Stage 2 - Evolution

What are the three main points of cell theory?

1. All living organisms consist of cells

2. all cells come from pre-existing cells by cell division

3. cells are the building blocks of life

What is the RNA World Hypothesis?

Hypothesised that RNA is likely the first self-replicating life

What is some evidence that support the RNA World Hypothesis

• experiments have shown that simple organic molecules (sugar, amino acids, lipids) can form in conditions

• lipids can self-organise (hydrophilic/phobic parts allows assembly into primitive cells

• Ribozymes can catalyse simple chemical reactions (can also evolve)

What is the fossil evidence of evolution

fossilised remains of prokaryotic cells have been found that predate the oldest eukaryotic cell

What is endosymbiosis

heterotrophic (mitochondria)/photosynthesis (chloroplasts) prokaryotes are engulfed by larger prokaryotes

What is the evidence that endosymbiosis has occurred

Mitochondria and chloroplasts have own circular DNA, have own ribosomes similar to prokaryotic ribosomes, self replicate similarly to binary fission, and have contrasting inner and outer membranes similar in composition to prokaryotic membranes.

What is a species

Group of organisms with the ability to actually or potentially interbreed to produce fertile offspring

What are the criteria that can be used to define asexually reproducing organisms? Explain them each briefly

Morphology - similarities in physical structure, size, shape for visual identification

Biochemistry - Members have similar DNA sequences, proteins, and metabolic processes, indicating genetic relatedness

Gene pool - members can interbreed to produce fertile offspring, meaning they can exchange genes within same population

What are the pre-zygotic ways for reproductive isolation? Explain them

Temporal - breeding times differ

Behavioural - courtship rituals differ

Mechanical - Physical differences prevent successful mating

Gamete - sperm unable to fertilise the egg of another species

What are the post-zygotic ways for reproductive isolation? Explain them

Hybrid inviability - hybrid fails to develop to reproductive maturity

Hybrid infertility - hybrid is sterile and unable to produce functional gametes

What is DNA-DNA hybridisation

DNA samples from 2 species are hybridised (combined) to examine how closely they complement each other

Step 1 of DNA-DNA hybridisation

DNA samples from 2 species are heated to seperate strands

Step 2 of DNA-DNA hybridisation

Upon mixing and cooling, DNA strands will join due to base complementary

Step 3 of DNA-DNA hybridisation

DNA is then heated to test strengths of bonds

True or false: higher temperatures for DNA-DNA hybridisation = less closely related = less strong bonds

FALSE

What are the pros of using DNA sequencing to compare genomes

the 2 species can be directly compared

What are the pros of using rRNA sequencing to compare genomes

present in all organisms and highly conserved (doesn’t change much overtime)

True or False: There are more extinct species than living

True

What is a gene pool

sum of all gene variations of individuals in a population

What is evolution

change in frequency of alleles in a population over time

What are the driving forces of evolution

natural selection, genetic drift, sexual reproduction

What is the process of natural selection (all three parts)

1. variation exists within a population, some individuals possess favourable alleles that make them better suited to their environment

2. These individuals survive and reproduce, passing on their alleles

3. Individuals without these traits don’t survive and reproduce

4. over generations, frequency of favourable alleles increase

What are some biotic selection pressures

Predators, disease, competition, symbiotic relationships with other organisms

What are some abiotic selection pressures

Rainfall, temperature, nutrient levels, light intensity

What is genetic drift

relative change in frequency of alleles in a population due to chance events such as catastrophes, mutations, and migration

What is the bottle neck effect? Draw it

Population is reduced dramatically, changing the alleles in the population

What is the founder effect? Draw it

small group of individuals moves away from original population

True or false: smaller gene pool = more likely to survive/pass on favourable genes

FALSE

What is speciation

two or more species form from on ancestral species

What is allopatric speciation? Draw it

physical separation of 2 groups from a population with no gene flow

What are the steps of allopatric speciation?

1. geographical isolation means subpopulations of the same species are physically separated with no gene flow

2. Two groups are subject to different selection pressures

3. Natural selection favours certain characteristics in one population and not the other

4. Over time, and through mutations, genetic differences accumulate to the point that the two groups are reproductively isolated and thus seperate species.

What is convergent evolution

unrelated species independently evolve similar features that serve a common function

what is an analogous feature vs a homologous feature

homologous = evolve different

analogous = evolve similar

What is divergent evolution

population is physically separated and slowly evolve independently, accumulating genetic differences leading to a new species forming

What is Adaptive Radiation

Rapid process where a single ancestor rapidly diversifies into multiple new species by adapting to a different specialised ecological roles in the environment

What is ecological succession

changes in the mix or composition of a community in an area over time

What is primary succession

process which previously lifeless ecosystem becomes colonised

What are the steps of primary succession

1. Pioneer species colonise surface

2. Pioneer species alter the environment, making it favourable for other species to survive and reproduce

3. The other species alter the conditions, making it unfavourable for the pioneer species

4. Leads to change in the mix of species over time

5. Eventually a more stable community (climax community) will establish itself

What is secondary succession

Existing community has been cleared by a disturbance that leave soil intact

What are the steps of secondary succession

1. changed/altered conditions favour initial colonisers/pioneers

2. Initial colonies alter their surroundings/environment

3. Environment becomes more suitable for other species and often less suitable for themselves or others/colonisers are not able to survive

What are human activities that affect extinction rates? explain them

Hunting - leads to threatened or extinct species

Introduced species - biological control or recreation can lead to them being better suited for environment than or predation of native species

Habitat destruction - biodiversity of ecosystems can be reduced (leading cause of extinction)

Pollution

Climate change