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Inheritance, variation and evolution Flashcards

1
Q

what are the two type of reproduction?

A

sexual (fusion of gametes) and asexual (one parent)

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2
Q

what type of cell division produces cells from asexual reproduction?

A

Mitosis produces cells for asexual reproduction, so the offspring are all genetically identical as the DNA comes from one parent

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3
Q

What type of cell division produces cells for sexual reproduction?

A

Meiosis produces gametes for sexual reproduction

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4
Q

How are gametes different to normal cells?

A

Gametes produced in meiosis are not genetically identical, also they have half the DNA of a normal cell, so they join the new cell that has the full amount

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5
Q

What are the gametes called in animals?

A

Sperm cells are male gametes and egg cells are female gametes

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6
Q

What are gametes called in flowering plants?

A

Pollen are male gametes and egg cells are female gametes

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7
Q

What happens during meiosis to make gametes?

A

The DNA is replicated,the cells divide twice to give four gamete cells,each gamete is slightly different genetically to the other gametes

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8
Q

Why is it important that gametes are genetically varied?

A

As each gamete is slightly different to the other it means offspring of sexual reproduction are genetically varied too. This gives the species a better survival chance.

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9
Q

Why do gametes have half the DNA of a body cell?

A

So that when the male and female gametes join during fertilisation the new cell formed will have the normal chromosome number

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10
Q

What is DNA?

A

DNA is a chemical polymer made up of two strands joined together and coiled into a double helix shape

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11
Q

What is a chromosome?

A

A chromosome is a molecule of DNA that has been coiled up tightly to make a shorter and fatter molecule

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12
Q

What is a gene?

A

A short section of DNA in a chromosome that codes for a single protein. The code of the DNA in that gene is for a particular sequence of amino acids.

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13
Q

What is a genome?

A

A genome is all of the DNA of an organism. For example, the human genome is all of the DNA that every human would have.

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14
Q

Why is the human genome important?

A

Scientists have studied the human genome and now know what protein every single gene codes for. This will help scientists studying inherited disorders in future.

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15
Q

How can the human genome help with human history?

A

Scientists have used the genome to map where humans migrated from and to in the past

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16
Q

What is an allele?

A

A different version of a gene

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17
Q

What is a genotype?

A

The combination of alleles an organism has

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18
Q

What is a phenotype?

A

The appearance of an individual, the physical characteristic

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19
Q

What does “expressed“ mean in genetics?

A

Expressed means that a characteristic is visible in an individual because the DNA code has been read and the resulting protein made

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20
Q

What is a dominant allele?

A

An allele that is always expressed in the phenotype, represented by a capital letter e.g. B

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21
Q

What is a recessive allele?

A

An allele that only shows in the phenotype when there is no dominant allele in the genotype, it is represented by a lower case letter e.g. b

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22
Q

What is heterozygous mean?

A

The genotype when an organism has two alleles that are different e.g. Bb

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23
Q

What does homozygous mean?

A

The genotype when an organism that has two alleles that are the same as each other e.g. BB(homozygous dominant) bb (homozygous recessive)

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24
Q

Are all characteristics controlled by single genes?

A

Some characteristics are consoled by single genes e.g. blood group but other characteristics are controlled by multiple genes on different chromosomes e.g. height

