Natural selection Flashcards
(34 cards)
Traits that are similar to ancestry are called ?
Homologies
What is essential for evolution by natural selection
Genetic variation
When does natural selection
Occur?
When organisms vary in genetically controlled heritable traits that alter fitness.
What are alleles
Alternative forms of genes
What is the result of natural selection?
differential survival and reproduction of individuals due to differences in phenotype
What does mutation do in a population
Creates variation Unfavourable alleles select against Successful organisms reproduce Favourable alleles inherited Favourable alleles increase
What is fitness
Fitness is really about how many genes ares passed on
To the next generation
Fitness is a combination of
Survival
Mating success
Number of offsprings per mating
What are the 3types of natural
Selection?
Directional
Stabilise
Disruptive
Name two other types of selection
Artificial selection
Sexual selection
What are the 3 conditions of
Biological species concept
Interbreed in nature.
2. Produce viable and fertile offspring.
3. But do not produce viable offspring with
other species.
If organisms from two sexually reproducing populations do not fulfill these three criteria
What are they called?
Reproductive isolation
What does reproductive isolation do
- Drives speciation
2. Maintains the integrity of a species by reducing gene flow between related species
Give an example of
Behavioural avoidance
These frog species do not recognise each other’s mating calls and this reduces interbreeding where their ranges overlap
What is gametic isolation and
An example
Release their gametes into the water
•But eggs and sperm of different species will not fuse • Because they have different proteins.
Example : sea urchins
Describe Temporal isolation:
Same pollinator
•Flower at different times
•Reduces the chance of pollination from the other species.
When would biological species
Concept will not work?
• Asexual species (bacteria and marine algae) • Parthenogenetic species (unfertilised eggs –
bees, fish)
• Species that mate anyway (eucalypts)
• Fossil species (dinosaurs
Name 3 other species concept
Morphological SC
phylogenetic Sc
Ecological sc
What is allopathic speciation
A population forming a new species while being geographically isolated from the parent population
Sympatric speciation
A subset of the population form new species without geographic separation
How can reproductive barriers leading to sympatric speciation occur when the likelihood of gene flow is high?
- Polyploidy: errors during cell division- extra set of chromosomes. (common in plants- 80%)
- Sexual selection/mate choice: leads to assortative mating. i.e. large with large hermaphroditic land snails
- Habitat differentiation: large geographic range with geographic differences.
Autopolyploidy
Mechanism speciation of plants
Allopolyploidy
Speciation when different species interbreed
Instances that are Allopolyploidy
Asexual reproduction in plant (bulbs) • Self-fertilization • Backcrossing with parent species can restore fertility • Common in crop plants
