Inheritance, Variation and Evolution Flashcards
1
Q
What does asexual red production involve?
A
- Only one parent
- No fusion of gametes
- The production of genetically identical offspring (clones)
- Mitosis
2
Q
How do strawberry plants reproduce asexually?
A
Send out long shoots called runners, which touch the ground and grow a new plant.
3
Q
How do daffodils reproduce asexually?
A
Daffodils produce lots of smaller bulbs, which can grow into new plants.
4
Q
How do fungi reproduce asexually?
A
By spores
5
Q
How do malarial protists reproduce asexually?
A
When they are in the human host
6
Q
What does sexual reproduction involve?
A
The fusion of a male and female gamete.
7
Q
Which gametes fuse in animals?
A
Sperm and egg cells in animals
8
Q
Which gametes fuse in plants?
A
Pollen and egg cells
9
Q
What does sexual reproduction lead to?
A
A mix of genetic information, which produces variation in the offspring.
10
Q
What does the formation of gametes involve?
A
Meiosis
11
Q
What are the steps of meiosis?
A
1) Cell with two pairs of chromosomes (diploid cell)
2) Each chromosome replicated itself
3) Chromosomes part company and move to opposite poles
4) Cell divides for the first time
5) Copies now separate and the second cell division takes place
6) Four haploid cells each with half the number of chromosomes of the parent cell
12
Q
What happens when a cell divides by meiosis?
A
- Copies of the genetic material are made
- The cell divides twice to form four gametes
- All gametes are genetically different from one another
13
Q
Why is meiosis important?
A
Because it halved the number of chromosomes in gametes, meaning that fertilisation can restore the full number of chromosomes. Once fertilised, the resulting cell divides rapidly by mitosis and cells become specialised by differentiation.
14
Q
What are the advantages of sexual reproduction?
A
- Allows humans to selectively breed plants and animals and increase food production.
- If the environment changes, any variation means that at least some organisms will be suited and will survive.
- Produces variation in offspring.
15
Q
What are the advantages of asexual reproduction?
A
- More time and energy efficient
- Only one parent is needed
- Many identical offspring can be produced to make the best use of conditions
- Faster than sexual reproduction
16
Q
Which organisms can reproduce both sexually and asexually?
A
- Many plants e.g. using bulbs and runners
- Many fungi can make spores by sexual and asexual reproduction
- Malaria parasites reproduce sexually in the mosquito as well as asexually in humans.
17
Q
Would organisms reproduce sexually or asexually if they had a choice?
A
Reproduce asexually when conditions are good to make a lot of well-suited offspring. Sexual reproduction is used when conditions are getting worse.
18
Q
What is genetic material?
A
Genetic material in nucleus is made of DNA which is contained in chromosomes.
19
Q
What is a gene?
A
A small section of DNA on a chromosome.
20
Q
What does each gene code for?
A
A particular sequence of amino acids, to make a specific protein.
21
Q
What is a genome?
A
The genome of an organism is its entire genetic material
22
Q
Why is research into the genome useful?
A
- Doctors can search for genes linked to different types of disorder
- It can help scientists to understand the cause of inherited disorders and how to treat them
- Scientists can investigate how humans may have changed overtime and even how ancient populations have migrated across the globe
23
Q
What are the choices offered to people about genomes now?
A
A person now has the choice to have their genome tested to see how likely it is that they may get a certain disorder.
24
Q
What is DNA?
A
A polymer made up of repeating units called nucleotides.
25
What does each nucleotide consist of?
- A sugar
- A phosphate
- One of four bases: A, C, G or T
26
What does each nucleotide have?
Each molecule has two alternating sugar and phosphate strands which are twisted to form a double helix. Attached to each sugar is one of the four bases.
27
Which of the bases are attracted which means that the strands in a nucleotide holds together?
A C on one strand always link with a G in the opposite strand
A T on one strand always links with an A on the opposite strand
28
What does the order of DNA control?
The order in which amino acids are joined together to make a particular protein.
