variations inheritance and evolution Flashcards
(119 cards)
1
Q
what is asexual reproduction?
A
asexual reproduction is when something produces with only one parent-no gametes are involved
2
Q
does asexual reproduction have variation? and why?
A
no all of offspring are identical clones as there is no mixing of genetic material
3
Q
how is asexual reproduction achieved?
A
for eukaryotic such as plants and fungi this process is done through mitosis
for prokaryotes such as bacteria this is done through binary fission
4
Q
which form of reproduction do we associate with mitosis?
A
asexual
5
Q
which form of reproduction do we associate with meiosis?
A
sexual
6
Q
give an example of 3 species that use asexual reproduction?
A
daffodils
strawberries
brambles
7
Q
what is sexual reproduction?
A
reproduction which involves the fusion of male and female gametes-fertilisation will occur
8
Q
does variation arise in sexual reproduction and why?
A
yes-offspring will contain a mixture of parents genes-23 chromosomes from each parent-inherit characteristics -genetically different-variation arises
9
Q
give an example of gametes in animals and plants?
A
animals-sperm and egg cells
plants-pollen and eggs in flowering plant
10
Q
how many chromosomes does a gamete have?
A
23-only has half the genetic material of a normal cell-when two gametes fuse together the resulting cell will have 46 chromosomes
11
Q
What is a clone? Give an example
A
A genetically identical organism/cell
e.g. identical twins
bacteria
12
Q
state 3 differences between sexual and asexual reproduction?
A
1.sexual reproduction involves two parent cells whereas asexual reproduction only involves one parent cell
2.sexual reproduction will result in genetically different offspring as they inherit characteristics from both parents whereas asexual reproduction will produce clones/genetically identical offspring
3.gametes are involved in sexual reproduction whereas asexual reproduction does not involve gametes
13
Q
what is a benefit of asexual reproduction?
A
only one parent is needed-process is very quick
14
Q
what is a drawback of asexual reproduction?
A
-all the offspring are clones-no genetic variation-new diseases will damage/kill all offspring-wipe out entire population
-less chance of adapting to new conditions
15
Q
what is 2 benefits of sexual reproduction?
A
short term-loads of genetic variation within population-less likely to get wiped out by single event
long term-population can adapt to changing conditions-allows for evolution to take place
16
Q
what is a drawback of sexual reproduction?
A
takes a lot more time and energy-animals have to first find a potential mate
17
Q
what is a chromosome?
A
chromosomes are found in the nucleus of any cell and contain genetic information
18
Q
how many chromosomes do we have in our bodys?
A
we have 23 pairs of chromosomes in almost every cell of our body-one pair from mother and one pair from father
46 chromosomes
19
Q
What do we call the 23rd pair of chromosomes?
A
sex chromosomes-determine your biological gender
20
Q
what is the chromosomes for a female and male
A
XX-female
XY-male
21
Q
what is meiosis?
A
cell division that forms gametes (sperm and egg cells)
22
Q
how many divisions is there in meiosis?
A
2 divisions-forms 4 gametes/daughter cells
23
Q
how many chromosomes do the gametes have?
A
gametes have half the number of chromosomes-23
24
Q
describe how meiosis takes place? (5 stages)
A
1.all of the cells dna is replicated-replicating chromosomes
2.the two armed chromosomes all line up along the center of the cell in their pairs
3.the chromosome pairs are pulled apart and the whole cell splits into two-chromosomes are randomly distributed
4.now a second division will take place-chromosomes all line up again along center of cell-2 arms of each chromosome are pulled to opposite sides of the cell
5.the cells divide in half again-producing 4 genetically unique daughter cells/gametes
25
what is the cell cycle?
when a cell divides in a series of stages
26
describe the 3 stages in the cell cycle?
1.growth and dna replication-begins with cell growth-number of organelles in the cells increases-eg ribosomes-next genetic material copies/doubles-DNA replication
2.mitosis-the copied chromosomes separate and the nucleus divides into two
3.the cell divides to form 2 new identical cells
27
describe how mitosis takes place?
