Chap 14 Speciation and Extinction Flashcards
What is a species?
distinct groups of organisms
Who classified species based on appearance?
Linnaeus
What was the naming system Linnaeus used?
combined the broader classification genus with the term species
The biological species concept defines species by what?
reproduction
Modern biologists use the biological species concept to define species based on what?
their ability to interbreed and produce fertile offspring
When do new species form?
when some individuals can no longer interbreed with the rest of the group
What helps define species?
DNA analysis
What do researchers compare when looking at DNA of a species?
the nucleotide sequence of genes that organisms have in common
How much of an organisms DNA must be identical to be considered the same species?
97%
What causes species to diverge?
reproductive barriers
When a subgroup can no longer interbreed and produce fertile offspring what happens?
it is considered a new species
What happens to the subgroups gene pool when it becomes a new species?
it shifts and begins to follow its own independent evolutionary path
What type of reproductive barriers prevent fertilization?
prezygotic
What type of reproductive barriers prevent development of fertile offspring?
postzygotic
What are the types of Prezygotic reproductive barriers?
habitat isolation temporal isolation behavioral isolation mechanical isolation gametic isolation
What is habitat isolation?
different environments (ladybugs feed on different plants)
What is temporal isolation?
active or fertile at different time (field crickets mature at different rates)
What is behavioral isolation?
different courtship activities (frog mating calls differ)
What is mechanical isolation?
mating organs or pollinators are incompatible (sage species use different pollinators)
What is gametic isolation?
gametes cannot unite (sea urchin gametes are incompatible)
What are postzygotic reproductive barriers?
hybrid inviability
hybrid infertility
(sterility)
hybrid breakdown
What is hybrid inviability?
hybrid offspring fail to reach maturity (hybrid eucalyptus seeds and seedlings are not viable)
What is hybrid infertility (sterility)?
hybrid offspring are unable to reproduce (lion-tiger cross /liger/ is infertile)
What is hybrid breakdown?
second-generation hybrid offspring have reduced fitness (offspring of hybrid mosquitos have abnormal genitalia)
What defines two types of speciation?
spatial patterns
Reproductive barriers can arise from what?
physical or nonphysical separation
What are the types of speciation?
Allopatric
Sympatric
What is Allopatric speciation?
when there is no contact between populations (physical barrier)
What is sympatric speciation?
When there is continuous contact between populations (nonphysical barrier)
What can lead to allopatric speciation?
islands (Galapagos tortoise)
What can lead to sympatric speciation?
microenvironments
(in lake large fish feed near shore small fish feed in deeper waters, fish breed where they eat so they don’t mix together and populations started to acquire genetic differences)
Why is it difficult to determine the type of speciation?
nature is usually a continuum, from complete reproductive isolation to continuous intermingling
we may not be able to detect the barriers
a barrier is not necessarily the same for each species
When can speciation occur?
after a mass extinction
What can lead to mass extinctions?
major environmental changes
What happens to organisms that survive a mass extinction event?
they are able to exploit new resources in the changed environment, so they diversify after the others die
When is the sixth mass extinction?
now
Why are current extinction rates accelerating?
human activity
How do humans profoundly alter the environment?
causing habitat loss and fragmentation
creating pollution
introducing nonnative species
overharvesting
What are especially vulnerable areas affected by human activity?
islands
