Evolution Flashcards
3 groups of living mammals distinguished by their reproductive biology
- monotremes
- marsupials
- eutherians
who are the closest living relatives of humans?
chimpanzees and bonobos
who are the hominids?
evolutionary lineage leading to modern humans
what is the only homonin thats not extinct?
homo sapiens
a key trait that evolved in the common ancestor of hominins is:
bipedal locomotion
advantages to bipedal locomotion
- forelimbs free to manipulate and carry objects
- eyes elevated, look for prey/ watch for predators more effectively
- move over long distances more energetically efficiently than close relatives with quadrupedal locomotion
early hominins: Australopithecus
- “lucy” most complete australopith skeleton, found in Ethiopia
- had relatively small brains, elongate faces, and a bipedal gait
- 2 lines of evidence
- pelvis and foot morphology
- laetoli footprints
homo
- homo clade diverged from an australopithecine ancestor
- genus homo have larger brains, less elongated faces than earlier hominin ancestors and a bipedal gait
earliest known species of homo clade
homo habilis
-first evidence of tool manufacture
habilis
handy man
homo erectus
- large skull, relatively long legs and short and straight fingers
- traits suggest they were bipedal and primarily terrestrial (not in trees)
- made more complex tools than homo habilis
- able to control fire
who was the first hominid to leave africa?
homo erectus
-fossils found in europe, india, china, and indonesia
homo neanderthalensis
-common ancestor had increased brain size, decreased jaw muscles
-indicating a shift in diet from herbivory to omnivory
-increased brain size may reflect increasingly complex social interactions and cultural traditions
-stocky with a large skull/brain
-advanced tool technology
hunters of large animals, cave dwelling
who was the hominin not found in Africa?
- homo neandethalensis
- widespread in asia and Europe
how do we know that neanderthalensis practiced symbolically?
-flower burial at Shanidar cave, Iraq
homo sapiens
- evolved in Africa
- large brain, slighter build
- early humans overlapped with heir sister species neanderthalensis
- made sophisticated tools and art
- paintings and sculpture
- homo spies spread across all of asia reaching north america
did early humans and neanderthalensis interbreed?
- yes
- descendants of eruopeans, asians, other non africans inherited 2% of their genes from neanderthals
- genetic analysis also suggests blonde/ red hair, fair skin and thick body hair may be inherited from neanderthals
biological evolution
theory that all organisms on earth are related and have changed over time from an original ancestral form
what is modified?
the frequency of particular genes (alleles) within a population
Where are genes located?
on chromosomes
different versions of a gene are called
alleles
the result from evolution
genomes of species differ from those of their ancestors
how do populations evolve?
populations evolve when the environment favors some treats over others, then alleles that code for those traits increase in frequency over time
human example of evolution
the red blood cell production in tibet
- tibetans who live at very high altitude, derived from chinese ancestors who lived at low altitude
- most humans respond to low oxygen at altitude by making more red blood cells to carry more oxygen
- good in short term
- tibetans have big frequency of an allele leading to production of fewer red blood cells in response to low oxygen
- results in more optimal balance of anaerobic vs aerobic metabolism in cells at high altitude
is evolution a theory or a fact?
both!
- theory of evolution deals with how evolution happens
- its also a fact as there is a huge amount of indisputable evidence for its occurrence
creationism and the idea of “fixed species”
- many believed in some form of creationism where species were created by a supernatural being
- as special creations, species were considered to be fixed for all time
fossils and cuvier
- george cuvier made 2 observations from his studies of fossils
- younger fossils, found near surface, more similar to living species than older fossils found deeper
- between layers of rock, some species disappeared, while new ones appeared
catastrophism
belief that boundaries between layers correspond with catastrophes throughout time that wiped out entire species
-evidence of extinction
transmutation and lamarck
- jean lamarck proposed that if an animal acquired a trait during its lifetime, it could pass it to its offspring
- giraffe’s neck
acquired trait
developed over a single lifetime
charles darwin
- first to make a strong convincing argument that species change through time
- ideas were influence by the
- voyage on the beagle
- experience with selective breeding
- thomas malthus (political economist, demographer)
voyage on the beagle
- noticed great variabilities with the shape of beaks among species of finches.
- concluded that small changes accumulating over time were the only plausible explanation for his observations
selective breeding
- enhanced desrired characteristics in future generations
- a few generations of selective breeding could produce populations of pigeons that differed dramatically in appearance (artificial selection)
thomas malthus
- malthu’s essay on the principles of population, which discussed effects of individuals competing for limited food resources
- darwin noted: species typically produce more offspring than needed- some survive and reproduce, others die without reproducing (survival of the fittest)
- these observations led darwin to propose that populations of species change over time
alfred wallace
- proposed a hypothesis almost identical to darwin’s
- both him and darwin presented a paper to linnaean society of london describing biological evolution by natural selection
darwin theory of evolution by natural selection includes 5 observations
- any species, population sizes would increase exponentially if all individuals survived and reproduced successfully
- populations tend to b stable in size, except for seasonal fluctuations
- resources are limited (freshwater)
- members of a population vary in their characteristics; no 2 are exactly the same..
- much of the variation is heritable
darwin’s inferences
- more individuals are produced than the environment can support
- survival depends in part on inherited traits
darwinian evolution
- origins of biological diversity can be explained by purely physical processes
- evolutionary change occurs in groups of organisms (populations) rather than individuals
- evolution is a multistage process occurring across generations
- evolution occurs because some organisms perform better than others in a particular environment
