Genetics, Populations, Evolution & Ecosystems Flashcards
Define the difference between a genotype and phenotype
Genotype- The genetic makeup of an organism. It determines the potential traits expressed
Phenotype- Observable characteristics resulting from the genotype and environmental factors
What are homologous chromosomes?
pair of chromosomes in a diploid organism with similar genes
What are the three types of alleles?
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
What is monohybrid inheritance?
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.
What is Dihybrid Inheritance?
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
What is co-dominance (give an example)?
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.
Talk about multiple alleles.
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)
What is linkage?
Linkage is when genes that are close to one another on a chromosome are likely to be inherited together.
What is an autosome?
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
Talk about autosomal linkage?
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-
Talk about sex linkage.
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
What is epistasis (give an example)?
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.
Talk about the chi-Squared Test
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.
Define population
A population is a group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed.
Define gene pool and allelic frequency
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.
What is the Hardy- Weinberg principle?
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.
What do we assume while conducting the hardy- Weinberg principle
- 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
Talk about the allele frequency equation.
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
Talk about the genotype frequency equation
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
Define Variation
This is the differences that exist within individuals. Variation within a species means individuals in a population can show a wide range of phenotypes.
Define Evolution
This is when the frequency of an allele in a population changes overtime. This can occur by genetic drift or natural selection
Talk about Natural Selection
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.
What are the three types of natural selection?
- Stabalising
- Directional
- Disruptive
Talk about stabalising selection.
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.
Talk about Directional Selection
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
Talk about Disruptive selection
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
What is speciation?
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
Talk about Allopatric Speciation
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.
Talk about Sympatric speciation
This occurs when random mutations within a population prevent individuals from mating. It is pretty rare.
What is genetic drift
Instead of environmental factors affecting which individuals survive, breed and pass on their alleles, change dictates which alleles are passed on.
Talk about the process of genetic drift
- 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.
What is an ecosystem
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
What is an ecological niche?
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
What is a carrying capacity?
the maximum stable population size of a species that an ecosystem can support
Talk about Interspecific Competition
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
Talk about Intraspecific Competition
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
What is predation?
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
What does investigating population involve looking at?
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
Talk about quadrats?
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.
Talk about transcets?
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.
Talk about the process of mark- release- recapture.
- capture a sample of species using an appropriate technique and count them.
- Mark them in harmless way by using. an identification tag.
- Release them back.
- Wait a week, then take a second sample from the same population.
- Count how many of the 2nd sample are marked then use the equation to estimate total population size
Talk about assumptions made by mark- release- recapture method.
- 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
What is succession?
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.
What’s the difference between primary and secondary succession?
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.
Talk about the process of succession
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
What is conservation?
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
