4 - Biodiversity, Evolution and Disease

Describe 3 adaptations of marram grass (xerophyte) and explain their importance

Leaf rolled longitudinally trapping air inside (air becomes humid and reduces water loss from the leaf); thick waxy cuticle on upper epidermis (reduces evaporation); stomata on lower epidermis inside rolled leaf (protected by enclosed air space); stomata are in pits in lower epidermis which is folded and covered by hairs (reduces air movement and hence water loss); spongy mesophyll very dense with few air spaces (less surface area for evaporation of water)

Cacti are succulents. What does this mean?

They store water in their stems which become fleshy and swollen

Why is it advantageous for some xerophytes to have a low water potential inside their leaf cells?

Reduces evaporation of water from the cell surfaces as the water potential gradient between the cells and the leaf air spaces is reduced

Describe two adaptations of roots that could help a plant survive in arid conditions

Roots could be very long to reach water deep in soil; roots could be very widespread to absorb water from a large area when it does rain.

What is classification?

The process of putting living things into groups

Why do scientists classify organisms?

It makes identification of organisms simpler. It predicts characteristics, comparing one species with others from the group. It identifies evolutionary links.

What is taxonomy?

A hierarchical grouping system, where each group is subdivided into smaller groups.

What are the eight taxonomic groups in order of largest to smallest?

Domain; Kingdom; Phyllum; Class; Order; Family; Genus; Species.

What is the binomial naming system?

A naming system devised by Karl Linnaeus. It uses two (bi) names. The genus and species. The genus has a capitalised first letter.

Why is the binomial naming system important?

A species may have many different common names, but the scientific name will be universal.

What are the 5 kingdoms in classification?

Prokaryotae, protoctista, fungi, plantae, animalia

What are the general features of prokaryotae?

- Unicellular
- No nucleus or membrane bound organelles
- A ring of naked DNA
- No feeding mechanism (nutrients absorbed or created through photosynthesis)

What are the general features of protoctista?

- Mainly unicellular
- Nucleus and membrane bound organelles
- Some have chloroplasts
- Some sessile, others have cilia or flagella or move through amoeboid mechanisms
- Nutrients aquired either by photosynthesis, ingesting of other organisms or both. Some are parasitic

What are the general features of fungi?

- Unicellular or multicellular
- A nucleus and membrane bound organelles
- A cell wall made of chitin
- No chloroplasts of chlorophyll
- No mechanisms for locomotion
- Body or mycelium made of threads or hyphae
- Saprotrophic (absorb nutrients mainly from decaying material) Some are parasitic
- Most store food as glycogen

What are the general features of plantae?

- Multicellular
- A nucleus and membrane bound organelles
- Cell wall made from cellulose
- All contain chlorophyll
- Do not move (some gametes have cilia or flagella)
- Autotrophic (nutrients created through photosynthesis)
- Store food as starch

What are the general features of animalia

- Multicellular
- A nucleus and membrane bound organelles
- No cell wall
- No chloroplasts
- Move using cilia, flagella or contractile proteins (sometimes in the form of muscular organs)
- Heterotrophic (nutrients aquired by ingestion)
- Store food as glycogen

What are the 3 domains of classification?

Bacteria, archaea, eukarya

Why are 3 domains preferred to 5 kingdoms?

1 Fits better with phylogeny
2 There are key differences between prokaryotes and the eucaryotes (other 4 kingdoms)
3 All of the 4 eucaryotic kingdoms have a nucleus
4 There are key differences between bacteria and archaea

What is the difference between eukarya, bacteria and archaea in terms of ribosomes?

Eukarya have 80s
Bacteria have 70s
Archaea have 70s

What is the difference between eukarya, bacteria and archaea in terms of RNA polymerase?

Eukarya have 12 proteins
Bacteria have between 8 and 10, very similar to eukaryotic ribosome
Archaea have 5 proteins

In the new system of classification, what are the 6 kingdoms?

Eubacteria, archaebacteria, protoctista, fungi, plantae, animalia

Which group has been divided to form eubacteria and archaebacteria?

Prokaryotae

What is the difference between the habitats of archaebacteria and eubacteria?

Archaebacteria - ancient bacteria, live in extreme conditions, such as hydrothermal vents or anaerobic conditions, they can make methane.
Eubacteria - true bacteria found in all environments, bust bacteria are in this kingdom.

What is phylogeny?

The name given to the evolutionary relationships between organisms.

What are phylogenetics?

