Unit 3 Review 8.1 & 8.2
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Natural selection can occur as a result of a variety of biotic and abiotic factors. What are these factors?
• Food supply • Climate • Predators • Choice of mate
What is the definition of selective pressure?
An evolutionary force that causes a particular phenotype to be more favourable in certain environmental conditions.
What are the 3 types of selection?
Directional, Stabilizing and Disruptive
What is Directional selection?
Favours an increase or decrease in the value of a traits resulting in a shift away from the average condition.
What is Stabilizing selection?
The average phenotype in the population is favoured. Ex. Human birth weight Premature babies are less likely to survive Overweight babies – complications for mother and baby
What is Disruptive selection?
Favours the individuals at the extremes of a trait
What is Sexual selection?
Favouring any trait that enhances the mating success of individuals.
(Female Mate Choice) What do female animals typically choose their mate based on?
physical colouration or behaviour (called the “runway effect”)
(Male vs Male Competition) Males have evolved larger body size and other physical attributes such as antlers. These attributes are used for?
Direct competition
2 types of Sexual Selection are?
• Female mate choice • Male vs Male competitions
What are some examples of sexual selection?
• Giraffe Necks ( Necking ) • Birds of paradise mating dance • Blue Footed Booby
What is Genetic drift?
Change in the gene pool of a species due to chance not natural selection Mostly happens to small populations genetic drift doesn’t produce adaptations.
What is the Bottleneck effect?
A type of genetic drift that results in a tiny sample of the population surviving Ex. natural disaster that randomly kills most but not all of a population
What is the Founder effect ?
Is genetic drift that occurs when a small population separates from their original population and establish a new population in a new location
What is speciation?
The formation of a new species
What is a species?
All members of a population that can interbreed to produce offspring
What is the definition of prezygotic mechanism and list all 5 of them?
Mechanisms that prevent mating and fertilization 1.Behavioural 2.Temporal 3.Ecological 4.Mechanical 5. Gametic Isolation
What is Behavioural Isolation?
Different courtship and mating practices ◦ Ex. Frog calls
What is Temporal Isolation?
Breeding at different times of the year ◦ Ex. Spring flowers
What is Ecological (Habitat) Isolation ?
Similar species occupy different habitats ◦ Ex. Mountain vs Eastern bluebird
What is Mechanical Isolation?
Reproductive organs are incompatible ◦ Ex. Unique shape of male and female genitalia
What is Gametic Isolation?
Male gametes are unable to recognize a female egg of a different species ◦ Ex. marine animals and releasing egg cells into open water…
What is the definition of a postzygotic mechanism and list all 3 of them?
prevent maturation and reproduction (mating and fertilization are possible) 1. Zygotic Mortality 2. Hybrid Inviability 3. Hybrid Infertility
What is Zygotic Mortality?
Zygote is unable to develop ◦ Ex. Some species of goats and sheep can mate but the resulting zygote is not viable.