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Biology Paper 2 > B6 Variation > Flashcards

B6 Variation Flashcards

1
Q

What is variation

A

The difference in characteristics of individuals in a population

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2
Q

What are the 3 main causes of variation

A

. Genetic causes (genes they have inherited)
. Environmental causes (the conditions in which they have developed
. A combination of genes and environment

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3
Q

What are mutations

A

Changes to the genetic code. They take place all the time. Most have no effect on the phenotype. Some can have an effect on the phenotype. A small number of mutations actually determine the phenotype

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4
Q

What were the first life forms on earth

A

Single cells

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5
Q

What does evolution by natural selection mean

A

All species of living things evolved from these simple life forms - single cells

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6
Q

What is evolution

A

The change in the inherited characteristics of a population over time through the process of natural selection

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7
Q

What happens when 2 populations of species become so different in phenotype

A

They can no longer interbreed to produce fertile offspring. the 2 populations have become different species

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8
Q

What is selective breeding

A

Process by which humans breed plants and animals for particular genetic characteristics

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9
Q

Give 4 examples of selective breeding with reasoning

A

. Dogs - gentil nature
. Food crops - disease resistant
. Cows - produce more milk/more of them
. Plants - larger flowers

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10
Q

How is selective breeding carried out

A

. Select the largest male and female from a mixed population of cows
. Breed them together - sexual reproduction. This gives variation in offspring so the offspring will be a mixture of larger and smaller animals
. Select the largest male and female from the offspring and breed them together
. Continue to do this over many generations until offspring are large

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11
Q

What are the problems with selective breeding

A

. If we breed closely related animals or plants, then we can get interbreeding. This can cause some breeds to be:
Prone to disease
Prone to inherited defects

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12
Q

How are gentecially modified crops (GM crops) produced

A

By transferring genes Into plants

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13
Q

Why are plants genetically modified

A

. Produce greater yield than normal crops
. Resistant to disease and insect attack
. Bigger and better friut
. Some are resistant to herbicides

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14
Q

Why are ppl against GM crops

A

. Could affect populations of wild flowers and insects
. Some ppl feel we need more research on the health effects of eating GM crops

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15
Q

What are gene therapy

A

. Genetic modification is currently being explored as a way to treat inherited disorders in humans
. Long term effects are not known
. If we modify a gene, we do not know the potential effects on other genes

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16
Q

How is genetic engeneering carried out

A

. Identify the gene we want to transfer (can be gene from human, plant, animal)
. Use enzyme to isolate the gene
. Insert DNA into a vector. This can be a placmid or a virus
. The disired gene is transfered into the cells of the target organisation

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17
Q

Give example of genetic engeneering

A

. In genetic engineering, genes from one organisation are cut out and transfered to cells of a different organism. The genome of the bacteria is modified and now includes a human gene
Eg: insulin
. Insulin is hormone which helps regulation blood glucose concentration in humans
. Ppl with type 1 diabetes can’t make own insulin so they inject themselves with insulin regularly. Bacteria modified to contain human insulin gene
. This bacteria now produces human insulin
. The insulin can be purified and used for type 1 diabetes

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18
Q

What are fossils

A

Remains fog organisms form millions of years ago which are found in rocks

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19
Q

Describe 3ways in which fossils are formed

A

. Can be formed where parts of the organisms have not ddcayed (happens when conditons for decay are absent eg: to cold, no oxygen, no water)
. Parts of organism are replaced with minerals as they decay
. Fossils can be preserved and traced for organisms eg footprints, burrows

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20
Q

What are the probs with fossils

A

Earliest life forms where soft bodied (didn’t have shell or Skelton). They very early form fossils
. Fossils that did form have been destroyed due to change in rock in the earth’s crust. Because there are very little fossils of the earliest life form scientists can’t be sure how life started exactly

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21
Q

What is ment by extinction

A

When no remaining individuals of that species Is still alive

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22
Q

How and why do species become extinct

A

. Catestrophic event eg astroid hit earth
. Environmental changes eg weather patterns
. A new disease/predator (could kill all of the individuals of a species and make them extinct
. A new, more successful species evolves and competes with it

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23
Q

What are some key points about bacteria

A

. Can evolve rapidly because they reproduce at a fast rate
. Antibiotics kill bacteria
. Used in medicine, farming - prevent animals from developing bacterial disease

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24
Q

How does bacteria become antibiotic resistant

A

. Mutation could make bacterium resistant to antibiotics
. If we use antibiotic, all bacteria is killed apart from the bacterium which is resistant to antibiotics
. This antibiotic resistant strain survives and reproduces without any completion from other bacteria. Overtime the population of this rises the spreads as people are not immune to it and there is no effective treatment

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25
Q

How do u reduce the development of antibiotic resistant bacteria

A

. Doctors should no prescribe antibiotics inappropriately such as treating non serious or viral infections
. Patients should complete there course of antibiotics so all bacteria dies and non survive to mutate and form resistant strains
. The agricultural use of antibiotics should be restricted

