicotine
How can the spread of infection be prevented in plants? By isolating the injured area by means of sticky substances such as resin.
Why is sexual reproduction important? Sexual reproduction is vital in enabling the genetic variation of populations to be maintained. Since natural selection acts upon this variation, sexual reproduction is very important for evolution.
What does sexual reproduction involve? The fusion of two haploid gametes. This is called fertilisation.
What is meant by meiosis? The process by which gametes are formed. It involves 2 cell divisions producing 4 haploid gametes from 1 diploid gamete mother cell.
What is meant when gametes are described as haploid? Each gamete contains only one set of chromosomes.
Where does meiosis take place? In animals meiosis takes place in the ovaries and testis. In plants meiosis takes place in the ovaries and anthers.
Describe the process of the first meiotic division. -Chromosomes replicate making 2 chromatids at centromere -Chromosomes shorten + thicken -Homologous chromosomes connect, forming 4 stranded bivalents -These line up at equator + attach to spindle fibres -They are torn apart to poles + cell divides in
Describe the process of the second meiotic division. -Each chromosome lines up at equator of cell -Spindle fibres attach each centromere to opposite poles of cell -Spindle fibres drag chromatids to opposite poles of cell -Each cell divides, so now there are 4 gametes, each with 1 set of chromosomes
What is the main source of variation in gametes? Main source of variation in gametes results from lining up of chromosomes at the equator of the cell during the 1st meiotic division. Since the chromosomes line up randomly each gamete receives a random assortment of maternal and paternal chromosomes.
What is independent assortment? The random positioning of chromosome pairs during the 1st meiotic division. This ensures that each offspring receives a new phenotype.
What is a dihybrid cross? A dihybrid cross is when we consider the inheritance of 2 genes at the same time.
What is the expected ratios from the following crosses: a) AaBb X AaBb b) AaBb X aabb c) Aabb X aaBb a) 9:3:3:1 b) 1:1:1:1 c) 1:1:1:1
What are linked genes? Genes on the same chromosome.
How can linked genes be separated? The only way linked genes can be separated is if chiasmata occurs.
What is chiasmata/crossing over? Points of attachment between homologous chromatids at the 1st stage of meiosis.
What effect does linked genes have on the number of gametes present in a cross? Cuts down the maximum possible number of gametes from 4 to 2. The result is that we get far more than the predicted number of the 2 parental types and none of the others.
What are recombinant gametes? The gametes formed as a result of chiasmata taking place. The recombinant offspring will have a different combination of alleles for a particular gene than the parents and so may have a different phenotype.
How is the frequency of recombinants affected by linked genes? The frequency of recombinants between any 2 linked genes increases the further apart the genes are on the chromosome and so the percentage of recombinant phenotypes gives us a way of measuring the spacing of genes on a chromosome.
How is the frequency of chiasmata affected by the spacing of linked genes on a chromosome? The frequency of crossovers between any 2 linked genes increases the further apart the genes are on the chromosome.
How does chiasmata affect linked genes? When a crossover happens, 2 genes which had previously been linked become independent of each other. This is a source of variation , as it gives new combinations of alleles.
Which chromosomes determine the sex of animals? The X and Y chromosomes.
What is meant by sex linked genes? Genes which can be found on the X chromosome but not on the Y chromosome.
Sex linked conditions are mostly found in which gender? Why is this so? Males. Because a male child inherits the recessive allele for a sex linked condition from his mother.
What are mutations? Spontaneous changes in the genotype of a cell. They are completely random and relatively rare. They give rise to new alleles which did not exist before and are a major source of variation in populations.
How can the rate of mutation be affected? The rate of mutation can be increased by exposure to mutagenic agents.
What are mutagenic agents? Things which increase the rate of mutation. These include chemical agents, irradiation (X-rays and UV light) and extreme heat.
What are the 2 main types of mutation? Chromosome mutations and gene mutations.
What are chromosome mutations? Changes in the number of chromosomes or in the structure of an individual chromosome involving more than one gene.
What are changes in chromosome number caused by? non-disjunction during meiosis due to spindle fibre failure.
What is the result of only one chromosome being affected by non-disjunction in humans? The offspring may have an extra chromosome (Downs' Syndrome or turner's syndrome) or one chromosome missing.
What is the result of all the chromosomes being affected by non-disjunction in humans? The gametes are produced with complete extra sets of chromosomes or no chromosomes at all (non-viable).
What is the result when gametes with double sets of chromosomes are fertilised? Polyploid individuals.
What is polyploidy? Having more than the diploid number of chromosome sets.