The study of the evolutionary history of groups of organisms. How closesly related they are to one another.

What is a phylogenetic tree?

A diagram showing the evolutionary history of groups of organisms. They are branched, showing which groups have evolved from a common ancestor.

What are the advantages of phylogenetic classification over hierarchical / Linnean classification?

Phylogenetic classification conneects groups based on their relationships rather than thair characteristics; Phylogeny produces a continuum rather than discrete groups; Phylogony gives a better discription of the variety present within groups, rather than giving the impression all groups are equal in age and differentiation.

What is evolution?

The theory that describes how organisms change over many years through natural selection.

What did Darwin observe to support his thory of evolution through natural selection?

He realised that organisms best suited to the environment were more likely to survive and to reproduceand therefore pass on their characteristics to their offspring. Therefore a species over time will become more adapted to it's environment by having a more advantageous phenotype.

What did Darwin notice about the finches of the Galapagos?

He noticed that different islands had different finches, that although they were very similar, and therefore related, that their beaks and claws were different shapes and sizes.

What did Darwin determine about the shape of the Galapagos finchs' beaks and their environment?

He linked the shape of the finchs' beaks to the food that they ate. He concluded that the birds with beaks most suited to the available food would survive longer and be more likely to reproduce and pass on characteristics to their offspring.

Who was Alfred Wallace?

A contemporary of Darwin who independently developed a theory of evolution.

When Darwin published "On the Origin of Species" describing the theory of evolution through natural selection, why was it originally extremely controversial?

He read that fossils were evidence of animals from millions of years ago. He also read about the principle of uniformitarianism. That the Earth is shaped by processes still occuring today, erosion, weathering etc. This gave Darwin the idea that evolution was a very slow process.

What are the 3 main sources of evidence for evolution?

Paleontology; comparative anatomy; comparative biochemistry.

What is paleontology?

The study of fossils and what they can tell us about the Earth's past.

What evidence for evolution is shown in the fossil record?

- Fossils of simple organisms in oldest rocks, more complex organisms in youngest rocks.
- Ecological sequencing is consistent. I.E. fossil plants appear before fossil animals (animals need plant to survive)
- Studying the similarity in fossil anatomy, we can see the links between organisms and the evolution from a common ancestor.
- The link between living and extinct organisms can be investigated.

Why is the fossil record not complete?

- Many organisms are soft bodied and therefore decompose
- The conditions aren't right for fossilisation
- Fossils may be destroyed by the Earth's movement

What is comparative anatomy?

The study of similarities and differences in the anatomy of living species.

What is a homologous structure?

A structure which appears differently in different organisms, but has the same underlying structure, eg the pentadactyl limb of vertebrates.

What do homologous structures provide evidence for?

Divergent evolution

What is divergent evolution?

The description of different organisms evolving from a common ancestor.

What is comparative biochemistry?

The study of similarities and differences in the proteins and other molecules that control life proceses.

How are molecules used in comparative biochemistry?

Some molecules are important for all life and remain highly conserved (don't change much). Slight changes in these molecules over time and between species can be used to identify relationships. The greater the similarity, the closer the relationship.

Which molecules can be used in comparative molecular biochemistry?

Cytochrome C (used in respiration)
Ribosomal RNA.

What are the two types of variation between organisms?

Interspecific and intraspecific

What is interspecific variation

Variation between organisms of different species

What is intraspecific variation?

Variation between organisms of the same species

What are the causes of variation?

1 - Genetic
2 - Environmental

What are the causes of genetic variation?

1 - Alleles
2 - Mutations
3 - Meiosis
4 - Sexual reproduction (2 partners)
5 - Chance

How do alleles cause genetic variation?

Alleles are varient forms of a gene. Different alleles produce different affects and different characteristics. Individuals of a species may inherit different alleles.

How do mutations cause genetic variation?

Mutations are changes to the DNA sequence, and therefore the proteins the genes code for. this can affect the physical and metabolic characteristics.

How does meiosis cause genetic variation?

Meiosis is the formation of gametes. During this process the independent assortment of chromosomes and the crossing over (creating chiasmata) occurs. This leads to genetically unique sex cells.

How does sexual reproduction (2 partners) cause genetic variation?

During sexual reproduction, the offspring inherits genetics from both parents, therefore being their own different organism.

How does chance cause genetic variation?

During sexual reproduction, any 2 of the many gametes are produced could end up combining. This is random fertilisation, it is why siblings differ from one another.

