Chapter 18 + 19 - Populations And Evolution, Populations In Ecosystems Flashcards
What is a species
Organisms that can reproduce to produce fertile offspring
What is a population
All of the organisms of a single species in one place at one time
What is a community
All the organisms of all the species in one place at one time
What is a gene pool
All the alleles present in a population
What is allele frequency
How common an allele is in the population
What is meant by evolution
A change in allele frequency over time
What’s meant by differential reproductive success
Organisms with a phenotype better adapted to their environment have a selective advantage and are more likely to survive and reproduce and vice versa
What is meant by speciation
The process of forming a new species
What is the purpose of the Hardy-Weinberg principle
Predicts the frequency of alleles, genotypes and phenotypes in a population
What does the Hardy-Weinberg principle predict
The frequency of alleles of a gene will stay constant over generations
What are the assumptions of the Hardy-Weinberg principle
- No mutations
- No selection
- Random mating
- Large population (no genetic drift)
- Population is genetically isolated
- No migration between populations
What is the equation for the Hardy-Weinberg principle
P + q = 1
P = All dominant alleles
Q = All recessive alleles
If you know the frequency of one allele you can find the frequency of the other
p^2 + 2pq + q^2 = 1
P^2 = Homozygous dominant
2pq = Heterozygous
q^2 = Homozygous recessive
Research Hardy-Weinberg to understand it
Research
What is infraspecific variation
Individuals of the same species have the same genes but different alleles
There is variation in their phenotypes
What is interspecific variation
Individuals of different species have different genes and and live in different environments
What is continuous variation
Variation is not discrete so can not be set into specific categories
Represented on a line graph
Eg height
What is discontinuous variation
Individuals fall into discrete groups with no intermediates
Represented on a bar chart
Eg blood group
What are the causes of variation
Genetic - Mutation - Meiosis (crossing over and independent segregation) - Random fertilisation - Inherited by next generation Environmental - Environment can influence phenotype - Can change over lifetime eg accent Most variation is likely to be as a result of both eg height due to genetics and childhood nutrition
What is speciation
The process of forming a new species
- Populations becomes reproductively isolated
- There can be no gene flow between them
What is meant by allopatric speciation
- Geographical isolation resulting in reproductive isolation
What is meant by sympathetic speciation
Speciation occurs when species are not geographically isolated or reproductively isolated, therefore can be:
Morphological - anatomy
Seasonal - reproductive at different times of years
Explain how speciation occurs
- Variation exists in population due to mutations and environmental differences
- Different selection pressures eg environmental conditions, courtship behaviour
- Directional selection of different phenotypes
- Differential reproductive success
- Causes a change in allele frequency over many generations
What is meant by genetic drift
When there is a change in allele frequency between generations due to random chance
What are some characteristics of genetic drift
- It affects small populations much more than large populations
- Changes the allele frequency so is a cause of evolution
- Does not depend on the environment
Explain directional selection
- A change in environmental conditions
- Individuals with an extreme type of characteristic are more likely to survive and reproduce
- Parent population is exposed to antibiotic
- Only those with allele for resistance will survive and reproduce
- Antibiotic resistance allele will increase in offspring
- The mean amount of antibiotic resistance changes
Draw the graph for directional selection
In folder
Explain stabilising selection
- Individuals with extreme types of characteristic are less likely to survive and reproduce
- Most extreme likely to die
- Most likely to survive in middle range
- Means remains the same
Draw the graph showing stabilising selection
Folder
What is meant by disruptive selection
When both extremes of the phenotype are more likely to survive and reproduce than the mean phenotype
The environment selects for 2 separate phenotypes
Contribute to sympathetic speciation
Draw the graph showing disruptive selection
In folder
What is an example of disruptive selection
Environment = black rocks and white rocks
White and black rabbits survive due to camouflage
Intermediates don’t survive
What is meant by abundance
The number of individuals of a single species in an ecosystem/habitats (population size)
What is meant by distribution
Where a species is found in an ecosystem/habitat
What is meant by infraspecific competition
Competition within a species
- occupy the same niche
- Compete for everything such as food and mates
What is meant by carrying capacity
