humans and the environ 2

Question 1

what is evolution?

Answer 1

Evolution – change in the heritable characteristics of biological populations over successive generations and relies on the process of natural selection.

Question 2

two main scales of evolution

Answer 2

macroevolution

microevolution

Question 3

Darwin’s theory of evolution key points

Answer 3

overproduction
variation 
event - that changes environ
selection 
adaptation 
passing on of genes

Question 4

what is natural selection?

Answer 4

The successful traits will spread through the population.

This change in the frequency of specific traits in the population underlies evolution

Question 5

what are the pro’s of population variation?

Answer 5

Some of these variations (traits) will allow the organisms possessing them to survive and reproduce better than those without these particular traits.

Question 6

What controls the observable traits (phenotype)?

Answer 6

the genotype (genes)

Question 7

what is a gene?

Answer 7

gene is a segment of DNA containing the code which instructs cells to produce a certain protein, which in turn determine a certain trait.

Question 8

how many chromosomes in a human cell?

Answer 8

Every human cell contains 23 pairs of chromosomes, for a total of 46 chromosomes

Question 9

what are some ‘abnormal’ traits caused by?

Answer 9

Some traits are caused by abnormal genes that are inherited or that are the result of a new mutation.

Question 10

what is an allele

Answer 10

one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

Question 11

dominant alleles

Answer 11

will be expressed in the phenotype

Question 12

how do populations generally remain constant in size?

Answer 12

Despite this high potential fertility, natural populations usually remain constant in size, except for small fluctuations.

Not all of the potential offspring survive. - natural selections selects against certain individuals with unfav traits

Question 13

what happens If there are not enough resources for all of the individuals?

Answer 13

there will be competition for those resources.

Survivors represent a small part of the individuals produced each generation.

Question 14

what does it mean to say that variation is heritable

Answer 14

Some of the variation in traits between individuals in the population is heritable
.
Heritable traits can be passed down from one generation to the next.

Question 15

what does it mean when a species adapts to a new environment?

Answer 15

The favoured traits have spread through the population.

Over time, these changes can lead to the formation of a new species.

Question 16

what does environmental pressure cause?

Answer 16

special adaptations

A trait may be favored due to enhanced survival or reproduction when faced with a particular aspect of the environment.

Question 17

what happens when species moves to new environ or current environ changes?:

Answer 17

species adapts to new environment

sometimes results in a new species

Question 18

what is evolution measured as?

Answer 18

measured as changes in relative proportions of heritable traits in a population over several generations.

Question 19

do individual evolves?

Answer 19

no, only populations evolve

Question 20

does natural selection work on heritable or acquired traits?

Answer 20

heritable

Question 21

what are acquired traits?

Answer 21

Acquired traits (developed through life, like knowledge, ideas, skills etc) are not heritable and are not subject to natural selection.

Question 22

what are beneficial traits?

Answer 22

A trait that is beneficial in one place or time may be detrimental in another place or time.

traits that aid the survival of a species

Question 23

is natural selection random?

Answer 23

No. It occurs in response to environmental pressures and results in adaptation.

Question 24

Reproductive success:

What happens during reproductive success?

Answer 24

Their alleles are being passed to the next generation in frequencies that are different from the current generation.

Question 25

ways other than natural selection that allele frequencies can change from one generation to the next.

Answer 25

genetic drift - random loss of alleles
mutation - new mutation can add alleles
nonrandom mating - inbreeding increases that number of homozygous traits
migration - gene flow, shuffles genes between populations, can prevent speciation

Question 26

explain genetic drift

Answer 26

Variation in the relative frequency of different alleles in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce.

Question 27

what is the bottleneck effect? explain

Answer 27

Sometimes a catastrophic event can severely reduce the size of a population.

The random assortment of survivors may have different allele frequencies.

This is a type of genetic drift called the bottleneck effect.

Question 28

what is the founder effect? Explain

Answer 28

when a small group of individuals becomes separated from the main population and form a new population (e.g. Islands). The allele frequencies in their gene pool may be different than the original population.