9/20 quiz vocab Flashcards
endangered species example
Florida panther
caused by: poaching, vehicle collisions, habitat loss, and fragmentation
extinction vortex
cycle of factors worsening extinction status
in extinction, drift can increase…
inbreeding load
can increase the frequency of deleterious alleles
example of morphological sign of inbreeding
kinked tails in florida panthers
88% had them in florida, only 9% in other cougar species
what does increase in genetic variation allow for?
better survival of the species
can better withstand disease or deleterious alleles
what mechanisms of evolution did cheetahs experience?
genetic drift, bottleneck, and inbreeding
allopatry
different geographic locations
sympatry
same geographic location
biological species concept
species are groups of interbreeding natural populations (not domesticated or captured) that are reproductively isolated from other such groups
what is the biological species concept largely based on?
reproductive isolation!
limitations of biological species concept
1) problematic for species that can’t feasibly be tested for reproductive isolation (spatial/temporal differences)
2) issues with getting species to mate in artificial conditions
3) hybridization is more common than we think
steps of speciation
1) genetic isolation
2) divergence of traits accumulate
3) reproductive isolation
vicariance
physical barrier causing dispersal
geological events
river formation, mountain ranges rising, continental drift
example of vicariance by climate change
Pleistocene period
cycle of glacial and interglacial periods that can lead to refugia and separate populations
refugium
places that isolated populations of once widespread species survive major environmental changes
species that experienced speciation by climate change vicariance
toucanets
found glacial period refugia in separating forest canopies, but as they disconnected the species behaviorally wouldn’t fly to other areas and they speciated
continental drift
movement of landmasses on the earth’s surface
consequences of continental drift on ecological systems
creates and breaks down barriers for dispersal
weather impacted as positioning of continents and major oceans influences weather patterns
examples of vicariance by continental drift
pangaea (one large)
->
gondwana and laurasia (two regions)
->
n/s america, africa, asia, antarctica (5 regions)
population impacted by continental drift for speciation
ratites - type of flightless bird
hypothesized they lived together in gondwana but as it fragmented, they were split apart and then speciated
genetic isolation can occur by…
physical barriers (vicariance), dispersal, or genetic barriers
dispersal example
islands or “sky islands”
what are sky islands
mountain tops for alpine species with extreme arid climate in valleys between
species don’t behaviorally move from mountain top to mountain top because of these climate differences
examples of genetic barriers to disperal
polyploidy, major chromosomal changes, other genetic changes
genetic barrier to dispersal meaning
egg and sperm can’t fertilize each other
polyploidy problem
incompatible amounts of chromosomes
example of genetic isolation by genetic barrier
tree frogs
Hyla versicolor = tertaploidy, H. chrysosceli = diploid
versicolor likely originated from chrysoscelia genome duplication
morphologically identical but different mating calls
diverge
accumulation of differences from each other (when populations have separated)
what can cause mutations to become fixed/lost in different populations?
selection and/or genetic drift
many species ____ reach full reproductive isolation
DON’T
hybridization can happen more often than we may think
what are the classifications of isolating barriers?
premating, postmating prezygotic, postzygotic
what are premating barriers?
prevention of transfer of gametes
what are postmating prezygotic barriers?
mating occurs, but zygote doesn’t form
examples of prezygotic barriers
ecological (temporal, habitat, etc. prevent mates from meeting)
sexual isolation or pollinator isolation (can meet, but don’t ex: different mating calls or female not attracted to male)
what is temporal isolation?
periods of reproduction or emergence aren’t compatible
think cicadas in 13/17 yr cycles
what is habitat isolation?
species occupy different habitats in same geographic region
think ladybugs feeding and mating on different species of plants
what are postzygotic barriers?
mating occurs, and zygote forms but hybrids have lowered fitness
examples of postzygotic barriers
heliconius butterflies - hybrids have lower fitness because they don’t have appearance that camouflages them as poisonous species like parental species do (example of positive frequency-dependent selection, parents surviving bc of majority phenotype)
chorthipus grasshoppers - hybrids aren’t as successful at attracting males bc of unique mating call
what are the two models of speciation?
allopatric and sympatric
what is allopatric speciation
speciation in non-overlapping regions
more common
1) physical barrier, 2) no gene flow, 3) genetic differentiation
what is sympatric speciation?
speciation in overlapping regions
1) temporal/seasonal/ecological barrier, 2) individuals can still come in contact and there can be significant gene flow, 3) significant genetic differentiation
reminder about speciation
species ranges are subject to change, can be sympatric at one time and then allopatric at another
example of sympatric speciation
soapberry bugs
adaptation to different beak lengths because of introduction of nonnative plant (smaller fruit)
example of temporal isolation for sympatric isolation
palms of Lord Howe Island
early flowering couldn’t transfer pollen to later flowering ones
convergent evolution
organisms evolving to have similar traits because adapting to similar environments
not necessarily recent common ancestor
example of convergent evolution
sugar glider (oceania) and flying squirrel (north/central america)
what is phylogeny
evolutionary history of a group
what does a phylogeny tree do?
summarize evolutionary history
can depict timing and pattern of branching events
most closely related species should have the most traits in common
nodes can also rotate and maintain same idea
choose parsimonious tree
this will minimize the amount of evolutionary change, keep it simple!
keep in mind, phylogenies are ___
hypotheses
based on data we have
Homo sapiens are the ___ ___ of an otherwise extinct group of species
lone survivor
how long ago did human and chimp lineages diverge?
about 6-7 million years ago
what preceded H. sapiens?
several other species of hominin
what does hominin means?
any species more closely related to human than chimpanzee
how are H sapiens and chimps different?
H: fully upright posture, relatively hairless, smaller incisors, fully opposable thumbs, larger brain size for language, recognition of complex cause and effect, development of complex culture
what is not so special about humans?
technology/tool use
innovation
communication
cultural inheritance (evolution of a culture over time)
anatomic differences between chimps and humans
1) flat face
2) long legs, short arms
3) very different pelvis shape
4) anterior foramen magnum (head is more central on spine, not sitting in forward posture)
5) s-shaped spine
6) curved feet
what are all anatomical differences adaptations for?
bipedalism
what is a trade off for our bipedalism traits?
terrible childbirth
a lot of complications and death
additional differences between humans and chimps
extremely fine motor control (hand, lips, tongue, oral cavity)
opposable thumbs, shorter fingers
descended larynx (tradeoff: choking)
costs of humans having larger brains
higher metabolic rate relative to fat-free body mass than chimps, gorillas, and orangutans
what’s an important consideration when forming a phylogenetic tree other than appearance?
geography
benefits of humans having larger brains
social brain hypothesis: living in large social groups could have resulted in natural selection that favored larger brains
bigger groups are more successful because of cooperation and accumulated and transmitted knowledge
we need big brains for language to maintain those large groups’ organization
what does radiation mean?
the rapid evolution of multiple species from a single ancestor
why do we not have a great understanding of human evolution?
we have a lot of incomplete skeletons because hominin bodies are terrible at fossilization, which is what we base a lot of ancestry info on
there’s also a lot of closely related lineages, leading to a lot of uncertainty
what are some limitations of fossil records?
we don’t know when hominins lost body hair or started to wear clothing
lice
are highly specialized blood sucking parasites that live on a single host species
a lot of ape relatives have one species, humans have three
co-speciation hypothesis
two sets of two species diverge at the same time
in terms of humans and chimps, their lice diverged at the same time as them (6-7 mya)