Why is there much more variation in sexually reproductive organisms than those which reproduce asexually?

Meiosis, sexual reproduction (2 partners) and chance are all aspects of sexual reproduction. There is therefore more likelyhood of variation through this process.
Asexual reproduction results in the creation of clones.

Are animals or plants more likely to be affected by the environment and cause variation? Why

Plants, as they lack mobility.

Give an example of a purely environmental variation.

The presence or absence of scars. these can not be inherited.

In most cases, what causes variation within a population?

Both genetic and environmental causes.

Give an example of a charachteristic that can be affected by both genetic and environmental factors.

Height - you can inherit the genes to allow you to grow, but if your diet is poor, you may not be able to reach your potential height.
Skin colour - your skin colour is determined by genes, though exposure to sunlight and UV rays will darken the skin.

It is hard to separate genetic and environmental factors from causing variation. What investigations are done to allow better understanding between nature and nurture?

Twin studies, especially twins who have been separated and brought up in different environments.

Into which 2 groups can data on characteristic variation be sorted?

Discontinuous and continuous variation.

What is another term for discontinuous variation?

Discrete variation

What is discontinuous variation?

Variation that can only be put into particular categories, or results in certain values.

Give an example of discontinuous variation.

- An animals sex,
- The shape of a bacteria
- Human blood group

What causes discrete variation?

A characteristic purely determined by genetics, typically a single gene.

How is discontinuous variation displayed graphically?

Using a bar chart.

What is continuous variation?

A characteristic that can take any value within a range. Thare is a gradual change from one extreme to another.

What is an example of continuous variation?

- Height
- Mass

What causes continuous variation?

- Multiple genes determining that characteristic (polygenes) also influenced by the environment.

How is continuous variation displayed graphically?

- Collected on a frequency table
- Histogram drawn
- Curve drawn onto graph

Continuous variation typically show what distribution?

Normal distribution.

What is normal distribution?

Data that creates a bell curve when plotted.

What are the characteristics of normal distribution?

- Mean, median and mode are the same
- Distribution is a bell curve, symetrical about the mean
- 50% of values are less than the mean, and 50% greater
- Most values are close to the mean, the values at the extremems are low.

What is standard deviation?

A measure of how spread out the data is.

What does the variation look like if there is a high standard deviation?

A large amount of variation.

What does the variation look like if there is a low standard deviation?

A small amount of variation.

In normal distribution, what are the typical values for the first 3 standard deviations?

1 SD - 68% of values
2 SD - 95% of values
3 SD - 99.7% of values

What What do the symbols in the standard deviation formula stand for?

σ - Standard Deviation
∑ - Sum of (add all the numbers together)
x - measured value
x ̅- mean value
n - total number of values

What is the Student's t test used for?

Comparing the averages of data values between two populations. (Are two populations statistically similar or different?)

What is Spearman's rank correlation coefficient used for?

Considering the relationship between two sets of data. (is there a correlation or not, if so is it positive or negative?)

What are the purpose of statistical tests?

To determine wether any relationship or outcome is due to chance, or an outside factor effecting the organisms. It determines the significance of the data.

What is a null hypothesis in a Student's t test?

The prediction that there is no significant difference between the populations. Any observed difference is due to chance.

What is a null hypothesis in a Spearman's rank?

The prediction that there is no significant relationship between the data. Any observed relationship is due to chance.

What are the degree of freedom in a Student's t test?

It describes how much data was collected. It is calculated by (n1 + n2) -2

How do you determine significance in a Studen't t test?

The value of "t" is looked up in the Student's t test significance tables comparing the probability value to the degrees of freedom. For the data to be significantly different to chance alone, the value of "t" must be lower that a probability 5% or 0.05.

What do the probability values in the significance tables mean?

how likely the effect observed is down to chance. We use the 5% (0.05) probability value.

How do you determine significance in a Spearman's rank?

The value of the correlation coefficient is looked up in the Spearman's rank significance tables comparing the probability value to the number of values, "n". For the data to be significantly different to chance alone, the value of "t" must be lower that a probability 5% or 0.05.

What are adaptations?

Characteristics that allow an organism to survive and reproduce in it's environment.

What are the 3 types of adaptation?

Anatomical; behavioural; physiological.

What is an anatomical adaptation?

A physical feature, internal or external.

What is a behavioural adaptation?

The way an organism acts, either inherited or learned from parents.

What is a physiological adaptation?

