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Biology > Inheritance, variation and evolution. > Flashcards

Inheritance, variation and evolution. Flashcards

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1
Q

What does asexual reproduction involve?

A

-Only one parent.
-No fusion gametes so no mixing of genetic information.
-Produce identical offspring (clones).

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2
Q

How do strawberry plants reproduce asexually?

A

They send out long shoots called runners which touch the ground and grow a new plant.

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3
Q

What does sexual reproduction involve?

A

-The fusion of male and female gametes:
-Sperm and egg cells in animals
-Pollen and egg cells in flowering plants.
-Mix of genetics which produces variation in the offspring.
-Involves meiosis.

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4
Q

Meiosis.

A

When a cell divides by meiosis:
-Copies of the genetic information are made.
-Cell divides twice to form 4 gametes each with a single set of chromosomes (23).
-Fetilastion restores the full number of chromosomes.
-Once fertilisation the resulting cell divides rapidly by mitosis- cells specialise via differentiation.

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5
Q

Advantages of sexual reproduction.

A

-Produces variation in the offspring.
-If the environment changes any variation means that some organisms will be suited and can survive.
-Allows humans to selectively breed animals and plants and increase food production.

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6
Q

Advantages of asexual reproduction.

A

-Only one parent is needed.
-More time and energy efficient- need to find a mate.
-Faster than sexual reproduction.
-Many identical offspring are produced to make the best use of good conditions.

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7
Q

What is the genome of an organism?

A

It is the entire genetic material.

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8
Q

How does studying the human genome help scientists?

A

-Search for genes linked to different types of disorders.
-Understand the cause of inherited diseases and how to treat them.
-How humans have changed over time.

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9
Q

Is DNA a polymer or a monomer?

A

Polymers are made up of repeating units called nucleotides.

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10
Q

What does each nucleotide consist of?

A

-A sugar, a phosphate and one of four bases A,C,G or T.

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11
Q

What do nucleotides join to form?

A

Join to form long strands. Each molecule has 2 alternating sugar and phosphate stands which twist to form a double helix.
-Attached to each sugar is one of the 4 bases.

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12
Q

It is an attraction between the different bases that hold two strands together:

A

-a C on 1 strand always links with a G on the opposite strand.
-a T on 1 strand always links with an A on the opposite strand.

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13
Q

How many bases are there in one amino acid?

A

3.

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14
Q

How are proteins made?

A

-Proteins are synthesised in ribosomes using a template taken from the DNA- turned into a single strand of mRNA which is carried tothe nucleus to cytoplasm.
-Carrier molecules (tRNA) then bring specific amino acids to add to the growing protein chain in the correct order.
-It then folds up to form a unique shape.
-Allows the proteins to do their jobs as enzymes. hormones or structural proteins.

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15
Q

What happens if the bases in a DNA change?

A

Then it may change the order of the amino acids in the protein coded for by the gene. Only changes slightly so it still works.

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16
Q

What happens when the protein mutates (shape)?

A

-If it’s an enzyme then the substrate may no longer fit into the active site.
-If it’s a structural protein, it may lose its strength.

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17
Q

Not all parts of DNA code for proteins:

A

-Non-coding parts of DNA can switch genes on/off so that they can/cannot make specific proteins.
-Mutations in these areas of DNA may affect how genes are expressed.

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18
Q

What did Gregor Mendel investigate?

A

That sexual reproduction produced a blend of characteristics. He investigated this by carrying out breeding experiments on pea plants.

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19
Q

What did Mendel discover?

A

That characteristics are determined by units (now called genes) that are inherited and do not blend together.

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20
Q

What are alleles?

A

Different forms of genes. One from each parent.

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21
Q

What is the combination of alleles present in a gene called?

A

Genotypes.

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22
Q

What are the alleles called when their characteristics appear?

A

Phenotype.

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23
Q

What are the two types of alleles?

A

Dominant and recessive.

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24
Q

What is a person called if they have 2 of the same alleles?

A

Homozygous. Eg BB or bb

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25
Q

What is a person called if two of the alleles are different?

A

Heterozygous. Eg Bb.

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26
Q

What is it called when only one gene is involved?

A

Monohybrid inheritance.

27
Q

What is used to predict the outcome of a monohybrid cross?

A

Punnet squares.

28
Q

What do punnet squares use?

A

Capital letters for dominant alleles and lowercase letters of recessive alleles.

29
Q

Polydactly.

A

Having extra fingers or toes. Caused by a dominant allele.

30
Q

Cystic fibrosis.

A

A disorder of cell membranes. Caused by a recessive allele..

31
Q

What are the two female chromosomes?

A

XX.

32
Q

What are the two male chromosomes?

A

XY.

33
Q

What do offspring inherit?

A

An X chromosome from their mother and an X or Y chromosome from their father.

34
Q

What is variation?