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26
Q

What are the issues with developing new antibiotics

A

. Takes a long time
. Expensive
. Hard to keep up with the emergence of new resistant strains

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27
Q

What classification system did Carl linius come up with

A

System developed to classify species into different categories based on structure and characteristics. Has plant kingdom and animal kingdom

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28
Q

Who came up with the 3 domane system

A

Carl woese

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29
Q

What is the 3 domain system

A

. Archea:
Primitive bacteria found in extreme conditons such as hot springs
. Bacteria:
True bacteria
Lives in the human digestive system
. Eukaryota:
Include animals, plants, fungi, protist

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30
Q

What is an evolutionary tree

A

Method used by scientists to show how closely related organisms are to each other

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31
Q

What data is used for an evolutionary tree

A

Classification data eg: DNA
And fossil data for extinct organisms

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32
Q

What is the problem with the data used for an evolutionary tree

A

Fossils records not complete for many species

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33
Q

Describe sexual reproduction

A

. Produces genetically different cells using 2 organisms
. Firtilistation occurs
. Involves gametes
. When environmental changes occur, variation gives a survival advantage by natural selection
. Gives species a greater chance at survival when conditons become challenging

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34
Q

Describe asexual reproduction

A

. Produce genetically identical cells
. Only 1 parent
. Doesn’t involve gammetes
. More time and energy efficient - no need to find a mate
. Faster than sexual reproduction
. Many identical offspring can be produced when conditions are favourable
. Risk they can all die if conditons are unfavourable

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35
Q

Describe the process of miosis

A

. Has 46 chromosomes before cell starts to divide.
. DNA duplicates. Chromosomes line up at centre of cell
. Now there are 92 chromosomes as DNA had duplicated. Paires of chromosomes are pulled apart to create 2 cells.
. Now there Are 46 chromosomes in each cell. Cell divides again
. Now there are 23 chromosomes in each cell

36
Q

Describe the structure of DNA

A

DNA is a polymer
. It is made up of 2 strands coiled together in a shape of a double helix

37
Q

What is a gene

A

A small section of DNA

38
Q

What is a genome

A

An entire section of genetic material in an organism

39
Q

Describe the benefits of scientists studying the human genome

A

. Help understand inherited diseases better and help us figure out how to treat them
. Help trace backgrounds and migration patterns
. Allow scientists to identify genes in the genome that links to different diseases

40
Q

What is a gamete

A

Sex cell that contains 23 chromosomes

41
Q

What is a chromosome

A

Really long molecule of DNA

42
Q

What is a gene

A

A small section of DNA found in chroma some that codes for a specific protien

43
Q

What is an allele

A

Different types of genes

44
Q

What is a dominant allele

A

Alleles that over rule other alleles

45
Q

What is a recessive allele

A

Neither allele over rules the other allele

46
Q

What is homozygous

A

When 2 alleles for a particular gene are the same

47
Q

What is hetrozygous

A

When 2 alleles for a particular gene are different

48
Q

What is a genotype

A

The combination of alleles

49
Q

What is a phenotype

A

The characteristics of an allele

50
Q

What is cystic fibrosis

A

. A disorder of cell membranes
. Contolled by a single gene

51
Q

What kind of conditon is cystic fibrosis

A

Recessive - need 2 recessive alleles to get cystic fibrosis

52
Q

What is the genotype of someone with cystic fibrosis

A

Homozygous
cc

53
Q

What is the genotype of a carrier of cystic fibrosis

A

Hetrozygous
Cc

54
Q

What is polydactly

A

When a person has extra fingers or toes. It is an inherited disorder

55
Q

What kind of conditon is polydactly

A

Dominant allele

56
Q

What is the genotype of someone with polydactly

A

Man - hetrozygous
Woman - homozygous

57
Q

What happens in embryo screening

A

. Embryos are screened and tested to see if they have alleles for inherited disorders
. Embryos wich do not have the defective allele are implanted into the woman
. These can develop healthy offspring

58
Q

What are some issues with embryo screening

A

. Expensive - people believe money should be spent elsewear in the service
. Embryos are destroyed
. Unethical

59
Q

What is gene therapy

A

When scientists are able to correct faulty alleles and do this to treat inherited conditions

60
Q

What Are the chromosomes for a male

A

XY

61
Q

What are the chtomosomes for a female

A

XX

62
Q

What is the nam given to the genetically identical offspring that asexual reproduction produces

A

Clone

63
Q

Describe the method of cloning plants using cuttings

A

. Make cutting of plant u want to clone
. Dip the end in rooting powder - rooting powder contains plant hormones and this encouraged the plants to develop roots
. This produces genetically identical clone of the starter plant
. Good for if u want a few clones of a plant

64
Q

Describe the method of cloning plants using tissue culture

A

. Take plant we want to clone and divide it into hundreds of tiny peaces (each peace contains a small number of cells)
. Incubate the small group of cells with plant hormones. The hormones stimulate plant to grow and develop into full grown clones
. The conditons of tissue culture must be sterile so we don’t introduce any microorganisms such as bacteria

65
Q

Why is tissue culture usefull

A

. It is most usefull in commercial plant nurseries
. allows growers to produce thousands of gentically identical plants quickly and cheaply
. Because they are clones, gardeners can be certain that they will get the characteristics they want
. Also used to preserve rare species of plants

66
Q

How does animal cloning work?