A process that goes on inside an organism.

Give an example of an anatomical adaptation.

Body coverings - such as a shell, hair or feathers
Camouflage - to blend in with the environment so as not to be seen
Teeth - the shape and type allows different food to be eaten
Mimicry - copying another organisms appearance or sound to fool predators

How is Marram grass adapted to stop transpiration?

Curled leaves - minimise exposed area of leaves
Hairs on inside - trap moist air increasing humidity
Sunken stomata - less likely to loose water
Thick waxy cuticle - reduces water loss through evaporation

Give an example of a behavioural adaptation.

Survival - eg playing dead
Courtship - eg mating dances
Seasonal - eg migration or hibernation

What are the two main types of behavioural adaptation?

Innate; learned

What is an innate behaviour?

Instinctive, it is inherited through genes, e.g. avoiding light, building webs.

What is a learned behaviour

Developed through experience and observation, e.g. use of tools, language.

Give an example of physiological adaptations.

Poison production
Antibiotic production
Water storing
Reflexes
Homeostasis

What is convergent evolution?

Where two unrelated species develop traits or characteristics. Same function, but different genetic origin.

Why does convergent evolution occur?

The unrelated organisms live in similar environments and are experiencing similar selection pressures

What is natural selection?

THe process by which organisms best suited to their environment survive and reproduce, passing on their characteristics to their offspring through their genes.

What are the steps involved in natural selection?

1 - Organisms within a species show variation;
2 - Organisms best adapted to a selection pressure are more likely to survive and reproduce;
3 - Successful organisms pass the allele encoding the advantageous characteristic to their offspring;
4 - This proccess is repeated each generation, and the frequency of the advantageous allele increases;
5 - Over a very long time period, this process may lead to the evolution of a new species.

What is a selection pressure?

Factors which affect an organisms chance of survival mor reproductive success.

What are examples of selection pressures?

Predation;
Competition (mates / resources);
Disease;
Etc.

What are modern examples of evolution?

Anti-biotic resistant bacteria;
Peppered moths;
Sheep blowflies;
Flavobacterium.

How does anti-biotic resistant bacteria show modern evolution?

Methicillin-resistant Staphylococcus aureus has become resistant to many anti-biotics. As the bacteria were exposed to them, some which were resistant, survived and reproduced. They passed on the allele for resistance.

How do peppered moths show modern evolution?

Changes to the environment changed the allele frequency in the peppered moths.
Before the industrial revolution pale moths were camoulfaged against pale trees.
During the revolution, the trees were black with soot. Dark moths were better adapted and their frequency incresed.
After the clean air act, the trees are now clean again, and the pale moths have increased in frequency.

How do sheep blowflies show modern evolution?

A pesticide was used to kill off the blowflies.
A resistance quickly appeared, this was passed though generations allowing a resistant population to evolve.
When studied it was revealed that blowflies had a resistance to a previous pesticide.
The mutation of the old allele allowed much more rapid evolution to occur.

How do Flavobacterium show modern evolution?

An example of a positive selection pressure.
The bacteria are found in the waste water of nylon producing factories.
A mutation has allowed them to use the waste as an energy source.
The bacteria can now be used in bioremediation.

What is biodiversity?

The variety of living organisms in an area.

Why is biodiversity important?

Biodiversity allows a balanced ecosystem. Many organisms rely on one another, they are interconnected.

Why do humans rely on balanced ecosystems?

They supply us with oxygen, food, and other materials for survival.

How can human activities lead to a reduction in biodiversity?

Farming, clearing land for housing can remove biodiversity.

What are the 3 ways of measuring biodiversity?

1 - Habitat biodiversity;
2 - Species biodiversity;
3 - Genetic biodiversity.

Why is it important to measure biodiversity?

Supports conservation, giving a baseline for scientists to monitor changes.

What is habitat biodiversity?

This refers to the number of habitats found within an area. In general the greater the habitat biodiveristy, the greater the species biodiversity.

What is species biodiversity?

A measure of the species present within an area. Made of 2 components:
1 - Species richness;
2 - Species evenness.

What is species richness?

The number of different species living within an area.

What is species evenness?

A comparison of the numbers of individuals of each species in a community.

What is a community?

All of the populations of living organisms in a particular habitat.

What is genetic biodiversity?

This refers to the variety of genes making up an organism. It also takes into account the different alleles that exist for those genes. This is what created variation within a species.

Why is genetic variation important?

