Chapter 14 - Speciation and Extinction Flashcards
Macroevolution
large complex changes in life
Microevolution
many small changes in a shorter period of time (can lead to macroevolution) ex. mutations, natural selection, genetic drift
Defining a “species”: Carolus Linnaeus
Classfied life based on apperances and made a hierachical system for it
x did not consider evolutionary relationships (Charles Darwin did that)
Defining a “species”: Biological definition
”a population, or group of populations, whose members can interbreed and produce
fertile offspring”
x does not apply to asexual reproducing organisms
x does not apply to extict organisms
x some organisms have to the potential to interbreed in captivity, but do not so in nature
x closely related species can sometimes produce fertile offspring, even though gene pools remain seperate
Reproductive barriers
Mechanisms that prevent organisms from sharing a gene pool; prezygotic or postzygotic
Prezygotic:
Habit isolation: different environments
Temporal isolation: active or fertile at different times
Behavioural isolation: different courtship activites
Mechanical Isolation: parts don’t fit
Gametic isolation: gametes cannot unit
Postzygotic:
Hybrid inviability: can’t reach maturity
Hybrid infertility: sterile offspring
Hybrid breakdown: second generation has reduced fitness
Sympatric speciation
New species arises while living in the same physical area as parent species (same environment/ habitat but different microenvironments)
Common mechanisms is polyploidy in plants: number of set of chromosomes increases (produces cotton)
Parapatric Speciation
Part of the population enters a new habitat alongside the original range (part of population moves right same door; different habitats)
Allopatric speciation
New species forms when a geographical barrier seperates the species and they can’t reproduce anymore
Why is determining the type of speciation difficult?
- the definitions represent points on a continuum
- can’t also detect barriers that are important to animals (vs for humans)
- hard to define geographical barriers needed to seperate two populations (depends how far a species can spread its gametes)
What rate does speciation occur?
Gradualism
Evolution proceed in small incremental changes over many generations
What rate does speciation occur?
Puctuated equilibrium
Brief bursts of rapid speciation occurs between long periods of little change
(*occurs if members of a population inherit key adaption)
Extinction & Impact Theory
When all members of a species dies.
Suggests meteorites or comets crashed to Earth, produced large amounts of soot and dust which blocked the sunlight and triggered extinction in a chain-reaction.
Background extinction rate
Gradual loss of species due to normal evolutionary processes
Mass extinction
Rapid loss of species in a short period of time
What is systematics?
The study of systematics includes taxonomy (the science of classification) and phylogenetics (the study of species relationships)