What are Polyploid plants? Plants which have one or more sets of chromosomes in excess to the normal diploid number.
What is the result of polyploidy in plants? Increased vigour which can give advantages in crop production such as increased yield, hardiness and resistance to disease.
When do chromosome mutations occur? When parts of a chromosome become separated and reattached.
What are the 4 types of mutations in chromosome structure? -deletion -duplication -translocation -inversion
What is deletion as a chromosome mutation? This is where one or more genes have been lost from a chromosome.
What is duplication? This is when a chromosome has 2 copies of a gene or genes- 1 copy coming from the homologous chromosome.
What is translocation? This is when a chromosome has 2 copies of a gene or genes- 1 copy coming from a non-homologous chromosome.
What is inversion? When 2 or more genes come out, flip about and are reinserted into the same chromosome.
What are gene mutations? Altercations in the sequences of bases of DNA.
What are the 4 types of mutations in genes? -substitution -insertion -deletion -inversion
What is the result of changes in the DNA sequence? Changes in the sequence of amino acids in the protein being coded for and so its shape. Substitution or inversion may only alter a single amino acid. Insertion and deletion change all the triplets after the mutation point and so all the amino acids.
What is natural selection? The survival of the fittest (those organisms best suited to their environment).
What is a species? A group of organisms which are sufficiently closely related to breed with each other and produce fertile offspring. They share a common gene pool.
What are isolating mechanisms? Barriers to genetic exchange- this can lead to the evolution of a new species.
Name the 3 types of isolating barriers. Geographic, ecological or reproductive.
Give examples of geographical barriers. Rivers, mountains, canyons, oceans and any other geographical feature that separates two regions.
Give examples of ecological barriers. Although groups are not geographically isolated from each other they may be isolated by such things as occupying different habitats or breeding areas, pH, salinity.
Give examples of reproductive barriers. Breeding between groups within a population may not be possible because of differences in courtship behaviour, physical differences which prevent mating, or failure of gametes to fuse.
Explain how an isolating barrier can lead to the evolution of a new species. -When a species becomes divided into 2 populations by an isolation barrier there is no interbreeding or exchange of genes between the groups -The environment for both groups may differ Both mutations and natural selection will differ + change each group.
How can it be determined that one species has become 2 due to isolating barriers? Once the 2 groups can no longer interbreed and produce fertile offspring, they have become 2 separate species.
What is adaptive radiation? The evolution of several different species from a common ancestor.
Give 2 examples of high speed evolution. -The evolution of antibiotic resistant strains of bacteria -Changes in gene frequency of the melanic form of the peppered moth
What can be done by man to preserve species and maintain genetic diversity? -wildlife reserves -captive breeding -cell and seed banks -laws an quotas
How have humans contributed to the evolution of both crop plants and domesticated animals? Through selective breeding.
What is selective breeding? The selection of particular animals or plants which possess a desired characteristic to breed in order for the offspring to inherit this characteristic.
Describe the selective breeding process. -Parents selected for desirable characteristics -offspring that have this characteristic are bred again -offspring which do not possess the wanted trait are prevented from breeding -desirable trait becomes common over long period of time. -
What is hybridisation? -Another artificial technique for producing new types of plants and animals -It involves the crossing of 2 breeds or varieties of the same species -The offspring are heterozygous for many alleles which gives hybrid vigour
What is genetic engineering? The artificial transfer of genes from one organism to another.
Why is genetic engineering useful to humans? Techniques of genetic engineering have greatly increased the ability of humans to produce new varieties by allowing direct manipulation of genes.
Describe the process of genetic engineering. -Desired gene located -Gene cut out -Plasmids removed from bacteria -Gene sealed into plasmid -Plasmid and bacteria mixed and plasmid is taken up again -Bacteria multiply and produce product
How is a gene located in genetic engineering? Through use of a gene probe or by recognising characteristic bonding patterns on chromosome.
What is used to cut the desired gene out in genetic engineering? restriction endonuclease enzyme.
How are plasmids removed from bacteria in genetic engineering? Using restriction endonuclease enzyme.
How is the desired gene sealed into the plasmids in genetic engineering? Using ligase enzymes.
Give to examples of products produced from genetic engineering. Human insulin and human growth hormone using E. Coli.
What is somatic fusion? The fusion of ordinary plant cells (not gametes)in genetic engineering.
What is the advantage of somatic fusion? Crosses can be achieved between 2 plant species which could not normally interbreed.
Describe the process of somatic fusion. -Cell walls removed to give protoplasts -protoplasts from 2 species fused -Resulting cells are grown into plants -New plant has characteristics from both species.
