Evolution Flashcards
For selection to be possible, what must exist?
Natural variation
What is biological evolution
Heritable change of a population over time
2 types of evolution an explain each of them
1) micro evolution: changes in one or few genes (no new species)
2) macroevolution : formation of new species
What does Lamarck state?
-changes in the environment cause organisms to evolve
- patents can pass on acquired traits (phenotype)
What is epigenetics?
How environment and behaviour affects gene expression without altering genetic coding of an organism.
Artificial selection
To breed desirable, heritable characteristics
What does Darwin state?
Natural selection is the driving force of evolution
What is natural selection?
An individual with more favourable traits is more likely to survive and reproduce.
What are the 4 of Darwin’s observations?
1) in one species there is a great (phenotypic) diversity
2) organisms produce more offsprings that can survive.
3) there is a struggle to survive
4)Differential reproductive success : individuals with favourable traits is more likely to reproduce (more)
Theory of evolution does not attempt to….
Explain how life on earth began
Natural selection includes:
1) biotic and abiotic pressure
2) sexual selection
Adaptations
1) explain
2) when and how does it occur?
1) ability of a specie to survive in a specific environment
2)occurs at population level , can also be behavioural, morphological, or physiological, selected by environment
Key points of theory of evolution:
1) species evolve over time
2)new species arise from the evolution of an ancestral species (macro evolution)
3)all living organisms originated from a common ancestor
How to know if organisms evolved from each other?
-change in population (genetics)
- formation of new species
One example of micro evolution:
Dogs (artificial selection of dogs = same species)
Macroevolution
- new species, new genus, new family
Limitations of fossils
-Fossil record is incomplete (fossils rarely form)
-info about external, not internal
- evolution can occur without morphological changes (ex: height and diet)
Phylogenetic tree
-fossil records
- hypotheses about macroevolution
Biogeography
-Study of geographic distribution of organisms
-Examines the patterns where organisms live on earth
Continental drift
Similar organisms found on different continents: descend from a common ancestor that lived before the continents drifted.
Comparative anatomy:
1) homologous features (divergent evolution): organisms with similar structures but different functions (hypothesized to have a common ancestor)
2) vestigial structures: original function lost as species adapt to different modes of life.
What are analogous structures?
Organisms with separate ancestries adapt in similar ways due to environmental demands
What is convergent evolution?
Evolution of similar or analogous features in distantly related groups.
Post Darwin ideas
- molecular homologies:
- the more recent the common ancestor, the more sequence similarities (DNA and /or amino acid sequence of proteins)
- leads to a revision of evolutionary trees
Limitations of evolutionary trees
-assumption that genes are passed only vertically
- conserved sequence
- hybridization of species can occur
Factors leading to evolution
When one of the five conditions of h-w is not met
Adaptive
Natural selection
Non-adaptive
-non random mating that is not adaptive (interbreeding=reduce genetic variation)
- genetic mutation
-genetic drift: bottleneck, founder effect
- gene flow
Fitness
Ability to produce a surviving offspring
Natural selection causes changes in ?
Allele frequency
3 modes of selection of phenotypes:
1) stabilizing : favours intermediate variants
2) Directional: favours one phenotypic extreme
3)Disruptive :favours individuals on both extremes
Sexual selection: non random mating= natural selection can lead to….
-can lead to stabilizing, directional or disruptive selection
According to evolutionary theory, what had to be the source of all original variation?
Mutation (theory hypothesize a single ancestor)
Bottle-neck genetic drift:
sudden decrease in population size➡️ reduction in genetic diversity
Founder effect genetic drift
Individuals leave the population and starts a new population: founders has less genetic variation that original, population )
What kind of population is more susceptible to genetic drift? Why?
Small populations, because allele frequencies are are likely to change by random fluctuations
Gene flow
-Transfer of alleles between populations of same or different species
-result of mvmt of fertile individual or gamete
- if between different species➡️ horizontal gene transfer
Geneflow
What are the 5 condition of H-W
-no random mating
-no natural selection
-no mutation
-No gene flow
- no genetic drift
How new species arises? Explain
1) allopathic speciation :
-habitat isolation occurs: prezygotic reproductive barrier b/w groups
-each population exposed to different selective pressures, genetic drift, +/or mutation that cause macroevolution.
-eventually 1/ both populations undergo genetic changes that results in the formation of permanent reproductive barriers
2) sympatric speciation
- same place
- in geographically overlapping populations
- occurs if gene flow is reduced by mutation, habitat differentiation or polyploidy)
- result of changes in development
3) hybrid speciation
How polypoidy arises in plants
1) Autoploidy (no hybrid formed)
2)Allopolyploidy (hybrids)
What is autoploid?
Individual with more than 2 chromosome sets derivespd from a single species
How are phylogenetic trees constructed
Presence of common structures
Fossils records
Molecular analysis
What is a gene pool
All alleles present in a population
Change in gene pool suggests…
Macroevolution
In microevolution…
Selective pressure act on individuals
5 conditions that must NOT be met for evolution to occur
- No natural selection
- Random mating
3 no net mutations
4.Large populations
5.No migration b/w populations
Sexual selection
-non random mating that is an example of Natural selection
1) direct competition
2)indirect competition
Genetic mutations are random or not?
When can they be passed to offsprings?
Yes, random.
When they are in gametes
What is quicker : sexual or asexual reproduction? Why?
Sexual. It is a rapid combination of alleles while asexual is dependent on mutation to generate new alleles.
