AQA Biology Paper 2 > Inheritance,variation And Evolution > Flashcards

Inheritance,variation And Evolution Flashcards

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1
Q

What are the gametes in humans?

A

*egg cells
*sperm cells

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2
Q

How many chromosomes are in a human gamete?

A

*23 single chromosomes

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3
Q

How many chromosomes do human cells contain ?

A

*23pairs of chromosomes

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4
Q

What are the gametes in plants?

A

*pollen and egg cells

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5
Q

What are the features of sexual reproduction?

A

*male and female gametes fuse(fertilisation happens)
*offspring variation (bc there is info of both parents being passed to offspring)
*meiosis happens

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6
Q

What are the features of asexual reproduction ?

A

*offspring is genetically identical to parent(bc there is only info of one parent being passed down)
*meiosis does not take place and only involves mitosis

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7
Q

Where does meiosis take place?

A

*testes in males
*ovaries in females

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8
Q

Describe the process of meiosis?

A

*first stage- all of the chromosomes are copied
*second stage- cell divides into two
Third stage- both cells divide into two to form 4 gametes in total

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9
Q

What are the stages after meiosis?

A

*fertilisation( female and male gametes fuse to restore normal cell)
*cell divides by mitosis to form embryo
*embrionic cells differentiate to form different specialised cells to make up an organism

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10
Q

What are the advantages of sexual reproduction?

A

*genetic variation-if environment changes then variation means the offspring has a chance of survival through natural selection
*gives species a greater chance of survival if conditions become challenging

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11
Q

Advantages of asexual reproduction?

A

*no need to find a mate
*time and energy efficient
*fast

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12
Q

Disadvantages of asexual?

A

*if conditions become unfavourable they could die

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13
Q

Where does malaria reproduce sexually and where does it reproduce asexually?

A

*reproduces asexually in the human host
*reproduces sexually in the mosquito

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14
Q

What is reproduction like in fungus?

A

*can release asexually produced spores which form into have identical fungi formed
*can release sexually produced spores which create variation in the case of unfavourable changes to environment

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15
Q

What is reproduction like in plants?

A

*strawberries reproduce asexually by sending out runners
*daffodils reproduce asexually where it has underground bulbs that produce buds

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16
Q

What is the structure of DNA?

A

*DNA strands are made up of repeating units of nucleotides
*each nucleotide consists of a phosphate group, a sugar and one of the bases
*phosphate and sugar makes up the backbone of the DNA
*a base is attached to each sugar
*strands wrap around to form a double helix

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17
Q

What are the pairings of the bases?

A

*a and t
*c and g
*complementary base pairing

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18
Q

What is a gene?

A

*small section of DNA on a chromosome
*a sequence of bases that codes for particular sequence of amino acids which come together to form a specific protein
*tells us in what order to put the amino acids together

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19
Q

What do triplet come together to form?

A

*amino acids

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20
Q

What is the human genome?

A

*the entire genetic material that makes a human

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21
Q

How does understanding the human genome help us?

A

*helps us to identify genes in genome that are linked to dif diseases
*helps to understand and treat inherited disorders like cystic fibrosis
Helps to trace human migration patterns to find people discover their ancestry

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22
Q

Describe process of transcription?

A

*transcription-the base sequence of the gene is copied into a complementary template molecule(mRNA)
* mRNA passes out of nucleus into the cytoplasm

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23
Q

Describe process of translation?

A

*mRNA molecule attaches to ribosome
*amino acids are brought to the ribosome on carrier molecules(tRNA)
*ribosome reads triplets of bases and joins together correct amino acids in correct order

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24
Q

What is a mutation ?