1.cell grows and increases organelles eg ribosomes
2.the dna is duplicated and forms chromosomes
3.the chromosomes line up at the center of the cell and fibres pull them apart to opposite poles of the cell
4.membrane forms around the chromosomes and the nucleus divides
5.lastly the cytoplasm divides and two new genetically identical daughter cells are produced
28
what is the purpose of mitosis?
-allows cells to grow and develop
-replaces damaged cells
29
give two similarities of mitosis and meiosis?
-they are both forms of cell division
-both involve dna replication
30
give three differences between mitosis and meiosis?
-meiosis occurs in the testes and ovaries whereas mitosis occurs in all other body cells
-meiosis produces 4 daughter cells whereas mitosis produces two daughter cells
-meiosis produces cells with half the number of chromosomes whereas mitosis produces cells with the same chromosome number as the parent cell.
31
exam style
describe the type of cell division that produces gametes? (3marks)
-the cell division that produces gametes is meiosis
-meiosis has two cell divisions which occur in the either the ovaries or testes
-meiosis will produce 4 daughter cells with variation
32
what is a gene?
a gene is a length of dna that contains a code that regulates the proteins that are made in the body
code for sequence of amino acids-makes proteins
codes for a characteristic
33
what is DNAs structure?
dna is a polymer-a large molecule made up of many small repeating units joined together
dna is formed of two strands which form a double helix
made up of 46 chromosomes
34
why is DNA shaped like a double helix?
makes it a compact structure that fits into the nucleus of a cell
35
what is the role of dna/what does it do?
DNA determines which proteins the cell produces-determine what type of cell it will be
36
what does DNA stand for?
Deoxyribose nucleic acid
37
what is a genome?
a genome is the entire set of dna of an organism
38
how has mapping the genome helped science? (3)
-identify genes that are linked to certain diseases
-more understanding and better treatment of inherited disorders
-understand human migration and evolution
39
how many different types of amino acids is there?
20-makes 1000s of different proteins
40
what is a chromosome in terms of dna?
a tightly wound molecule containing our genes
41
what are alleles?
different versions of the same gene
42
define homozygous and give an example?
an organism with 2 identical alleles for a gene eg BB or bb
43
define heterozygous and give an example?
an organism with 2 different alleles for a gene eg Bb
44
What is a genotype?
your combination of alleles e.g. TT/tt/Tt
entire collection of alleles we have
45
what is a phenotype?
the characteristics you get from your genotype
46
what is the chance of your offspring being a girl or boy? and why?
50 % because Each parent donates 50% of the offspring's alleles. The female always contributes an X chromosome, whereas the male has a 50/50 chance of contributing either an X or a Y chromosome
47
what will a dominant allele do?
a dominant allele will always show even if the individual only has one copy of the allele
48
when does a recessive allele show?
a recessive allele only shows if the individual has 2 copies of the recessive allele eg bb
49
how can two parents who do not have any alleles for polydactyly have a child with polydactyly?
-a mutation occurs during meiosis
-causes a change in amino acid sequence
-causing a different specific protein to be produced
-may cause polydactyly
50
what is an inherited disorder?
a group of conditions passed on in alleles/inherited from parents
51
what are the two main inherited disorders?
-polydactyly
-cystic fibrosis
52
what is polydactyly?
when a child is born with extra fingers or toes
53
what type of allele is polydactyly caused by?
a dominant allele eg Aa
54
what is cystic fibrosis?
a disorder of the cell membranes-causing abnormally thick mucus
55
what type of allele is cf caused by?
a recessive allele eg ff
56
what is a carrier?
somebody who doesn't have the condition themselves but could potentially pass it on as they have one of the alleles for the condition eg heterozygous for cf
57
what will a change in the amino acid sequence cause?
a different specific protein to be produced
58
what is embryo screening?
embryos can be tested for the presence of a genetic disorder-can be used by couples who carry genes linked with inherited disorders
59
what are the benefits of embryo screening?
-reduce overall suffering-fewer people with health problems
-saves money treating genetic disorders is really expensive
60
what are the drawbacks of embryo screening?
