Bio Ch 23 The evolution of populations

Question 1

How do you explain the evolution of the ground finch after the drought?

Answer 1

Each bird had a particular beak size, which did not growlarger during the drought. Rather, the proportion of large beaks in the population increased from generation to generation: the population evolved not the individual members.

Question 2

What is microevolution?

Answer 2

change in the allele frequencies in a population over generations.

small changes of change over a long period of time

Question 3

What are the three mechanisms that can cause allele frquency change?

Answer 3

natural selection, genetic drift (chance events that alter allele frequencies.)and gene flow (the transfer of alleles between populations)

-only natural selection consistently improves the match between organisms and their environment (adaptations)

Question 4

What is an allele?

Answer 4

A variation in trait

Question 5

What is genetic variation?

Answer 5

differences among individuals in the composition of their genes or other DNA segments.

Question 6

What is the difference between discrete and quantitative characters?

Answer 6

Discrete characters can be classified on an either or basis

ex:you either have a cleft chin or you dont

Most heritable variation involves quanitative variations, which may vary along a continuum within a population.

-variation in skin color, skin colors vary in shade some a little darker some a little lighter. or hair color light brown, blond strawberry blond etc

Question 6

What is frequency?

Answer 6

how often something occurs

Question 7

How can gene variablility be quantified?

Answer 7

Gene variability can be quatified as the average heterozygosity, the average percentage of loci that are heterozygous( this individual has two different alleles for a given locus, where as a homozygous has two identical alleles for that locus)

Question 8

Why does gene variability tend to exceed nucleotide variability?

Answer 8

A gene can consist of of thousands of nucleotides. A difference at only one of these nucleotides can be sufficient to make two alleles of that gene different, increasing gene variability.

Question 9

What is geographic variation?

Answer 9

differences in genetic composition of seperate populations.

• these populations are usually separated by geographic barriers that essentially isolate them from other populations
  ex: The mice arent always willing to walk over a barrier to mate with another mice but maybe a few will and will make a distinct population

Question 10

What have researchers observed in isolated populations?

Answer 10

They observed differences in the karyotypes(chromosome set) of those isolated populations In certain populations chromosomes become fused. because these chromosome-level changes leave genes intact, their phenotypic effects on mice seem to be neutral

Variation between populations appear to have resulted from chance events (drift) rather than natural selection.

Question 11

What is a cline? give an example

Answer 11

a cline is another example of geographic variation, it is a graded change in a character along a geographic axis.Some clines are produced by gradation in an environmental variable

Example: mummichog fish have different enzymes that adapt them to different water temperatures.

Question 12

Why are clines probably a result of natural selection?

Answer 12

because otherwise there would be no reason to expect a close assosiation between the environmental variable and the frequency of the allele.

-selection can only operate if multiple alleles exist for a given locus.

Question 13

When does genetic variation on which evolution depends originate?

Answer 13

When mutation, gene duplication, or other processes produce new genes and new alleles.

Question 14

What is a mutation? how does it differ for different organisms?

Answer 14

muations is a change in the nucleotide sequence of an organisms DNA.

• Iin multicellular organisms, only mutations in cell lines that produce gametes can be passed to offspring.
• the majority of mutations in animals occur in somatic cells and are lost when the individual dies.

Question 15

Do mutations have a negative effect on organisms?

Answer 15

It is unlikely that a new mutation that alters a phenotype will improve it. In fact most such mutations are at least slightly harmful

-a point mutation in a gene that encodes a protein will have no effect on the proteins funtion if the amino acid composition is not changed.

Question 16

Are chromosomal changes that delete, disrupt, or rearrange many loci at once hramful or beneficial?

Answer 16

They are usually harmful however in rare cases chromosomal rearrangements can be beneficial . For exampple the translocation of part of one chromosome to a different chromosome could link DNA segments in a way that results in a positive effect.

Question 17

What is a population?

Answer 17

A population is a group of individual of the same species that live in the same area and interbreed, producing fertile offspring.

ex: californians are a separate population from australians

Question 18

What is a gene pool?

Answer 18

it consist of all copies of every type of allele at every lous in all members of the population.

Question 19

What does it mean to have a fixed allele ?

Answer 19

If only one allele exists for a particular locus in a population, that allele is said to be fixed in a gene pool, and all individuals are homozygous for that allele.

-if there are two or more alleles for a particular locus in a population, individuals may be either homozygous or heterozygous.

Question 20

When studying a locus with two alleles, what do p and q represent

Answer 20

p is used to represent the frequency of one allele and q is used to represent the frequency of the other allele

Question 21

What is a phenotype?

Answer 21

It is the product of inherited genotype and environmental influences

ex: Dr. Trueblood likes twinkies and donuts which makes him festively plump the environment modified his phenotype, had he lived somewhere else where those twinkies and donuts didnt exist he might have a 6 pack

Question 22

What is genetic drift?

Answer 22

Depends on which chromosomes pair with which, how things sequenced together

• chance events
• random assortment
• crossing over

Question 23

Does the environment drive genetic drift?

Answer 23

No its the different assortment, how the chromosomes match up.

Question 24

How and why does genetic variation make evolution possible?

Answer 24

based on the crossing over or how u pair up your chromosomes, somehow can make you better, so lets say we take two of u and make 7 billion people, those that were smarter or more effective would do well those that didnt would get wiped out.

Basically the genetic variation causes multiple alleles, variations in alleles and the best ones through natural selection thrive and would cause evolution in a population.

Question 25

How do you know if a population is evolving?

Answer 25

changes in alleles and allele frequency

Question 26

What is a locus?

Answer 26

The location of a gene

Question 27

What is the Hardy Weinberg principle?

Answer 27

states that frequencies of alleles and genotypes in a population remain constant from generation to generation

Question 28

What are the five conditions for nonevolving populations that are rarely met in nature?

Answer 28

1. ) No mutations
2. )Random mting
3. ) No natural selections
4. ) Extremely large population size
5. ) no gene flow

Question 29

What are the three major factors that alter allele frequencies and bring about most evolutionary change?

Answer 29

• Natural selection
• Genetic drift
• Gene flow

Question 30

for genetic drift, does sample size matter? and does genetic drift increase or reduce genetic variation?

Answer 30

The smaller a sample the greater the chance of deviationfrom a predicted result

Genetic drift tends to reduce genetic variation through the losses of alleles

Question 31

What is the founder effect? give an example

Answer 31

The founder effect occurs when a few individuals become isolated from a larger population

Ex: a flock of birds get blown to a new island where that bird species never existed

Question 32

What is the bottleneck effect? give an example

Answer 32

The bottleneck effect is a sudden reduction in population size due to a change in the environment

Question 33

What is a summary of genetic drift

Answer 33

1. ) genetic drift is significant in small populations
2. )genetic drift causes allele frequencies to change at random
3. ) genetic drift can lead to a loss of genetic variation within populations
4. ) genetic drift can cause harmfufl alleles to become fixed

Question 34

What is gene flow?

Answer 34

Gene flow consists of the movement of alleles among populations

Question 35

Does gene flow tend to increase or reduce variation among populations?

Answer 35

Gene flow tends to reduce variation among populations over time.

Question 36

Can gene flow increase or decrease a populations fitness?