Process of Evolution (9.2) Flashcards
Describe evolution
Change in genetic composition of populations over time
State how evolution can be observed
Changes in allele frequencies in a population over time
State what is the driving force of evolution
Natural selection
State what natural selection causes
Changes in allele frequencies within a population
State whether or not individuals evolve
No. Only populations or species
State whether mutations in an individual serve as evidence of evolution
No. Only changes in the overall gene pool
Describe species
Group of genetically similar individuals that can produce fertile & viable offspring when interbreeding
Describe the 2 classifications of genetic isolation causing mechanisms
- prezygotic
2. postzygotic
Describe prezygotic isolating mechanisms
Those that typically prevent individuals from different populations from interbreeding
State whether or not prezygotic isolating mechanisms prevent fertilisation from occuring
Yes.
State what prezygotic isolation mechanisms commonly prevent
Mating
List the 6 prezygotic isolating mechanisms
- geographical isolation
- ecological isolation
- temporal isolation
- behavioural isolation
- morphological isolation
- gamete mortality
Describe geographical isolation as a prezygotic mechanism
Populations are separated by physical and geographical barriers (e.g. oceans)
Describe ecological isolation as a prezygotic mechanism
Populations occupy different niches within the same ecosystem
Describe niches
Role/place in ecosystem
Describe temporal isolation as a prezygotic mechanism
The breeding cycles or active times of populations do not overlap
Describe behavioural isolation as a prezygotic mechanism
This occurs when mating calls and courtship ritual are highly specific (only possible in animals)
Describe morphological isolation as a prezygotic mechanism
The reproductive organs of different species are physically incompatible and prevent individuals from mating
Describe gamete mortality as a prezygotic mechanism
Egg and sperm fail to fuse in fertilisation
Describe sexual selection
The difference in the ability of individuals to acquire mates
Describe the effect of sexual selection on evolution
Increase the likelihood of ‘fitter’ alleles being inherited by the next generation and the presence of favourable alleles in the gene pool
Describe postzygotic isolating mechanisms
Those that typically prevent a zygote of two different species from developing into a fertile adult
State what the offspring resulting from interbreeding between individuals from different species are called
Hybrids
Describe hybrid inviability
Reproductive isolation - sperm from one species fertilises egg of another species to form hybrid zygote (but unmatched chromosomes prevent embryonic development)
Describe reduced hybrid viability
Postzygotic isolation - offspring of different species survive to birth/germination but do not reach reproductive maturity
Describe hybrid sterility
Postzygotic isolation - hybrid offspring are reproductively mature but incapable of reproducing
State what hybrid sterility is usually a result of
Problems encountered during gamete formation
Provide 1 example of a hybrid
Mule
State whether or not hybrids have homologous chromosomes
No
State why hybrids do not have homologous chromosomes
Genetic material comes from different species
Describe hybrid breakdown
Postzygotic isolation - first-generation hybrid cannot reliably produce viable second-generation offspring when interbred with other hybrids
Describe endemic
Native species
Describe speciation
Evolution of new species from an ancestral species
State what the most common form of speciation is
Allopatric speciation
Describe allopatric speciation
Divergent evolution of two new species from an ancestral species resulting from separation by a geographical barrier
State when allopatric speciation occurs
When a population becomes divided by a geographical barrier
State what spatial isolation prevent individuals of separated sub-populations from doing
Interbreeding
Describe niche
A role assumed by a particular organism within its’ community
What name is given to the process in which one species evolves to closely resemble another?
Mimicry
Describe gene pool
All alleles possessed by members of a population, which may potentially be passed to next generation.
Describe the relationship between gene pool and genetic diversity
A gene pool is the total genetic diversity found within a population or a species.
Describe the relationship between large gene pool and genetic diversity
Large gene pool that has great genetic diversity.
Describe adaptive radiation
Process in which organisms diversify rapidly from ancestral species
State what low heterozygous presence in a population indicates
Low genetic diversity
Describe how a mass extinction results in new species evolving
Reduces competition for resources and leaves many vacant niches, which surviving lineages can evolve into.
Describe transitional fossils
Any fossil that exhibits traits common to both an ancestral group and its derived descendant group.