-implies that people with genetic disorders are undesirable-social issue-increases prejudice
-future screening for other traits-designer babies
-can increase risk of miscarriage
-ivf is an physically and emotionally stressful procedure
61
what is genetic engineering?
modifying an organism's genome by transferring a desired gene from another organism to a different one
62
how/why have we genetically modified bacteria?
to produce the hormone insulin-harvest it and treat diabetes
63
give the method for genetic engineering? (5 steps)
1.the desired characteristic is selected
2.enzymes are used to isolate the required gene and to cut the gene out of the chromosome
3.this gene is then inserted into a vector eg bacterial plasmid/virus
4.the vector inserts the gene into required cells
5.the genes are transferred to animal/plant or microorganisms cells during early development-allows them to develop with required characteristics
64
what are the benefits of genetic engineering?
plants
-could reduce food shortages
-crops often have a higher yield
-more profit for farmers
-may be used in future to treat inherited disorders
65
what are the drawbacks of genetic engineering?
-long term effects of eating gm food is unknown
-toxins in gm plants can affect pollinators
-ethical concerns-could impact food chains
-less variation
66
what is the theory of evolution?
all species of living things have evolved from simple life forms that first developed more than 3 billion years ago
67
What do you need to carry out genetic engineering?
Desired DNA/gene
Enzymes
Host to put the gene in
68
what process drives evolution?
natural selection
69
define variation
differences in the characteristics within a species-caused by genes and the environment
70
what is genetic variation caused by?
mutations
71
what is a mutation?
a mutation is a change to a gene-change in dna code-protein may be different-these happen randomly and continuously-most mutations have no effect on an organisms phenotype
72
What might happen if 2 population of one species become so different from each other?
A new species develops – they can no longer interbreed and make fertile offspring
73
what do genes code for?
amino acid sequence-proteins
74
what two factors impact our phenotype?
genes and our environment
75
who observed/discovered natural selection?
charles darwin-survival of the fittest
76
what is the idea of natural selection?
when the fittest individuals are selected to survive/more likely to survive and breed and pass on genes to offspring
77
define evolution?
inheritance of certain characteristics in a population,over multiple generations,could lead to a change in the whole species
78
who discovered evolution?
charles darwin
79
what proved Darwin's theories?
-antibiotic resistance bacteria
-fossil records
80
what were Darwin's 4 main ideas?
1.populations show a wide range of variation (caused by mutations)
2.some individuals are better suited to their environment than others
3.individuals who are the most suited to the environments are more likely to survive and breed successfully
4.the genes for the useful characteristics will be passed on to the next offspring
81
explain how natural selection has led to giraffes having long necks (4)
1.a mutation has caused variation in giraffe neck length
2.there is competition for food and giraffes who have longer necks are better suited as they can reach food higher up in trees
3.giraffes with longer necks are more likely to survive and breed successfully
4.survivors pass on the gene for long necks to offspring-over many generations this leads to all giraffes having long necks
82
what is a species?
a species is organisms that are similar enough to be able to breed and produce fertile offspring
83
give 3 examples of characteristics you inherit from your genes?
-blood type
-eye colour
-ethnicity
84
give 3 examples of characteristics you gain from your environment?
-accent
-diet
-piercings
85
what is selective breeding?
Humans deliberately breeding plants or animals together or particular characteristics to produce offspring with specific characteristics
86
what is the general process of selective breeding? (4 steps)
1.parents with desired characteristics are chosen
2.they are bred together
3.offspring with desired characteristics are bred together
4.repeated over many generations
87
What characteristics might be selectively bred?
Animals for high milk yield or meat yield
Disease resistance crops
Dogs with gentle temperament
decorative flowers eg large or unusual flowers
88
explain how a farmer could carry out selective breeding to ensure their cows produced lots of milk? (3 marks)
1.farmer selects a female cow who produces a lot of milk and a male cow whose mother produced lots of milk
2.the parent cows are bred together
3.the offspring cows which produce lots of milk are selected and bred
4.this is repeated over many generations until all female cows produce lots of milk
89
what are the benefits of selective breeding?