Greater genetic variation within a species allows for better adaptation to a changing environment.

What is sampling?

Taking measurements of a limited number of organisms of an area.

Why is sampling important?

It is often impossible to count / measure all of the organisms in a particular area.

What is sampling used for?

It can be used to:
1 - estimate the number of organisms of an area;
2 - estimate a particular characteristic of an organism.

What are the 2 ways sampling can be carried out?

Random and non-random.

What is random sampling?

Selecting individuals by chance, each individual has an equal likelihood of being selected.

How is random sampling carried out?

A random number generator is used, The scientist is not involved in choosing at all. Often 2 tape measures are laid out as a grid, random numbers generate coordinates. Samples are taken here.

What is non-random sampling?

This is where the sample is chosen, or selected.

What are the 3 main types of non-random sampling?

1 - Opportunistic;
2 - Stratified;
3 - Sytematic.

What is opportunistic sampling?

Weakest form of sampling. May not be representative of the population. Measures the organisms conveniently available.

What is stratified sampling?

Separating populations into strata (sub-groups). e.g. male / female. Random sampling is done on these proportional to their size.

What is systematic sampling?

Different areas within a habitat are defined, and then sampled separately. e.g. the change in organisms as you move inland from the sea.

What are two techniques that could be used in systematic sampling?

Line transect and belt transect.

What is a line transect?

A line is marked between two points. Samples are taken at specified points. Everything touching the line is counted.

What is a belt transect?

2 parallel lines are marked, and samples are taken in the area between the lines. More information gathered than with a line transect.

What is an interupted belt transect?

A line transect is drawn. A quadrat is placed at regular intervals. A sample is taken from within the quadrat.

What is reliability?

A measure of how representative of the organisms present in the habitat the sampling is. How accurate the sampling is.

What can decrease the reliability of the sampling being done?

1 - Sampling bias
2 - Chance

What is sampling bias?

Accidental or deliberatly choosing a particular area to sample. This effect is reduced by random sampling.

What is chance?

The organisms selected may not be representative of the whole population. Chance can not be removed, but its effect can be reduced by having a large sample size.

What are the techniques used in collecting live animal samples?

1 - Pooter;
2 - Sweep nets;
3 - Pitfall traps;
4 - Tree beating;
5 - Kick sampling.

How is a pooter used?

It collects small insects by drawing them into a holding chanber by sucking on a mouthpiece.

How are sweep nets used?

By sweeping long grass, they collect insects.

How are pitfall traps used?

They collect small crawing invertebrates. A hole is dug in the ground which they fall into and can't climb out of.

How is tree beating used?

A large white cloth is laid under a tree or bush. This collects invertebrates knocked off as the tree is shaken.

How is kick sampling used?

The riverbed is gently kicked to disturb substrate. A net is held just downstream to collect organisms released into the water.

How are plants generally sampled?

Using a quadrat. Either frame quadrat or point quadrat.

What is a point quadrat and how is it used?

A frame with a horizontal bar. Down which long pins can be dropped. Any plant touching the pin will be recorded.

What is a frame quadrat?

A square frame, divided into smaller equal sections. The type and number of each species within a section is recorded.

What is the most valid way of sampling an area?

Random sampling using quadrats.

What is the most valid way of sampling the change in distribution of species across an area of land?

Laying quadrats along a line or belt transect.

How is species richness measured?

A variety of sampling techniques is used to identify all species present in a habitat. A list is created and the total number calculated. An identification key may be used to accurately identify organisms.

How is species evenness measured?

A variety of sampling techniques is used to identify both the species, and number of idividuals in those species present in a given habitat. They are then number of individuals per species is compared to identify how evenly distributed they are.

What are the different types of data that can be collected using frame quadrats?

1 - Density;
2 - Frequency;
3 - Percentage cover.

How and when is density measured using a frame quadrat?

This is an absolute measure of individual plants in a specific area. E.G. count the number of dandelions in 1m2 gives density per square meter.

How and when is frequency measured using a frame quadrat?

If the plants are too small to count. Count the number of squares in which they are present. Give this as a percentage of the total number of squares in the quadrat.

How and when is percentage cover measured using a frame quadrat?

Used for speed when there is abundant plants which are difficult to count. An estimation of the cover is done by eye, using the quadrat and its squares as a guide.

How is the use of quadrats made more reliable?

Multiple samples are taken from an area. The mean is then calculated. To calculate the total cover for that area, the mean value per m2 is multiplied by the total area.