29
What is the code for one amino acid?
A sequence of three bases
30
What are proteins synthesised on?
Ribosomes using a template that has been taken from the DNA and carried out of the nucleus.
31
How does a protein chain grow?
Carrier molecules bring specific amino acids to add to the growing protein chain in the correct order.
32
What happens when a protein chain is finished?
It folds up to form a unique shape which allows the proteins to do their jobs as enzymes, hormones or structural proteins such as collagen.
33
What is a mutation?
A change in DNA
34
What happens if any bases in DNA are changed?
The order of amino acids in the protein coded for by the gene may be changed.
35
What do mutations occur?
All the time. Most do not alter the protein or only alter it slightly so it still works.
36
What are some characteristics controlled by?
A single gene e.g. fur colour in mice and red-green colour blindness in humans.
37
What is an allele?
A different form of a gene.
E.g. the gene for the attachment of earlobes had two alleles - attached or free.
38
An individual always has two alleles for each gene:
- one allele from mother
| - one allele from father
39
What is a genotype?
The combination of alleles present in a gene.
E.g. bb
40
What is the phenotype?
How the alleles are expressed e.g. blue eyes.
41
What can alleles be?
Dominant or recessive
42
What does homozygous mean?
If two alleles present are the same, the person if homozygous for that gene e.g BB or bb
43
What does heterozygous mean?
If the two alleles are different e.g. Bb
44
Which sort of allele is always expressed?
A dominant allele even if one copy is present. A recessive allele is only expressed if two copies are present e.g. no dominant allele is present.
45
What are most characteristics controlled by?
Several genes working together.
46
What is mono hybrid inheritance ?
If only one gene is involved in coding for a characteristic.
47
What can be used to predict the outcome of a mono hybrid cross?
Punnet squares
48
Information on punnet squares:
These diagrams use capital letters for dominant alleles and lower case letters for recessive alleles.
For example:
The allele for a free earlobe is dominant so E can be used.
The allele for an attached earlobe is recessive so e can be used
49
A few mutations may cause the protein to have a different shape:
- If it is an enzyme the substrate may no longer fit into the active site.
- If it is a structural protein it may lose its strength.
50
Not all parts of DNA code for proteins:
- Non coding parts of DNA can switch genes on and off so that they can/cannot make specific proteins.
- Mutations in these areas of DMA may affect home genes are expressed.
51
What can increase the rate at which mutations occur?
Certain chemicals and high energy radiation.
52
What mutations occur occasionally?
Mutations that are useful, without this type of variation evolution by natural selection would not occur.
53
Until the 19th century what did most people think that sexual reproduction produced?
A blend of characteristics- Gregor Mendel investigated this bu carrying out breeding experiments on pea plants.
54
What did Gregor Mendel discover about the outcome of sexual reproduction?
That characteristics are determined by ‘units’ that are inherited and do not blend together.
55
What did scientists realise in the early 20th century?
That chromosomes and Mendel’s units behaved in similar ways. They decided that the ‘units’ now called genes were located on chromosomes.
56
What did scientists work out in the mid 20th century?
What the structure of DNA looked like and the mechanism by which genes work.
57
Why was the the importance of Mendel’s discovery not recognised during his lifetime?
- He was a monk in a monastery, not a scientist at a university.
- He did not publish his work in a well known book or journal.
58
What is variation?
Difference in the characteristics of individuals in a population.
59
Variation may be due to differences in:
- genetics
- conditions in which individuals have developed (environment)
- Combination if genes and environment.
60
What does sexual reproduction produce?
A different combination of alleles and therefore, variation, but sometimes mutations create new alleles.
61
What are the effects of mutations?
Most mutations do not affect the phenotype, a small number do. Within these, very rarely, a mutation may produce a phenotype that gives an organism a great survival advantage.
62
What is evolution?
The gradual change in the inherited characteristics of a population over time. This may lead to the formation of a new species.
63
What is natural selection and who put it forward?
