1.3 Evolution Flashcards
What is the most accurate definition of biological evolution?
Descent with modification - passing of genes from parent to offspring
Has evolution been observed?
Yes
How do we construct a phylogeny?
Anatomical, genetic, behavioural, fossil, other data
Computer algorithms - find the pattern (phylogeny) that represents the best estimate of evolutionary patterns whilst minimising the assumptions involved (Ockham’s razor of science)
What is a phylogeny?
- diversification of lineages through evolution with modification
- any scale: populations to massive groups
- temporal (changes over millions of years) or just relative sequence
- not about gross similarity (how things look)
- emphasises shared novel traits not primitive traits
What are uses of phylogenies?
- Track pattern of evolution of traits: youngest, oldest, rate of change of traits
- Test for convergent evolution (independent evolution of similar traits)
- Examine correlation of “trait” evolution at any scale e.g., species and continents, hosts and parasites, adapation, and diversification
What is anagenesis?
Gradual transformation (along branches) of one species into another (i.e., rapid extinction of the ancestor)
- linear progression
What is cladogenesis?
Rapid splitting of a species into 2+ parts at nodes
- can be seen through isolation of ancestral groups
- branched progression
What are sources of variation (processes of evolution)?
What kinds of progeny are produced?
- Mutation (quasi-random) - mostly random, some non-randomness
- Recombination (quasi-random), speciation, meiosis (eukaryotes) - pretty random
- Phenotypic plasticity (deterministic) - not random at all i.e., given a certain environment, phenotype relates to that environment, mechanical environment - with increased exertion, bones and muscles change
- Constraints (can reduce or channel variation) - base pairs, mechanical
What are modifiers of variation (processes of evolution)?
What kinds of progeny are in the next generation?
- Natural selection (deterministic)
- Sexual selection (deterministic)
- Genetic drift (quasi-random)
What is an adaptation?
A trait that enhances fitness and that arose historically as a result of natural selection for its current biological role
What does an adaptation require?
- Feature
- More offspring reproducing
- Favoured by natural selection
- Appeared in conjunction with its current function in its environment
What is a key innovation?
Novel trait that originated in a particular lineage, providing evolutionary “advantages” such as increased speciation leading to an adaptive radiation
What is an adaptive radiation?
Explosion of speciation in a lineage, that can be causally linked to its key innovation. Involved ecological and phenotypic diversification
What are some alternative explanations for adaptations?
- Phylogenic constraint/ baggage
- Design constraints prevent the optimal
- Sexual selection - can go against natural selection
- Neutral features (negligible cost to survival)
- Co-variation with other traits - alternative to adaptation - hormones
- Exaptation - a trait originally developed for another function or related to a different environment - later became co-opted for usage for a different function
- Random genetic drift
