Genetics, Populations, Evolution & Ecosystems

Question 1

Define the difference between a genotype and phenotype

Answer 1

Genotype- The genetic makeup of an organism. It determines the potential traits expressed

Phenotype- Observable characteristics resulting from the genotype and environmental factors

Question 2

What are homologous chromosomes?

Answer 2

pair of chromosomes in a diploid organism with similar genes

Question 3

What are the three types of alleles?

Answer 3

Dominant- Only one allele needed for expression

Recessive- requires two alleles for expression

Codominant- both alleles are expressed leading to a blend of combined phenotype

Question 4

What is monohybrid inheritance?

Answer 4

the inheritance of a trait controlled by a single gene, for example: When A green pea pod (GG) x Yellow Pod (gg) resulting in all offspring being green.
When crossed, they produce a 3:1 ratio of green to yellow pod.

Question 5

What is Dihybrid Inheritance?

Answer 5

The inheritance of two different characteristics controlled by two different genes located on separate chromosomes. For example,
- Seed shape (R): Round (R) is dominant, wrinkled (r) is recessive.
- Seed color (Y): Yellow (Y) is dominant, green (y) is recessive.
When crossed, this forms a 9:3:3:1 cross with round yellow: round green: wrinkled yellow: wrinkled green

Question 6

What is co-dominance (give an example)?

Answer 6

when two genotypes are expressed in the phenotype because neither one is recessive.
Human blood groups- The A and B alleles are co-dominant, so individuals with genotype I^A I^B express both A and B antigens on their red blood cells, resulting in the AB blood group.

Question 7

Talk about multiple alleles.

Answer 7

situation where a gene has more than two different versions (alleles) in the population. For example, the gene for blood type in humans has three alleles: A, B or O

Even though there are multiple alleles, an individual can only inherit two alleles (one from each parent)

Question 8

What is linkage?

Answer 8

Linkage is when genes that are close to one another on a chromosome are likely to be inherited together.

Question 9

What is an autosome?

Answer 9

are all the chromosomes except the sex chromosomes. They are arranged in pairs called homologous chromosomes that consist of the same genes in the same order along the chromosome

Question 10

Talk about autosomal linkage?

Answer 10

the exchange of sections of the homologous chromosomes. If two genes are located in close proximity on the same chromosomes are more likely to be exchanged together and not separated in recombination so are more likely to be transmitted together-

Question 11

Talk about sex linkage.

Answer 11

genes that are located on the sex chromosomes (X and Y) are inherited differently in males and females because males have one X and one Y chromosome, while females have two X chromosomes

Sex- linked characteristics mean the alleles that code for them are located on a sex chromosome

Question 12

What is epistasis (give an example)?

Answer 12

when one allele of one gene masks or blocks the expression of the alleles of another gene.

One example is flower pigment in a plant. Gene one coats for yellow pigment. Yellow is the dominant allele. And gene 2 codes for an enzyme that turns the yellow pigment to orange. If you don’t have the yellow allele, it won’t matter if you have the orange alloy or not, as the flower will be colourless. Gene 1 is epistatic to gene 2.

Question 13

Talk about the chi-Squared Test

Answer 13

statistical test that is used to see the extent of how similar the expected result is compared to the actual result.
First, the theory is used to predict a result. This is called the expected result. Then the experiment is carried out and the actual result is recorded. This is called the observed result.

• always include a null hypothesis, if results are more then critical value, reject the null hypothesis.

Question 14

Define population

Answer 14

A population is a group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed.

Question 15

Define gene pool and allelic frequency

Answer 15

Gene pool- The total number of alleles that are present in a population
Allelic Frequency- how often an allele occurs in a population given as a decimal or percentage.

Question 16

What is the Hardy- Weinberg principle?

Answer 16

This is a mathematical model which predicts the frequency of alleles in a population to see whether a change in allele frequency is occurring over time.

Question 17

What do we assume while conducting the hardy- Weinberg principle

Answer 17

• no mutations
• no movement of alleles into or out of population by migration
• the population is large
• no selection- equal chance of being passed
• mating is random

Question 18

Talk about the allele frequency equation.

Answer 18

The total frequency of all possible alleles is 1.0 or 100%. So the frequency of the individual alleles must add up to one. Therefore:

p + q = 1

where p = frequency of dominant allele, q = recessive

Question 19

Talk about the genotype frequency equation

Answer 19

The total frequency of all genotypes for one characteristic in a certain population in 1.

p^2 + 2pq + q^2 = 1

p^2 = homozygous dominant, 2pq = heterozygous, q^2 = homozygous recessive

Question 20

Define Variation

Answer 20

This is the differences that exist within individuals. Variation within a species means individuals in a population can show a wide range of phenotypes.

Question 21

Define Evolution

Answer 21

This is when the frequency of an allele in a population changes overtime. This can occur by genetic drift or natural selection

Question 22

Talk about Natural Selection

Answer 22

Selection preassures are preassures that affect organisms chances of surviving. Due to individuals in species having different alleles, there is variation, this means that some our better adapted to selection preassures than others. This means there is differing chances of survival.

Individuals with a phenotype that increases their chances of survival are more likely to survive, reproduce and pass on their adventagous alleles than individuals with a different phenotype. This increases the allele frequency of the beneficial alleles in the gene pool and further increases from generation to generation.

Question 23

What are the three types of natural selection?

Answer 23

• Stabalising
• Directional
• Disruptive

Question 24

Talk about stabalising selection.

Answer 24

This is when individuals with alleles for characteristics towards the middle of the range are more likely to survive. This occurs when the environment isnt changing.