Charles Darwin and it states that all species have evolved from simple life forms that first developed more than 3 billion years ago.
64
What did Darwin observe during his round-the-world expedition?
- Organisms often produce large numbers of offspring.
- Populations usually stay about the same size.
- Organisms are slightly different, they show variation.
- Characteristics can be inherited.
65
What conclusions did Darwin’s observations lead to?
- There is a struggle for existence
- More organisms are born that can survive
- The ones that survive and breed are the ones best suited to the environment
- They pass on their characteristics of populations change
66
What did Alfred Russel Wallace suggest in 1858?
A similar theory to Darwin and this made Darwin realise that he should publish his ideas.
67
What are genetic disorders?
Inherited human disorders caused by the inheritance of certain alleles.
68
What is polydactyly?
A genetic disorder having extra fingers or toes.
69
What is polydactyly caused by?
A dominant allele and can be passed on by only one parent who has the disorder, is heterozygous.
70
What is cystic Fibrosis?
A genetic disorder that causes thick and sticky mucus to coat the lungs, gut and pancreas.
71
What is cystic fibrosis?
Caused by a recessive allele, disorder if the cell membranes, parents may be a carrier of the disease but not have it, sufferer must be homozygous recessive.
72
What is it now possible to do in terms of genetic disorders?
To test unborn foetuses for a range of genetic disorders. However, this means that the parents may have to make a difficult decision about the future if their baby. Only a small risk to the pregnancy when removing foetal cells to test.
73
How many chromosomes in the body carry the genes that determine sex?
Only one pair out of the 23 pairs in the human body. These are called the sex chromosomes.
74
What are the sex chromosomes like in females?
They are identical and are called X chromosomes (XX)
75
What are sex chromosomes like in males?
Males inherit an X chromosome and a much shorter chromosome called a Y chromosome (XY)
76
As with all chromosomes, what do offspring inherit?
- One sex chromosome from the mother (X)
| - One sex chromosome from the father ( X or Y)
77
When did Darwin publish his theory in a book called ‘on the origin of species’?
1859
78
Why was there a lot of controversy over Darwin’s?
- Theory challenges religion
- Not enough evidence at the time the theory was published to convince many scientists
- Mechanism of inheritance and variation was not known until 50 years after the theory was published.
79
What was the other theory of evolution proposed by Jean-Baptiste Lamarck?
His theory was based on the idea that changes can occur in an organism during its lifetime can be inherited. We know that, in most cases, this type of inheritance cannot occur.
80
What is one problem with Darwin’s theory?
It has been solved- we now know the mechanism of inheritance and variation e.g. what characteristics are passed in to offspring in genes.
81
How do fossils provide evidence for evolution?
Fossils may be formed in various ways:
- From the hard parts of animals that do not decay easily.
- From parts of organisms that have not decayed, because one of more of the conditions needed for decay was absent.
- When parts of the organisms are repacked by other materials as they decay.
- As preserves traces of organisms e.g. footprints.
82
How have scientists used fossils to see evolution?
To look at how organisms have gradually changed over time.
83
Why are there gaps in fossil records?
- Many early forms of life were soft-bodied, which means they have left very few traces behind.
- Traces may have been destroyed by geological activity.
84
How can the development of anti biotic resistant strains of bacteria be explained using the theory of natural selection?
Bacteria can evolve rapidly because they reproduce at a fast rate.
When they reproduce mutations occur
Some mutated bacteria might be resistant to antibiotics and are not killed.
These bacteria survive and reproduce so a resistant strain develops.
85
What is selective breeding?
The process by which humans breed plants and animals for particular genetic characteristics. Humans have been doing this for thousands of years since they first bred food crops from wild plants and domesticated animals.
86
What are the steps of selective breeding?
1) Choose parents that best show the desired characteristics.
2) Breed then together.
3) From the offspring again choose those with desired characteristics.
4) Continue over many generations.
87
What are the type of characteristics usually selected for selective breeding?