How is a mean calculated?

Add the individual results, then divide by the number of repeats.

How is animal population size estimated?

Using capture - mark - release - recapture.

Why is measuring animal population size difficult?

The animals move about, they may be hidden, they go through different stages of development, so may be hard to identify.

What are abiotic factors?

Non-living conditions in a habitat.

What are common abiotic factors?

- Wind speed
- Light intensity
- Humidity
- pH
- Temperature
- Oxygen content in water.

What formula is used to calculate biodiversity?

Simpson's index of biodiversity.

In Simpson's index of diversity, what do D, n and N stand for?

D - Is the measure of diversity
n - is the sum of organisms of a particular species
N - is the total number of organisms of all species

When D is calculated in the Simpson's index of diversity, what does it mean?

The value falls between 0 and 1. 0 is no diversity, 1 is infinite diversity. A higher value means a more diverse habitat.

What are the characteristics of a low biodiversity habitat?

1 - Few successful species
2 - stressful / extreme. Few ecological niches
3 - Species have very specific adaptations
4 - Simple food webs
5 - Environmental change has a major effect on the ecosystem

What are the characteristics of a high biodiversity habitat?

1 - Many successful species
2 - Benign environment, many ecological niches
3 - Species have few specific adaptations
4 - Complex food webs
5 - Environmental change has a relatively minor effect on the ecosystem

What is genetic biodiversity?

This refers to the variety of genes making up an organism. It also takes into account the different alleles that exist for those genes. This is what created variation within a species.

Why is genetic biodiversity important?

Species with greater genetic biodiversity are more likely to survive changes to their environments. They will be more likely to reproduce, and then allow the species to survive.

What are the factors that affect genetic biodiversity?

1 - Mutations
2 - Interbreeding (gene flow)
3 - Selective breeding (artificial selection)
4 - Captive breeding
5 - Rare breeds
6 - Artificial cloning
7 - Natural selection
8 - Genetic bottlenecks
9 - The founder effect
10 - Genetic drift

How do mutations affect the genetic biodiversity?

They change the DNA, and can create new alleles. Increases genetic biodiversity.

How does interbreeding (gene flow) change the genetic biodiversity?

Individuals moving from one population to another and breeding, will cause alleles to transfer between populations. Increases genetic biodiversity.

How does selective breeding (artificial selection) change the genetic biodiversity?

Only a few individuals are selected from a population to breed due to their advantageous characteristics. Decreases genetic biodiversity.

How does captive breeding change genetic biodiversity?

Only a few individuals are present in zoos or conservation centers, the gene pool is relatively small. Wild population is often endangered or exdtinct. Decreases genetic biodiversity.

How do rare breeds change genetic biodiversity?

Selective breeding has produced a breed of domestic animal/plant which is no longer popular. Therefore the population number is small, and as it has been selected for particular traits, the gene pool is very low. Decreases genetic biodiversity.

How does artificial cloning change genetic biodiversity?

Cloning animals and plants produces genetically identical organisms. Decreases genetic biodiversity.

How does natural selection change genetic biodiversity?

Species evolve to contain the alleles which code for advantageous characteristics. Over time the alleles for less advantageous characteristics become removed. Decreases genetic biodiversity.

How do genetic bottlenecks change genetic biodiversity?

Few individuals from a population survive a catastorphic event. Therefore the gene pool is reduced. Only the alleles of the survivinig members are available to be passed on to their offspring. Decreases genetic biodiversity.

How does the founder affect change genetic biodiversity?

A small number of individuals start a new population. They are genetically isolated. The gene pool is small, and gene flow does not happen. Decreases genetic biodiversity.

How does genetic drift affect genetic biodiversity?

Due to the random nature of alleles being passed on to subsequent generations, the frequency of a particular allele can vary from generation to generation. In some cases it may even disappear. This effect is more pronounced in populations with a low genetic biodiversity. Decreases genetic biodiversity.

What are polymorphic genes?

Genes which have more than one allele.

Why are most genes not polymorphic?

By having a single allele for most genes, the basic structure of an individual within a species remains consistent.

How can we measure genetic biodiversity?

By measureing the proportion of genes that are polymorphic.
Proportion of polymorphic gene loci = (number of polymorphic gene loci / total number of loci)

What is the locus of a gene?

The position of the gene on a chromosome.

How does the proportion of polymorphic gene loci relate to genetic biodiversity?

The greater the proportion of polymorphic gene loci, the greater the genetic biodiversity within the population.

