M7 Evolution, Speciation and Ecosystems Flashcards
Name the 3 types of selection.
Directional, Stabalising and Disruptive
Describe disruptive selection. Why is it important in the process of evolution?
Mean selected against, both extremes selected for. Could lead to two seperate species.
What is differential reproductive success?
Difference between individuals in a given generation and how many offspring they are able to leave.
Name the two types of speciation. What type of isolation are they?
Sympatric Speciation - reproductive isolation
(same place)
Allopatric Speciation - geographical isolation
What factors cause sympatric speciation?
Ecological - different habitats in same area
Temporal - incompatible breeding seasons
Behavioural - changes in behaviour
Mechanical - incompatible genitalia
Gametic - gametes prevented from meeting (e.g. pollen)
Hybrid sterility
Every Time Bees Make Gametes - Hybrid
How does allopatric speciation occur?
There is genetic variation within any breeding population.
Populations of a species can become isolated stopping GENE FLOW.
New alleles produced by mutation (random).
These seperate populations are subjected to different selection pressures (e.g. enviornment) and so different alleles are beneficial and become more frequent in the population.
Over time GENE POOLS may become so different that if put together once more, individuals can no longer interbreed to produce fertile offspring (new species).
Give examples of selection pressures
- Climate conditions
- Light intensity
- Water availability
- Food availbility
- Disease
- Predation
What is adaptive radiation?
If a population becomes divided and each division is subjected to different selection pressures, their gene pools will diverge so that the phenotypes are adapted to each of the new environments - each may form a different species so that when reintroduced, members of different populations can no longer interbreed successfully.
(Imagine orgininal species radiating out to lots of different new adapted species)
What is genetic drift?
The RANDOM changes in the frequency of alleles in a gene pool - usually small populations.
Smaller populations are more affected by any change in allele frequency (as greater proportion) and so more likely to develop into a new species. They also have lower genetic diversity and as there are fewer alleles, they will have unequal chances of being passed on.
Chance death or migration will also lead to genetic drift.
Any beneficial mutation that is selectively favoured in a small population will rapidly _____ in allele _______ and affect the whole population more _____.
In large populations, the effect of a mutant allele is more _____ and will take _____ to have a significant effect on allele _______.
increase
frequency
quickly
diluted
longer
frequency
Define:
- Ecosystem
- Population
- Community
- Niche
ECOSYSTEM - interacting community of living organisms and their environment
POPULATION - all the organisms of the same species that live in the same place at the same time.
COMMUNITY - all the different populations of different species who live in the same place at the same time and interact with each other.
NICHE - The role of an organism in the ecosystem (e.g. nettle acts as a habitat and carries out photosynthesis, behaviours, where an organisms lives, what is eats, predators…)
Give examples of abiotic factors and how they are measured.
Temperature - thermometer
Light Intensity - light meter
pH of the envionment - pH meter
Moisture content of soil - heat-reweigh (another flashcard)
How do you measure the water content of the soil?
1) Take a soil sample
2) Weigh
3) Heat and reweigh until constant mass reached
4) Loss of mass = moisture content
Give examples of biotic factors.
Competition for resources
Food availability
Predation
Disease
What is the carrying capacity?
The maximum stable population size that a particular environment can support over a long period of time.
What is inter vs intraspecific interaction?
INTER Interactions that occur between populations of different species vs INTRA within the same species/population
Other than predation and food availability, what else can be said to describe population-time graphs for 2 different species?
- Predator numbers are always lower than prey numbers as there must be enough prey to reproduce and feed the predators.
- Predators are generally larger and so take longer to reproduce so population increase is delayed and slower compared to prey.
- Cyclic pattern as populations fluctuate.
What is the main term for niche and name the two subcatagory niches?
Ecological niche:
- Fundamental niche
- Realised niche
What is an ecological niche?
Total of an organism’s use of the resources in its environment.
What is a fundamental niche?
The set of resources a population is theoretically capable of using.
What is a realised niche?
The set of resources a population actually uses.
What is the competitive exclusion principle?
When interspecific competition occurs for the same limited resources (as they have identical niches), one population will use the resources more EFFICIENTLY and gain a REPRODUCTIVE ADVANTAGE that will eventually eliminate the other from the habitat.
What is resource partitioning?
Sympatric species tend to consume slightly different foods or use other resources in slightly different ways, allowing NICHE OVERLAP and therefore coexistence.
What is a gene pool?
The total number of alleles in a population at a specific time.