- Disease resistance in food crops
- Animals that produces more milk/meat
- Domestic dogs with a gentle nature
- Large or unusual flowers
88
What can selective breeding sometimes lead to?
‘Inbreeding’ where some breeds are particularly prone to disease/ inherited defects.
89
What is genetic engineering?
A more recent way of bringing about changes in organisms.
90
What does genetic engineering involve?
Changing the characteristics of an organism by introducing a gene from another organism.
91
In genetic engineering:
1) Enzymes are used to isolate the required gene.
2) This gene is inserted into a vector.
3) The vector is used to insert the gene into the required cells.
(If the genes are put into the cells at the egg or embryo stage then all cells in the organisms will get the new gene).
92
Plant crops have been genetically engineered to:
- Be resistant to diseases, insects or herbicide attacks.
| - Produce bigger, better fruits.
93
What are crops that have had their genes modified by genetical engineering called?
Genetically modified crops/ GM crops
94
Why are some people concerned about GM crops?
That there are possible long term effects on population if wild flowers, insects and human health (if consumed).
95
What are other ethical issues of genetic engineering?
The role that multinational companies pay in manufacturing GM crops and setting the price.
96
What have fungi/bacteria cells been genetically engineered to do?
Produce useful substances.
97
What may genetic modification be useful for in the future?
To cure/ prevent diseases.
98
What are clones?
Genetically identical individuals
99
How are clones produced?
By asexual reproduction
100
What are some ways of making clones in plants?
Cuttings - methods used by gardeners
Tissue cultures - uses a small group of cells to grow new plants, used commercially and to preserve rare plant species.
101
How can clones be produced in animals?
By splitting apart cells from an embryo before they become specialised, then transplanting identical embryos into host mothers.
102
How can clones be produced using adult cells?
- Remove nucleus from unfertilised egg cell.
- Insert nucleus from an adult body cell from an organism you want to clone into the empty egg cell.
- stimulate egg cell to divide using an electric shock.
- Allow the resulting embryo to develop into a ball of cells
- Insert the embryo into the womb of a surrogate female.
103
How have living things been classified traditionally?
Into groups based on their structure and characteristics.
104
Who was one of the main systems of classification developed by?
Carl Linnaeus
105
How did Linnaeus classify living things?
```
Kingdom
Phylum
Class
Order
Family
Genus
Species
```
106
How are organisms named?
By the binomial system e.g. they have two parts to their Latin name:
First part- Genus
Second part- Species
107
Why were new models of classification proposed?
- Microscopes improves
| - Biochemical processes became better understood
108
What is the current classification system?
A three-domain system developed by Carl Woese.
109
What are organisms divided into in the three-domain system?
- Archaea (primitive bacteria, usually living in extreme environment)
- Bacteria
- Eukaryota (including protists, fungi, plants and animals)
110
What may extinction be caused by?
```
Changes to the environment
New predators
New diseases
New, more successful competitors
A single catastrophic event
```
111
What are evolutionary trees?
Method used by scientists to show how they think organisms are related. They use current classification data for living organisms and fossil data for extinct organisms.
112
Who proposed a theory of specification?
Alfred Wallace
113
What did Alfred Wallace’s theory of specification say (how new species develop)?
1) Populations become physically isolated from each other.
2) Genetic variation is present between the two populations.
3) Natural selection operates differently in the two populations.
4) The populations become so different that successful inbreeding is no longer possible.
114
What is variation?
Difference in the characteristics of individuals in a population.
115
Variation may be due to differences in:
- genetics
- conditions in which individuals have developed (environment)
- Combination if genes and environment.
116
What does sexual reproduction produce?
A different combination of alleles and therefore, variation, but sometimes mutations create new alleles.
117
What are the effects of mutations?
Most mutations do not affect the phenotype, a small number do. Within these, very rarely, a mutation may produce a phenotype that gives an organism a great survival advantage.
118
What is evolution?
The gradual change in the inherited characteristics of a population over time. This may lead to the formation of a new species.
