Evolution and the adapted animal Flashcards
How is phylogeny reconstructed?
- anatomical, genetic, behavioural, fossil, other data
- computer algorithms: find pattern (phylogeny) that represents best estimate of evolutionary patterns
- can’t assume most complicated scenarios before the simplest has been ruled out
What is a phylogeny?
- represents diversification of lineages through evolution
- any scale: populations to massive groups
- temporal or just a relative sequence
- NOT about gross similarity, evolutionary rates vary
- emphasis shared novel traits not primitive ones
Birds developed evolutionarily quite quickly
What use are phylogenics?
- Track pattern of evolution of traits: youngest, oldest, rate of evolution, timing of change
- Test for convergent evolution (independent evolution of similar traits)
- Correction of trait evolution at any scale e.g. species and continents, hosts and parasites, adaption and diversification
What is an adaptation?
Trait that enhances fitness and that arose historically as a result of natural selection for its current biological role
- requires: feature, more offspring reproducing, favoured by natural selection, appeared in conjunction with its current function in it’s environment
What are key innovations?
Novel trait that originated in a particular lineage, providing evolutionary advantages such as increased speciation which leads to adaptive radiation
What is adaptive radiation?
Explosion of speciation in a lineage, that can be causally linked to its key innovation. Involves etological and phenotypic diversification
What are alternative explainations for adaptations?
- phylogenic constraint or baggage
- design constraints prevent the optimal
- sexual selection
- neutral features linked to 1
- Co-variation with other traits
- exaptation - old feature is co-opted for a new function in a new environment
- random genetic drift
What motion do most animals use except mammals and crocodiles?
Living vertebrates primitively use medio-lateral (side to side) motion of their vertebral columns to move correlated with a sprawling posture in tetrapods
How did the earliest vertebrates move?
Body segments organised into myomeres with blocks of muscle separated by myoseptum
Contracted in waved to propel the body forwards
How did aquatic locomotion evolve?
Pectoral then pelvic fins evolved to supplement role of axial column in generating thrust and lift
- both fins gained bony supports that expanded distally in fish closely related to tetrapods
What are specialisations related to a wider activity range in archsaurus?
- Erect posture
- 4-chambered heart
- Parasagittal gait
- Hinge-like joints
- Enlarged pelvis and limb muscles
- Later (1st dinosaurs): Bipedalism
- Endothermy - warm bloodidness
What is vertebral motion?
Dorso-ventrally flexible in the lumbar region
- more erect posture and parasagittal gait
- enlarged pectoral and pelvic girdle