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25
What is a punnet square diagram?
A boxed shaped diagram that we can use to predict the probability of a particular characteristic being expressed
26
How do we show the probability of a characteristic?
Probability should always be out of 1 ( but often you can turn it into a percentage or fraction )
27
What is an inherited disorder?
Any disorder that can be passed on from one or both parents
28
What is polydactyly?
This disorder gives a sufferer extra fingers and/or toes and is caused by a dominant allele
29
What is cystic fibrosis?
This disorder affects the cell membranes of sufferers and causes thick mucus to be produced which affects many parts of the body and is caused by a recessive allele
30
What is embryo screening?
Testing the DNA of an embryo to find out if it will be a sufferer of a particular disorder. Parents can choose whether to continue with the pregnancy
31
Why do some people think embryo screening is good?
It reduces the number of children born with inherited disorders. This reduces suffering and distress and also reduces the cost for the NHS as fewer treatments are needed.
32
Why do some people think embryo screening is bad?
It results in otherwise healthy embryos being destroyed. Some people disagree with this as every embryo is potential life.
33
How many chromosomes does a normal human cell have?
Every human body cell has 46 chromosomes arranged as 23 pairs. One of each pair came from each parent during fertilisation.
34
What are the sex chromosomes?
Pairs 1-22 code for normal characteristics but pair 23 is the pair that control what sex the person will be. Pair 23 are the sex chromosomes.
35
What are the sex chromosomes in a female?
The two sex chromosomes re the same as each other in females so females have XX.
36
What are the sex chromosomes in a male?
The two sex chromosomes are different to each other in males so they have XY.
37
What are the chances of an embryo being male or female?
Every embryo has a 0.5 probability (50% chance)
38
What is variation?
Any differences in appearance between individuals of the same species in a population
39
What causes variation?
Variation in a population is caused by the different genes they have inherited or the environment they are developed in or both
40
How does variation arise?
Variation in DNA caused by mutations altering the DNA code. Most mutations don’t have any affect on the phenotype but few do.
41
How often do mutations occur?
Mutations are always occurring but most are not noticed as they don’t affect the phenotype of the individual
42
How does natural selection work?
If a mutation causes anew allele, and the new phenotype gives a survival advantage in the environment, the allele will be passed on more often in the offspring
43
What is evolution?
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
44
What does the theory of evolution suggest?
That all living species have evolved from simple life forms that existed over three billion years ago
45
How do new species form?
If two populations of the same species evolve differently they will no longer be able to interbreed and produce fertile offspring so we say they are different species
46
What is selective breeding?
This is when humans take advantage of natural selection to pick genetic characteristics for the offspring to inherit
47
How does selective breeding work?
Pick parents with the desired characteristics and only allow these individuals to breed. From their offspring pick only the ones with the desired characteristics to breed.
48
How long does selective breeding take?
It can take many generations of picking the individuals to breed before the offspring show the desired characteristics
49
What sort of characteristics do we selectively breed for?
Animals that produce more meat/milk,domestic dogs that are gentle, large/unusual flowers,food crops that are resistant to diseases.
50
What is the disadvantages of selective breeding?
Individuals who are selectively bred for a long time become inbred. Inbreeding leads to individuals who are more likely to get disease or inherited defects.
51
What is genetic engineering?
Scientist can modify the genome of an organism by introducing a gene from another organism to give a desired characteristic. The new organism is GM.
52
What does GM mean?
Genetically modified is used to describe any organism that is genetically engineered.
53
What sort of genetic engineering do we do to plants?
To produce bigger and better fruits or be resistant to diseases
54
What sort of generic engineering do we do to bacteria?
To produce useful chemicals such as human insulin to treat diabetes
55
How are genes transferred from one organism to another?
The gene that is useful is ‘cut out’ and transferred into the DNA in cells of other organisms
56
How are the genes cut out?
Enzymes are used to cut the gene from the chromosome and the gene is inserted into a vector (such as a plasmid or virus) which is then used to put the gene into DNA of new cells
57
When would genes be transferred into a different organism?
The transfer has to happen at an early stage of development so that the organism has the gene in all of its cells as it develops
58
What are the advantage of GM crops?
GM crops have been engineered to be resistant to insect attacks or herbicides. Most GM crops have higher yields (more crop is produced per hectare)
59
What are the concerns about GM crops and human health?
Some people feel the effects of eating GM crops haven’t been fully explored
60
What are the concerns about GM crops and the environment?
