Upload
theodore-sutton
View
233
Download
0
Embed Size (px)
DESCRIPTION
Reproductive Isolation the inability of a sp. to breed with another results from barriers, either physical (ex mtns) or behavioural (ex. mating dance). sp. do not breed with each other in nature (even if they are capable of it) various types:
Citation preview
Speciation
Macroevolution
SpeciationSpecies: groups that can reproduce with each
other and produce viable offspringSpeciation: origin of a new species leads to greater diversityMacroevolution: origin and extinction of different
species, evolution of new features eg. wings
Reproductive Isolation the inability of a sp. to breed with another results from barriers, either physical (ex mtns) or
behavioural (ex. mating dance). sp. do not breed with each other in nature (even
if they are capable of it) various types:
1. Geographic Isolation Landforms, water, distance to move (or spread repro.
cells) limits reproduction Genetic drift and natural selection work together to
form unique species. For every species that forms, many more perish ex.Harris’s antelope squirrel and white-tailed antelope
squirrel divided by the Grand Canyon
2. Habitat Isolation some species have adapted to a specific
location within an ecosystem. even though contact is possible, preferences
for their habitat prevents it ex. 2 sp of garter snakes live in same area
• 1 sp lives mainly in water, other on land so don’t interact
Other Reproductive BarriersA. Temporal isolation - different breeding seasonsB. Behavioural isolation - different mating
behavioursC. Mechanical isolation - different reproductive
structuresD. Gamete isolation - different sex cellsE. Hybrid inviability - hybrids are not healthy
enough to survive or reproduceF. Hybrid infertility - hybrids born healthy, but are
unable to reproduce
Adaptive Radiation Divergent Evolution organisms arrive in different environment new habitats encourage speciation
Founder effect + natural selection + reproductive isolation = speciation
evolution from a common ancestor results in diverse species adapted to different environments
Convergent Evolution distantly related species living in similar
environments develop similar adaptations face similar selection pressures
North American antelope (left) and African impala antelope (right) appear to be very closely related, but have actually evolved convergently to resemble each other.
Rate of SpeciationGradualism: evolution of a species by gradual accumulation of small
genetic changes over a long period of time Darwin knew geologic changes occurred very slowly,
believed speciation must evolve in same way
Punctuated Equilibrium: changes to a species can occur suddenly, and can be
extensive enough to create a new species in a short period of time
fossil record shows many new species appearing abruptly
both can occur as a result of Natural Selection
Human Activity usually results in a decrease of
biodiversity island ecosystems at risk ex dodo ecosystems affected by human
activity and introduction of invasive species
modern agriculture and fishing