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Chapter 21
evidence for evolution
19
Biology
Undergraduate 2
03/15/2010

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Cards

Term
discribe the evidence for natural selection in darwin's finches
Definition
average beak depth changed yare to year in sync with the annual rainfall
Term
discribe the evidence for natural selection in peppered moths
Definition

-light colored moths in pristine habitats

-dark colored moths in polluted habitats

Term
discribe the data which have led investigators to question the agent of selection in peppered moths
Definition
they didnt factor in the changes in lichens
Term
preserved remains of once-living organisms
Definition
fossil
Term
list the different types of fossils
Definition

-specimens preserved in amber

- siberian permafrost

-dry caves

- fossils preserved as rocks

Term
list what must happen for an organism to form a rock fossil
Definition

- the organism must be buried in sediment

-the calcium in bone or other hard tissues must mineralize

-the surrounding sediment must harden into rock

Term
discribe why fossils are so rare and why only a small percentage of species that once lived are represented in the fossil record
Definition

- usually animal or plant remains decay or are scavenged before the process may begin

-many fossils occur in rocks that are inaccessible to scientists, when they do become available, they are often destroyed by erosion and other natural processes before they can be collected.

Term
discribe two of the most fascinating transitional fossils
Definition

-Archaeppteryx- intermediate between birds and dinosaurs

-tiktaalik- species that bridged the gap between fish and the first amphibions

Term
discribe how the age of fossils is determined by radioactive decay of isotopes like U238
Definition
when a rock is formed, no additional radio active isotopes are added. therefore, by measuring the ratio of radioactive isotope to its derivative, "daughter" isotope, geologists can determine the age of the rock
Term
structures with different appearances and functions that all derived from the same body part in a common ancestor
Definition
homologuous structures (mammals)
Term
explain how homologous structures illustrate natural selection
Definition
natural selection has modified the same intial starting blocks to serve very different purposes
Term
embryos of different types of vertebrates, often are similar early on, but become more different as they develop
Definition
relict embryonic structures (vertebrates)
Term
explain how relict embryonic structures illustrate natural selection
Definition
early in their development, embryos possess pharyngeal pouches, which develop into different structures (humans- various glands and ducts, fish- gill slits)
Term
natural selection can only influence the variation present in a population and becuase of this often results in workable but ___
Definition
imperfect structures (vetebrate eye)
Term
have no apparent function, but resemble structures their ancestors possessed.
Definition
vestigial structures
Term
may occur in distantly related species that are exposed to similar selective pressures
Definition
convergent evolution
Term
discribe convergent evolution using marsupial and placental mammals
Definition

-marsupials are a group in which the young are born in a very immature condition and held in a pouch until mature enough to survive in the external environment

-placentals offspring are not born until they can safely survive in the external environment

Term
is convergent evolution widespread or rare
Definition
widespread
Term
explain why island organisms are often lacking forms found on continents and are closely related to species on nearby continents, even though they may occupy different ecological niches
Definition

-island species usually are closely related to species on nearby continents even if environments are different.

-the species that occur there arrived by dispersing across the water, dispersal from nearby areas is more likely that than more distant sources, though long-distance colonization does occur occasionally

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