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biology gcse > inheritance, variation and evolution (paper 2) > Flashcards

inheritance, variation and evolution (paper 2) Flashcards

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1
Q

what does meiosis lead to

A

non identical cells forming

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2
Q

what does mitosis lead to

A

identical cells forming

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3
Q

what are sex cells in animals

A

sperm and egg cells

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4
Q

what are sex cells in plants

A

pollen and egg cells in flowering plants

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5
Q

describe the process of meiosis

A

copies of the genetic information are made

the cell divides twice to form four gametes, each with a single set of chromosomes

all gametes are genetically different from each other

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6
Q

advantages of sexual reproduction

A

produces variation in the offspring

if the environment changes variation gives a survival advantage by natural selection

natural selection can be speeded up by humans in selective breeding to increase food production

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7
Q

advantages of asexual reproduction

A

only one parent needed

more time and energy efficient as do not need to find a mate

faster than sexual reproduction

many identical offspring can be produced when conditions are favorable

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8
Q

give an example of when an organism reproduce sexually and asexually

A

Malarial parasites reproduce asexually in the human host, but sexually in the mosquito.

Many plants produce seeds sexually, but also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils.

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9
Q

what structure does DNA have

A

a double helix structure

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10
Q

what is the genome

A

the entire set of genetic material in an organism

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11
Q

what is DNA

A

DNA is a polymer made up of two strands forming a double helix. The DNA is contained in structures called chromosomes

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12
Q

what is a gene

A

a small section of DNA on a chromosome.

Each gene codes for a particular sequence of amino acids, to make a specific protein

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13
Q

what is the importance of understanding the human genome

A

search for genes linked to different types of disease

understanding and treatment of inherited disorders

use in tracing human migration patterns from the past

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14
Q

describe the structure of a nucleotide

A

the oval shape is a phosphate

the pentagon shape is a sugar

the square shape is a base

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15
Q

what are the four bases that DNA contains

A

A, T, G, C

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16
Q

what do a sequence of 3 bases code for

A

a particular amino acid

The order of bases controls the order in which amino acids are assembled to produce a particular protein

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17
Q

what happens during protein synthesis

A
  1. to make proteins, ribosomes use the code in the DNA , DNA cannot move out of the nucleus because the DNA is too big. So the cell needs to get the code from the DNA to the ribosome
  2. this is done using a molecule called mRNA which is made by copying the code from DNA , it carries the code between the DNA and the ribosomes
  3. the correct amino acids are brought to the ribosomes in the correct order by carrier molecules
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18
Q

what is a mutation

A

a random change in an organisms DNA

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19
Q

what do mutations do

A

change the sequence of the DNA bases in a gene which produces a genetic variant

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20
Q

what happens if a mutation causes a change in shape

A

could affect its ability to preform its function e.g. the active site of an enzyme changing shape - will become denatured

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21
Q

what is a gamete

A

sex cells - egg and sperm cells

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22
Q

what is a chromosome

A

thin strands of DNA (deoxyribonucleic acid).

They are subdivided into genes.

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23
Q

what is a gene

A

a section of DNA on a chromosome that codes for a specific protein or characteristic

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24
Q

what is an allele

A

an alternative form of a gene

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25
Q

what does homozygous mean

A

the alleles are identical for the same characteristic

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26
Q

what does heterozygous mean

A

the two alleles are different

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27
Q

what is a genotype

A

chemical makeup of DNA that causes a particular phenotype.

28
Q

what is a phenotype

A

the physical expression of DNA.

29
Q

what type of alleles causes polydactyl

A

caused by a dominant allele.

30
Q

what type of alleles cause cystic fibrosis

A

is caused by a recessive allele

31
Q

arguments for embryo screening

A

will help people to stop suffering

treating disorders costs the government a lot of money

there are laws to stop it going to far, at the moment parents cannot even select the sex of their baby

32
Q

arguments against embryo screening

A

implies that people with genetic problems are undesirable - this could increase prejudice

there may be a point where everyone wants to screen heir embryos so they can pick the most desirable one

screening is expensive

33
Q

what are the chromosomes in females and in males

A

females - (XX)

males - (XY)

34
Q

how many pairs of chromosomes do ordinary body cells contain

A

23

35
Q

what differences may cause variation in a population

A

the genes they have inherited (genetic causes)

the conditions in which they have developed (environmental causes)

a combination of genes and the environment

36
Q

what is the theory of evolution

A

a change in the inherited characteristics of a population over time through a process of
natural selection which may result in the formation of a new species.