Describe one way of how deforestation can affect biodiversity.

Trees' species diversity decreases; Habitats destroyed, leading to decline in animal species population/diversity; Forced migration, increasing biodiversity in other areas

Describe one way of how agriculture can affect biodiversity.

Deforestation; Hedgerow removals, destroying habitats of small animals; Use of pesticides and herbicides; Monoculture

Describe on way of how climate change can affect biodiversity.

Global warming leading to habitats or food sources destroyed

Give three reasons for maintaining biodiversity.

Asthetic reasons (for people to enjoy, provide inspirations etc.); Economic reasons (Deforestation leads to soil erosion and desertification, fail to grow crops, potential loss of useful species in research and medicine); Ecological reasons (affect keystone species which then has a knock-on effect on other species and the environment)

Define 'keystone species'.

Species that are essential for maintaining biodiversity, have a disproportionately large effect on their environment relative to their abundance

What is the difference between 'in situ' and 'ex situ' conservation? Give an example for each.

in situ = within natural habitat (eg. wildlife reserves, marine conservation zones); ex situ = out of natural habitat (eg. zoos, botanic gardens, seed banks)

What is the IUCN?

The IUCN updates conservation status of threatened species and also established CITES

What is the CITES?

A treaty that regulates the international trade of wild species and their products to prevent over-exploitation

What is the Rio Convention?

Made up of 3 parts - sustainable development, stabilise greenhouse gas conc to tackle climate change, combat desertification

What is the Countryside stewardship scheme?

UK conservation scheme to make conservation a part of normal faming and land management practice

State the kingdom of organism that causes each of the following diseases: tuberculosis, Black Sigatoka, Athlete's foot, malaria

Bacteria, fungi, fungi, protoctists

State the kingdom of organism that causes each of the following diseases: blight, ringworm, ring rot, bacterial meningitis

Protoctists, fungi, bacteria, bacteria

Give one plant disease caused by each of the following: viruses, bacteria and fungi

Tobacco mosaic virus, ring rot, black sigatoka

State three factors that would affect the speed of disease transmission in plants

Overcrowding; poor mineral nutrition; damp, warm, humid conditions; climate change

State how the influenza virus is most likely to be transmitted between different humans

Respiratory droplets (inhalation)

State four different types of vector that can be used to transmit a communicable disease

Water (e.g. diarrhoeal diseases); animals (e.g. mosquito transmits Plasmodium); wind (carries spores); humans (hands, clothing etc.)

State three passive physical defences that prevent plants being infected by a pathogen

Bark, waxy cuticle, thorns, spines, lignified cell walls, cellulose etc.

State three active physical defences a plant would employ against an invading pathogen

Callose synthesised and deposited between plasma membrane and cell wall; callose blocks sieve plates in phloem; callose deposited in plasmodesmata between infected cells and their neighbours; lignin added to cell walls; tyloses block xylem vessels

State three chemical defences a plant would employ against an invading pathogen

Antibacterial compounds like phenols, alkaloids; terpenes; hydrolytic enzymes like glucanases and chitinases; caffeine; tannins etc.

Describe the role of the skin as a primary non-specific defence

Dead outer layer of keratin prevents pathogen entry; skin flora outcompete pathogens for space; oil secretions inhibit pathogenic growth

Describe the role of mucous membranes as a primary non-specific defence

Mucus traps pathogens and contains lysozymes; phagocytes engulf and digest pathogens in mucus

Which enzyme catalyses the conversion of prothrombin to thrombin

Thromboplastin (thrombokinase)

Describe the role of thrombin in the clotting process

Causes the conversion of soluble fibrinogen into insoluble fibrin fibres

Describe the process of inflammation as a secondary non-specific response

Mast cells release histamines;
histamines increase permeability of capillaries meaning plasma leaks into tissue fluid (pain and swelling);
vasodilation of arterioles so more blood reaches infected area (heat and redness);
neutrophils attracted to area for enhanced phagocytosis

Describe the process of phagocytosis

Phagocyte engulfs pathogen into a phagosome; lysosomes fuse with phagosome to form a phagolysosome; enzymes, hydrogen peroxide and nitric acid break down the pathogen

Describe how macrophages process antigens for presentation on their cell surface membrane

Antigen fragments combined with MHC (special glycoproteins in cytoplasm)

What name is given to small protein molecules that act as cell-signalling compounds?

