Chapter 7 - Evolution and adaptation Flashcards
What are some observations that can be made in a population?
- More offsprings born than ones that actually survive
- Natural variation between individuals of a population
- Offpsrings are similar to their parents because they inherit alleles
What did those observations conclude?
- Variation influences the ability to survive and reproduce viable offspring
- Survival phenotypes are passed down to the next generation
What is the survival advantage?
It increases the individuals fitness as their alleles are passed down to the next generation
What are some survival advantages
- gathering food
- avoid predators
- attracting a mate
- producing offspring
What is natural selection?
The process of increasing the likelihood of survival and reproduction of individuals with specific phenotypes
It works through selective pressures (environmental factors) and different phenotypes
What is natural selection’s effect on allele frequencies?
It increases allele frequencies for phenotypes with high survival advantage.
What is the definition of species?
A group of genetically similar organisms that can interbreed to produce viable or fertile offsprings
What are isolating mechanisms?
Factors that prevent individuals from interbreeding as they separate two or more gene pools.
What is speciation?
It occurs when one population separates to form two new populations that are different enough to no longer produce viable offsprings
often the result of isolating mechanisms that prevent gene flow between populations
What are the two main groups isolating mechanisms can be classified into?
Prezygotic barriers and postzygotic barriers
What are prezygotic barriers?
- stops fertilisation
- prevents mating from happening in the first place
What are some examples of prezygotic barriers?
- Temporal isolation
- Behavioural isolation
- Ecological isolation
- Mechanical incompatibility
- Gametic isolation
What is temporal isolation?
different specific breeding times
What is behavioural isolation?
different courtship patterns for species
What is ecological isolation?
geographical barriers like oceans and mountains
What is mechanical incompatibility?
different reproductive structures
What is gametic isolation?
conditions of the female tact being fatal for the sperm
What is postzygotic barriers?
- does not prevent fertilisation
- prevents the formation of viable offspring
What are the 3 types of postzygotic barriers?
- reduced hybrid viability
- reduce hybrid fertility
- hybrid breakdown
What is reduced hybrid viability?
hybrid offspring do not develop properly
- not born
- does not survive reproductive stage
What is reduced hybrid fertility?
if offspring survives reproductive stage, but cannot produce functional gametes
- infertile and sterile (cannot produce healthy offspring0
What is hybrid breakdown?
if first generation hybrid is fertile, then the second generation offspring does not develop properly
What are the two forms of speciation?
- Allopatric speciation
- Sympatric speciation
Which form of speciation is more common?
Allopatric
What is allopatric speciation?
formation of new species because of genetic isolation caused by a geographical barrier
What are the stages of allopatric speciation?
At least two populations of the same species exist.
The populations are separated by a geographic barrier.
Different mutations arise in the different populations, genetic drift causes different random changes in allele frequencies and differences in selective pressures drives natural selection in different directions.
The two populations become genetically different enough that members could not interbreed to produce viable offspring, even if the populations came into contact.
They are reproductively isolated and classified as two different species.
What is sympatric speciation?
It occurs between populations that live in the same geographical area
Gene flow is still possible
Occurs when gene flow is reduced by factors like habitat differentiation, sexual selection or polyploidy.
What is habitat differentiation?
Subpopulation uses slightly different resources or lives in a specific part of the habitat which is different to the parent population
What is sexual selection?
Differences in mate preferences drive sympatric speciation
What is polyploidy?
Occurs when an individual has more than two copies of every chromosome.
More common in plants than animals