A

*a change in the DNA base sequence

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25
What are substitutions?
*it is a type of mutation *when a random base in DNA changes to a different base
26
What are insertions?
*a type of mutation *when extra base is inserted into the sequence pushing them along to the next
27
What are deletions?
*a type of mutation *when one of the bases are deleted and there are less bases now
28
What are alleles ?
*versions of the same gene
29
What is a genotype?
*show the allele present *e.g Ee
30
What is homozygous?
*when someone has two copies of the same allele
31
What is the phenotype?
*characteristic caused by someone alleles
32
What is heterozygous?
*when someone has two different alleles
33
What is cystic fibrosis a disease of?
Cell membranes
34
What type of gene would the one cor cystic fibrosis be?
*recessive for both
35
What would the alleles of a cystic fibrosis carrier be ?
*dominant and recessive
36
What is polydactyly?
*when people have extra fingers or toes
37
What type of allele causes polydactyly?
*dominant allele
38
What is embryo screening?
*when embryos are tested to see if they have the alleles for inherited disorders
39
What are the issues with embryonic screening?
*expensive *implies people with genetic problems are undesirable (could increase prejudice) *may be point where people can screen their embryos so the6 can pick particular traits
40
41
What are pros of embryonic screening?
*will help stop people from suffering *there are laws to stop it going to far(rn ppl aren’t allowed to choose sex of their baby)
42
Think abt if yk how to do the family trees
*if u don’t go and look at a video on it u dummy
43
What are the sex chromosomes of a male?
*XY
44
What are the sex chromosomes of a female?
*XX
45
What are the three types/causes of variation?
*genetic variation *environmental variation *genes and the environment
46
What are examples of genetic variation?
*hair colour and eye colour *they are inherited by genes of parents
47
What are some e.g of environmental variation?
*language you speak and plant growth *because we get these characteristics from the environment we live and grow in
48
What are examples that are both genetic variation and environmental variation?
*height *you can get calcium from food you eat but can also be tall/short through genes
49
What caused genetic variation?
*mutations
50
Describe the survival of the fittest?
*the idea that animals with more suitable characteristics to its environment would be more successful competitors and be more likely to survive
51
What is evolution?
*the idea that all of today’s species have evolved from simple life forms that first started developing over three billion years ago
52
What are four examples of selective breeding?
*domestic dogs selectively bred for their gentle nature *plants selectively bred to produce large/unusual flowers *cows selectively bred for more milk and meat *food crops bred to be resistant to disease
53
Describe process of selective breeding?
*from existing stock of animals pick ones with the characteristics that you want *breed them together *pick the offspring with your preferred characteristics and breed them together *continue process and the desirable trait gets stronger and eventually all the offspring will get the preferred characteristic
54
What are the disadvantages of selective breeding?
*if you breed closely related animals or plants then we get inbreeding *this causes breeds to be prone to disease or inherited defects
55
Describe the process of genetic engineering?
*a useful gene is isolated(cut) from one organism’s genome using enzymes *it is then inserted into a vector like a virus or bacterial plasmid *when the vector meets the target organism the gene is inserted into its cell
56
What are the pros of GM crops(genetically modified crops)
*the characteristics chosen for gm crops can increase the yield,making more food *GM crops are already being grown in some places often without any problems
57
Cons of GM crops?
* can reduce farmland biodiversity
58
How is an advantage of cloning plants?
*we are able to know what exactly the clone’s characteristics will be
59
How would you make a plant clone through cutting?
*a small piece of a plant is removed *the end is dipped in rooting powder *powder contains plant hormones and encourages the plant to develop roots *this produces a genetically identical plant to the original
60
How would you clone a plant using tissue culture?
*take plant you want to clone *divide plant into hundreds of tiny pieces *Each piece contains small number of cells which are then incubated with plant hormones *these stimulate plant to grow into a clone of original plant
61
What should the conditions for tissue culturing be ?
*sterile *in order to not introduce microorganisms like bacteria or fungi
62
How would you do embryo transplant for mammal
*sperm cells are taken from animal with characteristic we want *sperm is used to fertilise an egg *the fertilised egg develops into an embryo *glass rod is used to split the embryo into two *we transplant the two embryos into host mothers *the embryos now will grow and developand when born will form to identical offspring
63
Describe adult cell cloning?
*remove a cell from animal *remove the nucleus of the cell *take a unfertilised egg cell *remove the nucleus from the unfertilised egg cell *insert nucleus of the random cell into the empty egg cell *egg cell is given electric shock making the egg cell divide into an embryo *embryo inserted into a host mother and clone is born
64
How was the theory of natural selection developed?
*darwin went on expedition around world *he studied geology and fossils *fossils showed that plants and animals that are alive today were very similar to extinct species *he did many experiments and discussions which led to development of evolution by natural selection
65
Why was Darwin’s theory of evolution controversial and only gradually accepted?
*people strongly believed god made animals and plants and evolution didn’t back up this belief *people felt Darwin didn’t have enough evidence *people didn’t know how characteristics were inherited
66
What was Lamarck’s theory on how species changed over time?
*he suggested when a characteristic is more regularly used it becomes more developed *this strengthened characteristic is passed on to the offspring
67
What was the problem with Lamarck’s theory?
*changes that occur during an organism’s lifetime cannot be passed to the offspring
68
Why is Darwin’s theory now accepted?
*because the discovery of genetics supported his ideas
69
When does speciation occur?
*when populations of a species become so different that they can no longer successfully interbreed to make fertile offspring
70
Describe process of speciations?
*there are two populations of the same species *a physical barrier geographically isolates the two populations *conditions in both sides of the barrier are slightly different e.g dif climates *bc the environments on each side of barrier are slightly different ,dif characteristics will become more common in each population bc natural selection operating differently on the populations *eventually populations have changed sm that they won’t be able to successfully interbreed to make a fertile offspring
71
What did Mendel do?
*carried out breeding experiments on pea plants
72
What were Mendel’s discoveries?
*characteristics are determined by hereditary units *hereditary units are passed on to offspring both parents ,one unit from each parent *hereditary units can be dominant or recessive if both have dominant and recessive unit for characteristic the dominant characteristic will be expressed
73
What are fossils?
*remains of organisms from millions of years ago which are found in rocks
74
How do fossils form through gradual replacement by minerals?
*things like teeth and shells do not decay easily *they are eventually replaced by minerals as they decay forming a rock like substance shaped like the original hard part *the surrounding sediments turns to rock but the fossil stays distinct and eventually someone digs it up
75
How are fossils formed from casts and impressions?
*fossils formed when organism is buries in a soft material like clay *the clay hardens around it and the organism decays leaving a cast of itself *an animals burrow or a plants roots can be preserved as casts
76
How are fossils formed through preservation where no decay happens
*in amber and tar pits there is no oxygen or moisture for decay microbes to survive *in glaciers it’s too cold for decay microbes to work
77
When do species become extinct?
*when environment changes *new predator
78
How does antibiotic resistance happen?
*some bacteria develop mutations which make them resistant to antibiotics *so antibiotic kills most of bacteria but not the resistant ones *these resistant ones reproduce quickly and forms many resistant bacteria *this can be passed onto other people
79
How do doctors avoid too much antibiotic resistance?
* taking full course of antibiotics so all die
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