Evolution through Natural Selection Flashcards
Define natural selection
The process fo life forms with traits that enable them to adapt to specific environmental pressures will tend to survive and reproduce in greater numbers of their kind.
What are the three observations of natural selection
- Variation
- Birth rate
- Natures balance
Describe observation one - variation
All members of a species show variation.
Describe observation two - birth rate
Is always far greater than the availability of resources would allow.
Describe observation three - natures balance
Despite a high birth rate population numbers stay fairly constant.
What are the two interpretations Charles Darwin demonstrated
- struggle for survival
- survival of the fittest
Describe interpretation one - struggle for survival
Due to excessive birth rate and limited resources.
Describe interpretation two - survival of the fittest
Because there is variation within the species, those with the characteristics best suited for survival are the ones that survive, reproduce and pass on those characteristics.
What is microevolution
Changes of allele frequencies within a species or population over a short period of time
What is macroevolution
Major evolutionary change, especially with regard to the evolution of whole taxonomic groups over long periods of time through the accumulation of microevolutionary change.
What is an example of microevolution
Bacteria
What is an example of macroevolution
Evolution of Horses
Define evolution
Evolution is a change in the allele frequencies of biological populations over successive generations.
How is a variation created/occurs
Mutations
How is variation increased
Sexual reproduction
How does natural selection lead to evolution?
- Variation in population
- More individuals produced can be supported by the environment
- Struggle for survival (competition for resources)
- Individuals with favourable genetic characteristics outcompete individuals lacking favourable characteristics
- Favours individuals survive
- Survivors have offspring
- Desirable alleles passed onto offspring
- Increase in favoured allele in the gene pool
What are 3 adaptations that occur over time
- Environments change over time
- Favourable characteristics therefore also change
- This causes the gene pool to change and the population to evolve.
Define what selection pressures are
Selection pressures are any feature of the environment that reduces or increases the fitness of a particular phenotype in a population of organisms.
What are three forms of selection pressures
- Resource availability
- Environmental conditions
- Biological factors
Describe resource availability as a selection pressure
Refer to the presence of sufficient food, habitat and mates
Describe environmental conditions as a selection pressure
Refer to temperature, weather conditions or geographical access
Describe biological factors
Refer to predators and pathogens
What are the three different types of natural selection
- Stabilising selection
- Directional selection
- Distributive selection
What is stabilising selection
When selection pressures are not changing and the optimal trait becomes more common.
What is directional selection
When changing selection pressures leads to changing traits overtime.
What is disruptive selection
A selection that favours extremes of phenotype range.
Draw a graph/diagram demonstrating a stabilising selection
Check book
Draw a graph/diagram demonstrating a directional selection
Check book
Draw a graph/diagram demonstrating a disruptive selection
Check book
