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biology 16-17

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Most inheritable differences
are due to gene shuffling that occurs during the production of gametes
list three ways that natural selection can affect the distribution of phenotypes
directional, stabalizing, and disruptive
What is the status of Darwin's theory today?
It changes overtime as new data is gathered
Directional
individuals at one end of the curve have higher fitness than indivuduals in the middle or at the other end
Darwin explained the distribution of finch species on the Galapagos islands
They had descended with modification from a common mainland ancestor
Homologous structures
provide strong evidence that all four-limbed animals with backbones have descended, with modifications, from common ancestors
How did Darwin explain the exsistence of similar but unrelated species?
similar environment they wound up with similar traits
the number of phenotypes produced for a given trait
depends on how many genes control the trait
Why do mutations occur
mistakes in the replication of DNA or as a result of raditation or chemicals in the environent
sexual reproduction
it is a major source of variation in many populations, it can produce many different phenotypes, it can produce many different genetics combinations
A gene pool compared with the number of times other alleles occur is called the
relative frequency of the allele
Accroding to Darwin's theory, what happens to individuals whose characteristics are not well suited to their environment
they die
sources of genetic variation include
mutation and gene shuffling
if a trait had no effect on an organism's fitness, what would happen to the allele for that trait
not under pressure from natural selection
random change in allele frequencies in small populations is called
genetic drift
most traits are
controlled by a more than one gene
the combined genetic information of all members of a particular population is a
gene pool
Darwin believed that all organisms on Earth are united into a single tree of life by
common descent
Mutation
any change in a sequence of DNA
true about mutations
they can be limited to a single base DNA
Darwins theory of evolution
There is variation in nature, there is struggle for excistence, species change over time
stabilizing
individuals near the center of the curve higher fitness than individuals at either end
an increase in the average size of beaks in Galapagos finches is an example of
directional selection
Mendel's work on inheritnece was published
during Darwin's lifetime
Which two important factors was Darwin unable to explain without an understanding of heredity?
how harritable traits pass from one generation to the next. How variation apeared
natural selection on single-gene traits
can lead to changes in allele frequencies
organs that are so reduced in size that they are just vestiges, or traces, of homologous organs in other species are called
vestigal organs
disruptive
individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle
Structures that have different mature forms but develop form the same embryonic tissues are called
homologeus structures
list the three fields that collaborate today to explain evolution
genetics, DNA, Melcualar techniqued
if a trait made an organism less liekly to survive and reproduce, what would happen to the allele for that trait
it can disappear forever
a collection of individuals of the same species in a given area is a
population

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