A

. Collect sperm and egg cell from animal with the characteristics we want
. Firtilistation occurs producing a fertilised egg
. Allow fertilised egg to develop into early stage embryo
. Use a glass rod to split the embryo into 2
. Transplant the 2 embryos into host mothers
. The embryos will grow and develop and when born will produce 2 identical offspring

67
Q

What are the problems with embryo transplant

A

Cantbe certain offspring will have characteristics we want. A solution to this is adult cell cloning

68
Q

How does adult cell cloning work

A

. remov cell from the animal we want to clone.
. Remove nucleus from that cell
. Take an unfertilised egg from the same species
. Remove nucleus from unfertilised egg cell
. Now it doesn’t contain genetic information
. Insert nucleus from original adult body cell into the empty egg cell
. Give the egg cell an electric shock to make it divide to form an embryo
. Insert into womb if female womb which gives birth go clone

69
Q

What are the benifits of adult cell cloning

A

We are cloning an adult so we know what kind of characteristic we will have

70
Q

Introduction to Charlse darwin

A

. Went on expedition around the world
. Collected lots of animal and plants
. Spent many years studying geology and fossils
. The fossils showed that many species of animals and plant that are alive today are similar to extinct species

71
Q

What was Darwin theory

A

Within a species, we can see a wide range of genetic variation for any characteristic
Natural selection - individuals with characteristics most suited to Th environment are more likely to survive and breed successfully.

72
Q

What was the book Darwin published and when was it published

A

On the origin of species published in 1859

73
Q

Why was Darwin theory extremely controversial and only partially accepted

A

. Challenged idea of God and that he created all species
. Not enough evidence to back up theory
. Ppl didn’t understand how characteristics were inherited
. Genetics were not understood until after 50 years
. Scientists had the theories

74
Q

What was Jean baptise lamarks theory

A

That when a characteristic is regularly used, it becomes more developed

75
Q

What wa the issues with lamarks theory?

A

We now k ow in vast majority of cases, changes that occur in an organisms life time can’t be passed into offspring

76
Q

What wa Alfred russle Wallace interested in

A

Colouration of animals. He wanted to know how warning colours had evolved

77
Q

What did wallice notice

A

How closely related species were often divided by geographical barriers like rivers

78
Q

How are species formed

A

Eg: snails
. Island contains snails which can interbreed
. A river changed course and seperated the population of snails into 2 populations
. Overtime, natural selection will favour different alleles on the 2 sides of the island
. Due to no interbreeding between 2 populations, any mutations that occur can’t spread
. Over many generations, 2 populations of snails will begin to change
. River may change course again and snails will beign to mix
. 2 populations so different they can’t produce fertile offspring
. Snails are now 2 different species

79
Q

What is the polymer of DNA made up of

A

Different nucleotides

80
Q

Describe the structure of a nucleotide

A

. Phosphate - doesn’t change
. Sugar molecule - doesn’t change
. Base - does change

81
Q

What are the 4 different bases. give information about them

A

A, C, G and T. DNA strands are complimentary so the same base strands always pair up. C always pairs with G. A always pairs with T

82
Q

What are protien made up of

A

Polymers of amino acids

83
Q

What does the sequence of the amino acid determine

A

The shape and function of the protien it makes up

84
Q

What does the shape of the protien determine and what is the job of protien

A

shape determines It’s function
Job - enzymes, hormones or forming structures in the bogy like collagen

85
Q

Describe how protien synthesis occurs

A

Stage 1:
. Takes place in the nucleus. This process is called transcription
. Base sequence of gene is copied into complimentary strand of molecule.
. This is called mRNA (messenger RNA). This passes out the nuclues and into to cytoplasm
Stage 2:
. Takes place in cytoplasm. Called translation
. The mRNA attaches to a ribosome. Amino acids are Brough to the ribosomes on carrier molecules. These are called tRNA (transfer RNA)
. The ribosomes read the triplets of bases
. Once the protien chain Is complete, it folds into unique shape that let’s it do its job

86
Q

What are the 2 types of mutations?

A
  1. The base has changed but it has not changed the amino acid sequence
    . This is because sometimes different base triplets code for the same amino acid so there is no affect on shape or function of protien
  2. Protien has a different amino acid.
    . This changes shape of protien
    . Critical because now active sight of enzyme has changed shape so now subrate cant fit
    . Or it effects structure protien like collagen - looses it’s strength
87
Q

What occurs in non coding parts of DNA? How can mutation affect this

A

Genes can be turned on and off
Mutation can affect how these genes can turn on and off

Biology Paper 2 (3 decks)

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