Cytokines

Describe how neutrophils are specialised for their role

Plasma membrane contains receptors for opsonins, well developed cytoskeleton for phagocytosis, many mitochondria for respiration, many ribosomes to make enzymes, many lysosomes.

Opsonins are non-specific. Explain why

Opsonins can attach to many types of pathogen and help the process of phagocytosis, by giving the phagocyte something to bind to. They must be non-specific, so they can attach to many different pathogens.

Where do B lymphocytes and T lymphocytes mature?

Bone marrow and thymus respectively

What is meant by the term 'autoimmunity' and give two examples of autoimmune diseases

Destruction of self-tissue; rheumatoid arthritis, lupus, type I diabetes

What is the role of T regulatory cells?

Dampen down the immune response; prevents destruction of self tissue (autoimmunity)

Describe how an antigen presenting cell leads to large numbers of T helper cells

APC binds specifically to a Th cell (clonal selection). This selected Th cell then proliferates by mitosis (clonal expansion)

Describe how B lymphocytes are activated and the role of activated B lymphocytes

Th cell binds specifically to B lymphocyte; B lymphocyte differentiates into a plasma cell. Plasma cells release antibodies specific to the particular antigen

Describe how T killer cells destroy a virally infected cell

Release perforins which punch holes in the membrane of the cell; Tk cell inserts channels through which it floods hydrogen peroxide/nitric acid/hydrolytic enzymes

Dinstinguish clearly between an antigen and an antibody

An antigen is a cell-surface molecule that is specific to the cell (and a particular antibody); an antibody is an immunoglobulin manufactured by the plasma cells (which binds specifically to an antigen).

Antibodies are made by plasma cells. Explain how plasma cells are specialised for their role

Plasma cells have a lot of ribosomes, rough endoplasmic reticulum, Golgi apparatus and mitochondria.

Describe how opsonins function

Opsonins bind specifically to an antigen on a pathogen (via the variable region), clearly marking the pathogen for destruction by a neutrophil. A neutrophil will bind to the constant region of the opsonin and destroy the pathogen by phagocytosis

Describe how agglutinins function

Agglutinins cross link pathogens by binding specifically via their variable regions. Pathogens are clumped together (agglutinated), meaning they cannot enter host cells and are easier to phagocytose

Describe how antitoxins function

Neutralise toxin molecules released by a pathogen through direct binding

Describe how the structure of an antibody enables it to perform its function

The variable region is specific to the antigen – it has a shape that is complementary to the shape of the antigen; the disulfide bridges hold the four polypeptide chains together; the hinge region allows some flexibility so that the molecule can bind to more than one antigen; the constant region may have a shape that can be recognised by the neutrophils.

Explain why it may take several days for the primary immune response to become effective

After infection, the pathogen must be detected and attacked by macrophages; antigen presentation occurs to select the correct B and T cells (clonal selection); these cells must reproduce in clonal expansion; then they must differentiate to form plasma cells; the plasma cells must start to produce the antibodies – each step takes time.

Explain why a secondary immune response is so much faster than a primary immune response

B memory and T memory cells are circulating in the blood. On second encounter with a pathogen, the correct B/T memory cell is clonally selected and can very quickly differentiate into correct specific Th/Tk/plasma cell. Plasma cells can produce antibodies faster, sooner and in much greater quantity. Pathogens are wiped out before symptoms are experienced; level of antibody stays higher for longer

Give an example of both natural active immunity and natural passive immunity

Natural active - antibodies made by immune system in response to infection; natural passive - antibodies provided via placenta/breast milk (useful in developing immune system)

Explain why passive immunity only provides short-term immunity

Passive immunity is provided by an external supply of antibodies – these are proteins and will not last long in the body. They may even act as antigens and be attacked by antibodies from our immune system.

Give an example of artificial active immunity

Immunity provided by antibodies made in response to vaccination (dead/inactive pathogens injected)

Define the term epidemic

A rapid spread of disease through a high proportion of a population (usually within a country)

Describe the difference between herd vaccination and ring vaccination

Herd vaccination is where everyone, or almost everyone, is vaccinated. Ring vaccination is vaccinating people around the site of the outbreak, so that the pathogen will not be transmitted across that ring to the whole population.

Describe how a microorganism can become resistant to an antibiotic

Bacteria that survive a treatment will be slightly resistant to the antibiotic and the antibiotic acts as a selective force which selects the resistant individuals. When they reproduce, some of their offspring may be more resistant, thus resistance evolves.