Lecture 13: Rates and Patterns of Evolution Flashcards
What is evolution?
The change in heritable characteristics of populations over successive generations (the change in frequency of different alleles in a population)
What is microevolution?
Occurs within a population: accumulation of small changes (ex: pesticide resistant insects) observed though genetics
What is macroevolution?
Evolution over geological time (new species occurring) and observed mainly through fossils
What is trait vs taxon?
A trait refers to a specific characteristic of an organism.
A taxon is a group of organisms that are classified together based on shared characteristics
What are examples of morphological, physiological and behavioural traits?
Morphological: organ presence, body size, colour
Physiological: live birth vs eggs, homeo or heterothermy
Behavioral: migration, hibernation, song
T or F: number of genes is a good proxy for complexity
False, some protists have more gens than all mammals
How does complexity change with evolution?
Towards specialization in traits over time
(a species can lose generalized traits to become better adapted to a very specific habitat/niche)
T or F: a species can regain a trat if it is lost through evolution (and why?)
T! Rare but happens (ex: viviparous trait in some lizards reappears after evolving) –> happens because some traits are never gained/lossed, merely expressed or not expressed.
What is a key innovation?
A novel and sudden phenotypic adaptation to one or more ecological niches (ex: flight, hard bodies, seeds)
How are seeds an example of key innovations?
First land plants reproduced mainly by spores –> Development of seeds allowed plants to reproduce away from water and experience dormancy –> Allowed greater provisioning and dispersal –> Vast majority of plants now reproduce by seed
What is the Island (Fosters) rule?
Species that evolve on islands typically get either larger or smaller than their mainland counterparts.
What is insular dwarfism?
animals which are large on the mainland become smaller on islands due to
limited resources and the fact that large sizes aren’t selected for since there are fewer predators and fewer large prey.
What is insular gigantism?
Species which are small on the mainland,
tend to become large on islands because the lack of large carnivores gives rise to empty niches filled by growing carnivores and the fact that small herbivores can escape predation but no predators means they can grow larger
How do molecular clocks date evolution?
For extant species: The background rate of mutation, often of ‘invisible’ mutations –> more similar = more recent divergence
What is “creeps versus jerks”?
Gradual processes over time is creeps
Sudden abrupt changes is jerks
evolution is gradual and “creeps forward”
What is gradual speciation vs punctuated equilibrium?
Gradual speciation involves many evolutionary steps between an ancestral species/trait and a current species/trait
A punctuated equilibrium is a chance mutation that causes a sudden speciation
Is Gradual Speciation or Punctuated Equilibrium more likely?
Gradual is more likely since fossil records suggest it but sometimes punctuated equilibrium does happen (ex: salamander vs axolotl)
What is a living fossil?
Some species in the fossil record follow punctuated equilibrium and are still recognisable in the living organism many years later
What is Irreducible complexity?
Trait(s) whose function(s) have become so essential to life, losing them through evolution seems impossible.