The maximum stable population an ecosystem can support
Draw a graph showing carrying capacity and population
In folder
Why does carrying capacity vary
Due to biotic and abiotic factors that are limiting factors
What are examples of biotic and abiotic factors that can act as limiting factors to a carrying capacity
Biotic - competition for food
Abiotic - Nesting sites
Draw a graph showing predator-prey relationship
In folder
What is meant by interspecific competition
Competition between species
- The abundance of one species will affect the other
- Species with a similar niche will compete for resources
What is meant by a niche
The role that an organism plays in an ecosystem
What are examples of biotic factors that make up a niche
- Interspecific competition for resources
- What it eats
- What eats it
What abiotic factors make up a niche
- Shade
- The availability of gases it uses
- Absorption if nitrates
- Where it lives
- Temperature
Explain why each species has its own niche
- If 2 species had exactly the same niche they would compete for everything
- Species can have similar niches, known as a niche overlap
- Causes interspecific competition
What will the abundance of a species depend on in an ecosystem
How much competition for resources exists
What will the distribution of a species depend on in an organism
Where it’s niche exists
What are transects and quadrants used to survey
Immobile or slow moving organisms eg plants
What type of sampling are transects used for
Systematic
What is the purpose of systematic sampling
Records the distribution of the organisms/species changing in a line
Eg between high and low tide
Explain the process of line transects
- Run a tape measure between 2 points
- Record all of the species on that line
Explain the process of belt transects
- Using quadrants along three length of the transect
What type of sampling are quadrants used for
Random sampling
What is the purpose of random sampling
Records the abundance of species in an area
What is the purpose of sampling
- Impossible to count all organisms
- Samples have to be representative of the whole ecosystem
- Sample data can be used to estimate the total number of individuals in an ecosystem
Explain random sampling
- Divide sampling area into a grid
- Number squares
- Use random number generator to choose coordinates
- Avoids bias
Explain and give an example of non-random sampling
Systematic sampling
Samples taken at fixed intervals
How does the number of samples influence data
- Can be more representative of population
- Larger number is more reliable
- Too many is a waste of time and resources
- Need enough data to carry out statistical test
- calculate a running mean, stop when mean levels out
What is the purpose of mark-release-recapture
Used to estimate the abundance of a mobile species eg fish or rabbits
Explain the method for mark-release-recapture
- Capture organisms using appropriate method
- Make them in a way that doesn’t harm them (doesn’t effect their ability to mate, doesn’t increase their chance of predation)
- Wait (long enough for them to redistribute amongst population, not too long so that births/deaths and immigration/emigration take place
- Capture second sample
- Use equation
Explain the process of interrupted transect
- Using quadrants at fixed intervals along the transect
What is meant by succession
A series of changes in a species composition in a given place over time
What is meant by climax community
The final stage of succession, where few species dominate and there is a stable equilibrium of species
Draw a diagram and explain the process of succession
- Area is colonised by pioneer species
- This makes the environment less hostile eg due to increase in nutrients like phosphate
- This allows other species to out-compete preceding species
- This continues until climax community is reached eg woodland
What factors increase as succession take place
Soil depth Water and nutrient availability Biodiversity Plant height Niches
What factor decreases as succession takes place
Light intensity near the ground
What are the three types of succession
Primary
Secondary
Deflected
Explain primary succession
- Starts from newly formed land with no soil
- Harsh abiotic conditions
- Very slow to climax
Explain secondary succession
- Starts from land where vegetation has been cleared eg deforestation, fire
- Less harsh abiotic conditions (more soil etc)
- Much faster to climax
- Pioneer species can be larger
What is meant by deflected succession
A community that remains stable because human activity prevents natural succession from taking place eg mowing and grazing
Explain what happens when deflected succession takes place
- Succession stops as plants can’t grow
- Therefore can’t be outcompeted
- Grassland becomes climax community
Why are not all climax communities the same
Different ecosystems have different abiotic conditions so develop into different climax communities
What is the formula to work out total population from mark-release-recapture
Total no. of individuals caught in 1st sample x total no. In 2nd sample / no. of make in 2nd sample