Some people are concerned that GM crops may start breeding with wild flowers, or may affect insect populations and therefore affect food chains
61
Can GM help people with inherited disorders?
There is ongoing medical research to see if genetic modification can overcome problems caused by inherited disorders such as cystic fibrosis
62
What evidence is there that evolution occurs?
Fossils have been found that support the theory of evolution. Also antibiotic resistance has shown that bacteria have evolved. Plus we know how genes work.
63
Is evolutionary theory by natural selection now accepted?
The theory is widely accepted worldwide as the range of evidence is huge
64
What are fossils?
The remains of organisms that lived millions of years ago and they are found in rocks
65
How do fossils form?
From parts that have not decayed,when parts are replaced by minerals as they decay,as traces such as footprints and burrows
66
What sort of fossils occur?
Apart from the traces fossils are hard parts of animals that have turned to rock,skeletons,shells,claws are mostly fossilised
67
Why can’t we find fossils for early life forms?
Soft body parts don’t fossilise as these part decay. Early life forms were mostly just soft bodied. Bacteria have no hard parts to fossilise so we can’t find evidence of them.
68
Why can’t scientists prove how life on earth began?
As scientists are sure that early life started with fossils,but there is no physical evidence to support this theory so it can’t be proved
69
What can scientists find out from fossil evidence?
Scientists can see how much or how little life on Earth has changed over time. Some deep ocean species have changed the least e.g. shark
70
What is an evolutionary tree?
A diagram that shows how different species are linked over evolutionary time. Relationships and common ancestors can be seen in evolutionary trees.
71
What does extinction mean?
When every individual of a species on earth is dead, we say that species has become extinct
72
Why do species become extinct?
If a species cannot survive environmental changes, then every member of that species will die
73
Do humans cause all extinctions?
No many species were extinct before humans existed, but in modern times we have become responsible for many species becoming extinct
74
What do humans do that causes species to become extinct?
Humans destroy habitats,reduce food availability or hunt and kill other species. All of these can cause a species to become endangered or extinct
75
Why do bacteria evolve more quickly than other species?
Bacteria reproduce very quickly so they can get through many generations in a few weeks
76
What do we mean by resistant bacteria?
Bacterial pathogen strains that are not easily killed by antibiotics and so difficult to treat
77
How do bacteria become resistant?
Mutations occur to the DNA in bacteria. This produces new strains and some of these are resistant to particular antibiotics. They survive,reproduce and increase in number.
78
What is the worse problem with resistant bacteria?
Some bacterial strains can evolve to become resistant to several antibiotics. There may be no effective treatment for these strains at all.
79
What is MRSA?
A bacterial strain that is resistant to many antibiotics and causes several deaths each year.
80
How do doctors help to reduce the risk of bacterial resistance?
Doctors should not prescribe antibiotics for non-serious bacterial infections or for viral infections.
81
How can patients help to reduce the risk of bacterial resistance?
Patients given antibiotics should complete the whole course of antibiotics so that all the bacteria is killed and none survive to mutate and form resistant stains.
82
How can the agriculture industry help to reduce the risk of resistance?
Antibiotics used to be given to farm animals regularly in their feed and this use should be restricted to only vets treating an emergency
83
Why can’t we just develop new antibiotics for the resistant strains?
Developing new antibiotics is expensive and slow. Drug development can’t keep pace with the speed at which new resistant strains are emerging
84
What is classification?
Placing species of living things into non-overlapping groups depending on their structure and characteristics. THIS SYSTEM WAS DEVELOPED BY CARL LINNAEUS.
85
What groupings did Linnaeus develop?
Kingdom phylum class order family genus and species (king prawn curry or fat greasy sausage)
86
How are organisms named in Linnaeus’ system?
Binomial system naming where each organism is given two names, its genus and species name
87
Has classification changed since Linnaeus developed it?
Yes, better biological evidence has seen species move into more appropriate groups. Also new models of classification have been proposed.
88
What sort of evidence is needed to make changes to classification?
Better microscope evidence of internal cel structures and better understanding of biochemical processes within cells and organisms
89
Who is Carl Woese?
A scientist who proposed the new “three domain system“ based on evidence from chemical analysis
90
What are the three domains?
Archaea,true bacteria,eukaryote (protists, fungi,plants,animals)
91
What are archaea?
Primitive bacteria usually living in extreme environments (they are not evolve like true bacteria, due to the extreme conditions they need to be adapted to survive)
92
How can evolutionary trees be used in classification?
Relationships between living organisms and extinct organisms can be seen from a tree. Fossil evidence is used to help build the tree and link with the past.

Biology (10 decks)

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