-reduces food shortages
-can be used to breed guide dogs with a gentle nature
-can increase crops yield/resistance to diseases-more food
90
what are the drawbacks of selective breeding?
-reduces gene pool of population-best individuals are closely related-inbreeding
-prone to diseases and inherited disorders
91
define a gene pool?
collection of different alleles in a population
92
Give an example of something that is genetically engineered?
insulin
93
What type of organism carries out decay?
micro-organism-respire as they break down organic matter-releases co2
94
What evidence do we have for evolution?
fossils
95
explain how antibiotic resistance arises? (6 steps)
1.a mutation occurs in the genes of bacterial cells
2.the mutation stops the bacterial cell being killed by the antibiotic
3.these bacteria are now deemed resistant
4.bacteria without the mutation die or cant reproduce when in contact with antibiotic
5.resistant bacteria face less competition from normal bacteria and reproduce
6.the resistant population grows
96
what do we call bacteria that are resistant to loads of different types of antibiotic? give an example
superbugs eg mrsa
97
how can we prevent antibiotic resistance? (5)
-doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections
-Treat specific bacteria with specific antibiotics.
-High hospital hygiene levels, including regular hand washing by staff and visitors.
-Patients who are infected with antibiotic resistant strains of bacteria should be isolated from other patients.
-those infected with bacterial infections should isolate-wont pass it on-less demand for antibiotics
-complete full course of antibiotics-ensures all bacteria are killed and none become resistant
98
why is antibiotic resistance such a problem?
-we use so many antibiotics that resistance is bound to arise-due to farming-difficult to develop new antibiotics which bacteria aren't resistant to-may be unable to treat infections-could be deadly
99
what are fossils?
remains of organisms from many years ago-found in rocks-provide evidence of life-shows how species have evolved
100
give three ways fossils can form?
-gradual replacement by minerals
-casts and impressions
-preservation
101
Given an example of an environment where no decay might occur so full preservation of a fossil might occur
Amber – lack oxygen
Glaciers – too cold
Peat bogs – too acidic
102
how does gradual replacement by mineral form fossils?
1.body parts like bones teeth and shells decay really slowly
2.over time they are gradually replaced by minerals as they decay
3.slowly forms rock like substances-exact same shape and size of original structure
103
how do casts and impressions form fossils?
1.organism is buried in a soft material eg clay
2.as the clay hardens the organism decays-leaving a cast
104
how does preservation form fossils?
1. no decay happens-conditions aren't right-need o2,moisture and perfect temp and ph for enzymes to work properly
2.decay wont take place
3.preserves organism
105
why is there so many different theories of when life began/lack of evidence?
-early life forms were soft bodied-decayed quickly-didn't form fossils-lack of evidence
-fossils formed so long ago-destroyed since by geological events-movement of tectonic plates or volcanoes
106
define extinction?
when there are no remaining members of that species alive
107
give 5 reasons/factors for extinction?
-environment changes too quickly-global warming
-new predator-kills them all
-new disease-wipes out population
-new species outcompetes them-eg for food
-catastrophic event eg meteor
108
Name the 3 domain groups?
-Archaea (primitive bacteria usually living in extreme environments)
-Bacteria (true bacteria)
-Eukaryota (which includes protists, fungi, plants and animals).
109
What is classification?
Organising organisms into groups based on similarities/characteristics they have
110
Who proposed the 3 domain classification system?
carl woese
111
Why was the 3 domain classification system introduced?
When further information became available e.g. information on DNA/biochemical processes/internal structures
112
Why is the binomial system helpful?
Common language used by all scientists
No confusion
Used worldwide
113
Who developed to first classification system (in 1700s)?
Carl Linnaeus
114
what is the genus?
the first name-not shared with other species
115
what is the species?
the surname-shared with other species
116
what is the binomial name made up of?
genus and species
117
What does an evolutionary tree show?
Relationships between organisms
Shows common ancestors
And how closely related different species are with one another
118
give the linean classification system?
domain-prokaryote/eukaryote/archaea
kingdom-plant/animal
phylum
class
order
families
genus
species
119
mnemonic for classification system?
dreary
king
philip
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