Question 25

Talk about Directional Selection

Answer 25

This is when individuals with alleles for a single extreme phenotype are more likely to survive and reproduce, this could be in response to environmental change

Question 26

Talk about Disruptive selection

Answer 26

When individuals for extreme phenotypes are more likely to survive and reproduce loosing the middle characteristics. It occurs when the environment favours more than one phenotype

Question 27

What is speciation?

Answer 27

This is the development of a new species from an existing specie. This occurs when populations of the same species become reproductively isolated- changes in allele frequency cause changes in phenotype mean they can’t interbreed

Question 28

Talk about Allopatric Speciation

Answer 28

This is when popualtions are geographically isolated and so experience different conditions. The separate populations experience different selection preassure and so different changes in alleles via natural selection and mutations. Overtime, the populations will become so different, they wont be able to breed and so become reproductively isolated.

Question 29

Talk about Sympatric speciation

Answer 29

This occurs when random mutations within a population prevent individuals from mating. It is pretty rare.

Question 30

What is genetic drift

Answer 30

Instead of environmental factors affecting which individuals survive, breed and pass on their alleles, change dictates which alleles are passed on.

Question 31

Talk about the process of genetic drift

Answer 31

- Individuals within a population show variation in their genotypes. - By chance, the allele for one genotype is passed on to more offspring than others, so the number of individuals with the allele increases. - If by chance the same allele was passed on more often again and again, it can lead to evolution as the allele becomes more common in the population.

Question 32

What is an ecosystem

Answer 32

An ecosystem is all the organisms living in a community, plus or the nonliving abiotic conditions in the area in which they live. Biotic being conditions that are living for example, predators, abiotic, non living features such as temperature

Question 33

What is an ecological niche?

Answer 33

These are the roles of a species within its habitat. For example, what it eats. This includes a species abiotic and biotic interactions. species has its own niche. Niche can only be occupied by one species. It may look like two species are filling the same niche, but they'll be slight differences

Question 34

What is a carrying capacity?

Answer 34

the maximum stable population size of a species that an ecosystem can support

Question 35

Talk about Interspecific Competition

Answer 35

This is when organisms of different species compete with each other for the same resources. This. can mean that the resources available to both populations are reduced. Both populations are limited by a lower. amount of food so will have less energy for growth and reproduction. So population sizes will be lower for both species. If two species are competing but one is better adapted to its surroundings than the other is likely to be outcompeted

Question 36

Talk about Intraspecific Competition

Answer 36

This is when organisms of the same species compete with each other for the same resources It can cause a cyclical change in population size around the ecosystems carrying capacity. This is because the population of a species increases when resources are plentiful and decreases when limiting

Question 37

What is predation?

Answer 37

Predation is where an organism kills and eats another organism The population sizes of predators and prey are interlinked as the population of one changes. It causes the other population to change as the prey population increases. There's more food for predators, so predators as population grows. As the predator population increases, more praise eaten so the prey population then begins to fall. This means less food for predators and population decreases

Question 38

What does investigating population involve looking at?

Answer 38

Abundence- This is the number of individuals of one species in a particular area. It can. be estimated by simply counting the number of individuals in samples taken. it can also be the frequency or percentage cover. Distribution- where a particular species is within the area you’re investigating

Question 39

Talk about quadrats?

Answer 39

Quadrats are placed on the ground at different points within an area. The species frequency or the number of individuals of each species is recorded in each quadrat. The percentage cover can also be measured by counting how much of the quadrat is covered by the species.

Question 40

Talk about transcets?

Answer 40

You can use lines called Transects to help you find out how organisms are distributed across an area. You can do this by belt transects, which are placed next to each other along the transect or interrupted belt transects, where you can take measurements and place at regular intervals.

Question 41

Talk about the process of mark- release- recapture.

Answer 41

1. 1. capture a sample of species using an appropriate technique and count them. 2. Mark them in harmless way by using. an identification tag. 3. Release them back. 4. Wait a week, then take a second sample from the same population. 5. Count how many of the 2nd sample are marked then use the equation to estimate total population size

Question 42

Talk about assumptions made by mark- release- recapture method.

Answer 42

- The marked sample has had enough time to mix back with the population - The marking hasn't affected the individuals chance of survival. - There are no changes in population size

Question 43

What is succession?

Answer 43

Succession is the process by which an ecosystem changes over time. It happens in a series of stages. At each stage, the plant and animal communities in an area change the environmental conditions making the conditions more suitable for other species with different adaptations.

Question 44

What's the difference between primary and secondary succession?

Answer 44

Primary Succession- This is when succession happens on land that has been newly formed or exposed. There is no soil or organic matter to start with Secondary Succession- This happens on land that's been cleared of all the plants, but where the soil remains. The established community of species is usually destroyed, but without too much disturbance to the soil.

Question 45

Talk about the process of succession

Answer 45

Species colonise a new land or surface seed. seed and spores are blown in by the wind and begin to grow. The first species to colonise are called pioneer species. Due to conditions being hostile, only pioneer species can grow because they're specially adapted to cope. The new organisms then die and are decomposed, adding more organic matter (hummus), making the soil deeper and richer in minerals. Nitrogen fixing bacteria take nitrogen from the atmosphere into ammonia. This forms ammonium ions in the solution that can then be used by plants. This means larger plants like shrubs can start to grow, which retain more water and contain more nutrients As succession goes on, the ecosystem becomes more complex. New species move in alongside existing species, meaning that biodiversity increases. Plants create more habitats for animals that abiotic conditions become less hostile, and the amount of biomass increases. Eventually, these changes result in a climax community. The ecosystem is supporting the largest and most complex community of plants and animals it can. It won't change much more

Question 46

What is conservation?

Answer 46

Conservation is the human management of the Earth’s resources and typically involves the managing of succession. For example the controlled burning of land is done in order to stopthe formation of a climax community