How are the cell walls removed in somatic fusion? Using the enzyme cellulase.
Give an example of an application of somatic fusion. The introduction of disease resistance from a wild potato plant into a high yielding crop plant.
Freshwater fish are what to their environment? What effect does this have on them? Hypertonic. They gain large volumes of water by osmosis through their gills and mouth lining, and lose salts through diffusion.
How have freshwater fish adapted to survive in their environment? -They have large kidneys with many glomeruli which filter water out the blood rapidly -They have short kidney tubules -They produce large volumes of dilute urine -chloride secretory cells in gills take in salts by active transport
Saltwater (marine) fish are what too their environment? What effect does this have on them? Hypotonic. They lose large volumes of water by osmosis and gain salts by diffusion.
How have saltwater fish become adapted to survive in their environment? -They constantly drink the surrounding water -Chloride secretory cells in the gills expel salts by active transport -Kidneys contain very few, small glomeruli (or none)so blood is filtered very slowly -produce small volume of urine (isotonic to blood)
Describe and the adaptations of salmon and eels. Both fish migrate over long distances and spend part of their lives in freshwater and the rest at sea. They can have the osmoregulation mechanisms of both the freshwater and saltwater fishes.
Explain how and why the kangaroo or desert rat has adapted to live in its environment. It lives in an environment where water is scarce and the days are extremely hot. These problems are solved by physiological and behavioural adaptations.
What are the physiological adaptations of the kangaroo/desert rat? -No sweat glands -Very long kidney tubules to reabsorb water and produce concentrated urine -maximum reabsorption of water in large intestine to produce dry faeces -narrow, cool nostrils which reduces water loss in exhaled air.
What are the behavioural adaptations of the Kangaroo/desert rat? -Nocturnal habit (feeds only during cooler night) -Remains in burrow (which is cooler, more humid) during day.
What is transpiration? The loss of water vapour from the leaves of plants
What is the transpiration stream? The flow of water through a plant from root hairs, through the cortex of the root into the xylem, until it is lost as vapour from the stomata in the leaves.
What does the transpiration stream do? -supplies water to all cells of the plant -allows the uptake of minerals -evaporation of water from leaves produces cooling effect
What are the factors which affect the rate of transpiration? -Temperature -Humidity -Wind Speed -Leaf surface area -Degree of stomatal opening
What are stomata needed for? -Gas exchange to allow photosynthesis
What are Xerophytes? Plants which are adapted to survive in very dry habitats.
What are Hydrophytes? Plants which are adapted to live in fresh water.
What is foraging? Food searching behaviour in animals.
Give 7 examples of foraging behaviours. -ants meander away from nest until food is found and leave scent trail -bees perform waggle dance to show direction of food -remaining where food is plentiful -eating whatever is available -finding hidden food -hunting weakest or best size of prey
What does survival depend on in terms of foraging behaviour? Survival depends on economical foraging in terms of optimum search patterns and selection of the best food.
What is inter-specific competition? Competition with between different species.
What is intra-specific competition? Competition between members of the same species.
Which is worse, inter or intra- specific competition and why? -intra-specific. -Because the animals have exactly the same needs and are competing for the same resources.
Give 3 examples of adaptations which ensure the best distribution of limited resources amongst a species? -dominance hierarchies -co-operative hunting in social groups -territorial behaviour
State 6 benefits of a dominance hierarchy. -reduced fighting over females -dominant animals gain most food/females -subordinate animals gain a share of food when plentiful -group shares sentry duty and warns others of danger -large group can defend females -large group can confuse/attack pre
State the 4 benefits of co-operative hunting. -being in a group increases an individual's chances of gaining food -group can take down larger prey than individuals -group will have more chance of success of catching prey -group can defend food/territory together
Under what circumstances will co-operative hunting occur? Group behaviour and food sharing will only occur as long as the reward for sharing exceeds that for individual foraging.
What is territorial behaviour? The protection of an area for sole usage by one or more animals.
What is meant when plants are described as sessile? They don't move around.
Name 3 things plants compete for? Water, light and soil nutrients.
What effect does grazing have on species diversity? It reduces it.
Why can grasses tolerate grazing? Because they have low meristems.
Why are broad leafed plants likely to be killed off completely by grazing? Because grazing removes all their apical meristems.
What is the compensation point? Light intensity at which rates of photosynthesis and respiration are the same.
What is habituation? Animal behaviour in which an animal temporarily ceases to respond to a harmless stimuli.
State 4 social methods of defence in animals? -extra lookouts -alarm calls -mobbing of predators -defensive formations
How are some plants able to tolerate grazing? -low meristems -deep root systems -underground stems
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