37
Q

impact of selective breeding on food plants and domesticated animals

A

animals that produce more meat or milk

crops with disease resistance

dogs with a good, gentle temperament

decorative plants with big or unusual flowers

38
Q

how does selective breeding work

A

involves choosing parents with the desired
characteristic from a mixed population. They are bred together. From the offspring those with the desired characteristic are bred together. This
continues over many generations until all the offspring show the desired characteristic

39
Q

what is selective breeding

A

the process by which humans breed plants and animals for particular genetic characteristics.

40
Q

what can be negatives of selective breeding

A

can lead to ‘inbreeding’ where some breeds are
particularly prone to disease or inherited defects.

41
Q

what is genetic engineering

A

a process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

42
Q

how have plant crops been genetically engineered

A

to be resistant to diseases or to produce bigger better fruits

43
Q

how have bacterial cells been genetically engineered

A

to produce useful substances such as human insulin to treat diabetes

44
Q

pros of genetically engineering crops

A

can increase the yield, making more food

crops could be engineered to contain nutrients that are missing - these can be useful in developing nations

they are already being grown in some places and are not causing any problems

45
Q

cons of genetically engineered crops

A

some people say it will reduce the number of wild flowers - reducing farmland biodiversity

not everyone thinks they are safe and their has not been enough research into the affects the can have on human health

46
Q

what are the main steps in the process of genetic engineering

A

enzymes are used to isolate the required gene; this gene is inserted into a vector, usually a bacterial plasmid or a virus

the vector is used to insert the gene into the required cells

genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics

47
Q

what is a tissue culture

A

using small groups of cells from part of a plant to grow identical new plants. This is important for preserving rare plant species or commercially in nurseries.

48
Q

give examples of methods of cloning

A

cuttings

embryo transplants

49
Q

what is the method for adult cell cloning

A

The nucleus is removed from an unfertilised egg cell.

The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell.

An electric shock stimulates the egg cell to divide to form an embryo.

These embryo cells contain the same genetic information as the adult skin cell.

When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development

50
Q

what is the theory of evolution by natural selection

A

Individual organisms within a particular species show a wide range of variation for a characteristic.

Individuals with characteristics most suited to the environment are more likely to survive to breed successfully.

The characteristics that have enabled these individuals to survive are then passed on to the next generation

51
Q

why was the theory of evolution by natural selection only gradually accepted

A

the theory challenged the idea that God made all the animals and plants that live on Earth

there was insufficient evidence at the time the theory was published to convince many scientists

the mechanism of inheritance and variation was not known until 50 years after the theory was published

52
Q

what was Lamarcks theory

A

the idea that changes that occur in an organism during its lifetime can be inherited.

We now know that in the vast majority of cases
this type of inheritance cannot occur.

53
Q

what are the steps that create a new species

A
  1. there are two population of the same species
  2. physical barriers separate the populations
  3. populations adapt to new environments
  4. there is now the development of a new species

(this process takes place over millions of years)

54
Q

what were the three important conclusions Mendel made through his pea plants

A

1 - characteristics in plants are determined by hereditary units

2 - hereditary units are passed on to offspring unchanged from both parents

3 - hereditary units can be dominant or recessive

55
Q

why was the importance of Mendel’s discovery not recognised until after his death

A

scientists had no idea about genes, DNA or chromosomes

scientists realised how there were striking similarities in the way that chromosomes and Mendel’s “units” acted

56
Q

how do fossils support the theory of evolution

A

they contain the remains of organisms from thousands of years ago, they can tell us a lot about how much or how little an organism has changed

57
Q

what are the three ways that fossils form in rocks

A

from gradual replacement by minerals

from casts and impressions

from preservation in places where no decay happens

58
Q

how is antibiotic resistance an example of evolution by natural selection

A

Antibiotics usually kill bacteria, but in this case the mutation means the bacteria cannot be destroyed by the antibiotic.

This evolution of antibiotic resistance in bacteria is an example of natural selection leading to evolution

59
Q

why is the fossil record incomplete

A

Many early forms of life were soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity.

This is why scientists cannot be certain about how life began on Earth

60
Q

what are factors that may contribute to the extinction of a species

A

new diseases

new predators

new, more successful competitors

changes to the environment over geological time, such as climate change

a single catastrophic event, such as a massive volcanic eruption or a collision between an asteroid and the Earth

61
Q

how do you reduce the rate of development of antibiotic resistant strains

A

doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections

patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains

the agricultural use of antibiotics should be restricted.

62
Q

who created the classification of living organisms

A

Carl Linnaeus

63
Q

what is the order of classification

A

kingdom, phylum, class, order,
family, genus and species.

64
Q

who developed the three domain system

A

Carl Woese

65
Q

what is the order of the three domain system

A

archaea (primitive bacteria usually living in extreme environments)

bacteria (true bacteria)

eukaryota (which includes protists, fungi, plants and animals).

biology gcse (7 decks)

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