Introduction (1)

Question 1

Together ____ Darwin’s explanation of natural selection, ____ Mendel’s experiments with basic genetic inheritance, and some more recent discoveries are providing answers.

Answer 1

Charles

Gregor

Question 2

What is a species?

Answer 2

A species is a group of organisms that closely resemble each other and are able to breed among themselves, but not with any other species, and produce viable offspring.

Question 3

What is a population?

Answer 3

A population is a group of individuals of the same species occupying a particular habitat.

Question 4

True or false

If all individuals of a population were genetically identical, there would be no natural selection.

Answer 4

True, There must be some genetic variation within a population, which can influence the nature of the offspring, so that environmental conditions can select the best adapted individuals.

Question 5

Darwin’s greatest difficulty was a lack of understanding ______. Gregor Mendel did publish his ideas in Darwin’s lifetime, but Darwin was unaware of them.

Answer 5

inheritance

Question 6

What causes variations in individuals in a species?

Answer 6

The two main ones are sexual reproduction(genetic recombination during meiosis, chance fertilisation and random mating)and mutations.

Question 7

What are the 3 aspects of sexual reproduction?

Answer 7

• Meiosis
• Chance fertilization
• Random mating

Question 8

What is meiosis?

Answer 8

During meiosis there is a rearrangement or shuffling of the genetic material. This includes:
− the random arrangement of homologous chromosomes on the equator.
− crossing-over when bivalents form. This will have been explained in the unit on Meiosis. This results in the formation of a new combination of alleles

Question 9

What is chance fertilisation?

Answer 9

During fertilization the genetic material from the female and male gametes recombines. There is no choosing of which male gamete will fuse with which female gamete. As a result a variety of genotypes (genotypic combinations) are formed in the offspring. The altered genotypes may or may not appear in the phenotype

Question 10

What is random mating?

Answer 10

Random mating means that every female gamete, with her particular genotype, has an equal chance to be fertilized by every male gamete, with his particular genotype in the population.

Question 11

What is a mutation?

Answer 11

A mutation is any sudden alteration in the genetic makeup (genetic code) of an organism.

Question 12

While mutations can occur in ____ and gametic cells in biological evolution we are only interested in this section in gametic mutations

Answer 12

somatic

Question 13

Where do gametic mutations occur?

Answer 13

Gametic mutations occur in gametes and can give rise to offspring that carry the mutation in all of its cells. These mutations, known as germ-linemutations, can be passed on to the offspring and have a strong influence on evolution

Question 14

How do mutations occur? (2)

Answer 14

• Changes in base sequences of DNA. This is the main way new alleles are created and is the main source of genetic variation. ]• Whole chromosomes may be deleted or duplicated, and even the entire chromosomal compliment can multiply in a process called polyploidy. Polyploidy is very important in the evolution of new species of plants.

Question 15

A small ______ of mutations, in the case of evolution beneficial ones, result in a change in the ________. If the change results in organisms adapting better to new or unfavourable conditions, they will survive and breed more successfully than the rest of the population. This is natural selection as nature has selected the better adapted to survive and ____.

Answer 15

percentage
phenotypes
breed

Question 16

How do Galapagos finches show variation in populations due to mutations?

Answer 16

The different beak forms of Galapagos finches .These are pointed and blunt. These differences allowed the finch to occupy the new niches available on the islands and to feed on different types of food. This difference has a genetic basis as it has been found to be a mild mutation. This variation allowed, over time, the development of different species of finch.

Question 17

How do white lions show variation in populations due to mutations?

Answer 17

The colour of the white lions is caused by a recessive trait derived from a harmless mutation. This colouration does not appear to disadvantage their survival; they have been reintroduced into their natural habitat and have been hunting and breeding successfully with other lion for a significant length of time. The white allele might not be expressed when mating occurs with a normal coloured lion but it will reappear when two recessive alleles appear in any offspring.

Question 18

How do bacteria show variation in populations due to mutations?

Answer 18

Resistance of bacteria to antibiotics. Bacteria breed very rapidly. As a result their populations become enormous. Within these vast numbers the chance of mutations occurring is high. The mutations will create considerable genetic variation. When exposed to an antibiotic, most bacteria die, but some variants have a mutation that makes them resistant to the effects of the antibiotic.

Question 19

What is inbreeding?

Answer 19

Inbreeding is mating of genetically closely related individuals

Question 20

In nature inbreeding in a population: (2)

Answer 20

• leads to a loss of genetic diversity, which in nature will prevent evolution.
• results in homozygosity, which can increase the chances of offspring being affected by recessive or harmful traits thus increasing the chances of genetic disorders. In nature this can decrease the biological fitness of a population, i.e. reduces its ability to survive and reproduce. This leads to what is known as inbreeding depression.

Question 21

What is inbreeding population?

Answer 21

− animals have a lower birth weight, do not reproduce so successfully and have less resistance to disease, predation and environmental stress.
− plants produce less seeds, seed germination is poor and their resistance to stress is less.

Question 22

What can inbreeding depression lead to?

Answer 22

Therefore, inbreeding depression can lead to an increase in extinction rates.

Question 23

Why do humans use inbreeding?

Answer 23

Humans use inbreeding to try and establish a new and desirable trait or to continue particular characteristics in an animal or plant group.

Question 24

What does human inbreeding lead to?

Answer 24

However, it often leads to loss of vigour and poor survival as the offspring can become homozygous for a higher proportion of undesirable recessive genes. These undesirable traits can, however be eliminated through further selective breeding or culling.

Question 25

What is outbreeding?

Answer 25

Outbreedingor outcrossing is the production of offspring from the mating or breeding of genetically unrelated individuals.

Question 26

What does outbreeding lead to? (3)

Answer 26

• leads to an increase of genetic variation, which increases the chance of evolution.
• promotes heterozygosity, which decreases the chances of offspring being affected by recessive or harmful traits.
• is a way by which new desirable traits can be introduced into the population that will have a positive effect by increasing the vigour, size and fertility of the offspring. In nature plants that outbreed outperform self-pollinating (inbreeding) individuals

Question 27

Why do humans use outcrossing?

Answer 27

Humans use outcrossing to add desirable and remove undesirable traits in both plants and animals. The vast assortment of new varieties of plants is due largely to outbreeding techniques where new desirable traits are deliberately bred into plants by crossing.