119
What is natural selection and who put it forward?
Charles Darwin and it states that all species have evolved from simple life forms that first developed more than 3 billion years ago.
120
What did Darwin observe during his round-the-world expedition?
- Organisms often produce large numbers of offspring.
- Populations usually stay about the same size.
- Organisms are slightly different, they show variation.
- Characteristics can be inherited.
121
What conclusions did Darwin’s observations lead to?
- There is a struggle for existence
- More organisms are born that can survive
- The ones that survive and breed are the ones best suited to the environment
- They pass on their characteristics of populations change
122
What did Alfred Russel Wallace suggest in 1858?
A similar theory to Darwin and this made Darwin realise that he should publish his ideas.
123
What are genetic disorders?
Inherited human disorders caused by the inheritance of certain alleles.
124
What is polydactyly?
A genetic disorder having extra fingers or toes.
125
What is polydactyly caused by?
A dominant allele and can be passed on by only one parent who has the disorder, is heterozygous.
126
What is cystic Fibrosis?
A genetic disorder that causes thick and sticky mucus to coat the lungs, gut and pancreas.
127
What is cystic fibrosis?
Caused by a recessive allele, disorder if the cell membranes, parents may be a carrier of the disease but not have it, sufferer must be homozygous recessive.
128
What is it now possible to do in terms of genetic disorders?
To test unborn foetuses for a range of genetic disorders. However, this means that the parents may have to make a difficult decision about the future if their baby. Only a small risk to the pregnancy when removing foetal cells to test.
129
How many chromosomes in the body carry the genes that determine sex?
Only one pair out of the 23 pairs in the human body. These are called the sex chromosomes.
130
What are the sex chromosomes like in females?
They are identical and are called X chromosomes (XX)
131
What are sex chromosomes like in males?
Males inherit an X chromosome and a much shorter chromosome called a Y chromosome (XY)
132
As with all chromosomes, what do offspring inherit?
- One sex chromosome from the mother (X)
| - One sex chromosome from the father ( X or Y)
133
When did Darwin publish his theory in a book called ‘on the origin of species’?
1859
134
Why was there a lot of controversy over Darwin’s?
- Theory challenges religion
- Not enough evidence at the time the theory was published to convince many scientists
- Mechanism of inheritance and variation was not known until 50 years after the theory was published.
135
What was the other theory of evolution proposed by Jean-Baptiste Lamarck?
His theory was based on the idea that changes can occur in an organism during its lifetime can be inherited. We know that, in most cases, this type of inheritance cannot occur.
136
What is one problem with Darwin’s theory?
It has been solved- we now know the mechanism of inheritance and variation e.g. what characteristics are passed in to offspring in genes.
137
How do fossils provide evidence for evolution?
Fossils may be formed in various ways:
- From the hard parts of animals that do not decay easily.
- From parts of organisms that have not decayed, because one of more of the conditions needed for decay was absent.
- When parts of the organisms are repacked by other materials as they decay.
- As preserves traces of organisms e.g. footprints.
138
How have scientists used fossils to see evolution?
To look at how organisms have gradually changed over time.
139
Why are there gaps in fossil records?
- Many early forms of life were soft-bodied, which means they have left very few traces behind.
- Traces may have been destroyed by geological activity.
140
How can the development of anti biotic resistant strains of bacteria be explained using the theory of natural selection?
Bacteria can evolve rapidly because they reproduce at a fast rate.
When they reproduce mutations occur
Some mutated bacteria might be resistant to antibiotics and are not killed.
These bacteria survive and reproduce so a resistant strain develops.
141
What is selective breeding?
The process by which humans breed plants and animals for particular genetic characteristics. Humans have been doing this for thousands of years since they first bred food crops from wild plants and domesticated animals.
142
What are the steps of selective breeding?
1) Choose parents that best show the desired characteristics.
2) Breed then together.
3) From the offspring again choose those with desired characteristics.
4) Continue over many generations.