A

The differences between the individuals in a species.

35
Q

What differences might variation be due to?

A

-The genes individuals have inherited (genetics).
-The conditions in which individuals have developed (environment).
-A combination of both genetic and environmental factors.

36
Q

What creates new alleles?

A

Mutations. However, only a small number affect the phenotype.

37
Q

What is evolution?

A

It is the gradual change in the inherited characteristics of a population over time.

38
Q

What is the theory that most scientists support?

A

Natural selection which was put forward by Darwin.

39
Q

What does natural selection state?

A

That all species have evolved from simple life forms that first developed more than 3 billion years ago.

40
Q

What did Darwin
observe and conclude?

A

He observed that organisms have lots of offspring, and the population stays the same size and characteristics can be inherited.
He concluded that there is a struggle for existence, more organisms are born than can survive and the ones that survive are best fitted to the environment.

41
Q

How can fossils be formed?

A

-From the hard parts of animals that do not decay easily.
-From parts of organisms that haven’t decayed because one or more conditions needed for decay were absent.
-When parts are replaced due to decay.
-Preserved traces of organisms.

42
Q

Why are there gaps in the fossil fuel records?

A

-Many early forms of life were soft bodies so little to no traces were left behind.
-Traces might have been destroyed by geological activity.

43
Q

How can antibiotic restraints be explained using the theory of evolution?

A

-Bacteria can evolve rapidly as they reproduce at a fast rate.
-When they reproduce, mutations occur.
-Some mutated bacteria are resistant to antibiotics and are not killed.
-These survive and a resistant strain develops.

44
Q

How can extinction be caused?

A

it can be caused by:
-Changes to the environment over long periods of time
-New predators
-New diseases
-New, more successful competitors
-A single catastrophic event

45
Q

Why do humans use selective breeding?

A

To produce:
Disease resistance in food crops.
Animals which produce more meat or milk.
Domestic dogs with a gentle nature.
Large or unusual flowers.

46
Q

What are the steps for selective breeding?

A

1) Choose parents that best show the desired characteristics.
2) Breed them together.
3) From the offspring again choose those with the desired, characteristics and breed.
4) Continue over many generations.

47
Q

What type of characteristics are chosen for selective breeding?

A

-Disease resistance in food crops.
-Animals that produce more meat/milk.
-Large/unusual flowers.

48
Q

What can inbreeding lead to?

A

It can lead to inherited defects or being prone to disease.

49
Q

What is genetic engineering and what does it involve??

A

Genetic engineering is a more recent way of bringing about changes in organisms.
It involves changing the characteristics of an organism by introducing a gene from another organism.

50
Q

What happens in genetic engineering?

A

1) Enzymes are used to isolate the required gene.
2) This gene is inserted into a vector eg a bacterial plasmid or a virus.
3) The vector is used to insert the gene into the required cells.
If they’re put into the cells of animals/plants at the egg/embryo stage then all cells will get the new gene.

51
Q

What are crops that have had their genes genetically modified called?

A

Genetically modified (GM) crops.

52
Q

What are the issues around GM crops?

A

Ethical issues and the fact that we don’t know what the long-lasting effect is on humans.

53
Q

How did Carl Linnaeus classify things into (KPCOFGS)

A

Kingdom, Phylum, Class, Order, Family, Genus, and Species.

54
Q

How are organisms named?

A

By the binominal system. ie they have 2 parts to their lasting name. 1st-Genus. 2nd-Specices.

55
Q

Why were new models of classification proposed?

A

-Microscopes improved so scientists learned more about cells.
-biochemical process became better understood.

56
Q

What is the new domain system proposed by Carl Woese divided into?

A

3 domain system.
Arcaea (primitive bacteria,
living in extreme conditions).
-Bacteria (true bacteria).
-Eukaryota (inc protists, fungi, plants and animals).

57
Q

Why are evolutionary trees used?

A

They’re used by scientists to show how they think organisms are related.

58
Q

Who worked on the theory of speciation?

A

Alfred Russel Wallace.

59
Q

What is the theory of speciation?

A

1) Populations become physically isolated from each other eg by an ocean.
2) Genetic variation is present between the two populations.
3) Natural selection operates differently in the two populations.
4) The population become so different that successful interbreeding is no longer possible.

60
Q

In plants what can identical plants be produced from?

A

Cutting-This method is often used by farmers.
Tissue culture- This uses small groups of cells to grow new plants and is used commercially and to preserve rare plant species.

61
Q

How can clones be produced in animals?

A

By splitting apart cells from an embryo before they become specialised and then transplanting the identical embryos into host mothers.

62
Q

How are clones produced by using adult cells?

A

1) Remove the nucleus from an unfertilised egg cell.
2) Insert the nucleus from an adult body cell of the organism you want to clone into the empty egg cell.
3) Stimulate the egg cell to divide using an electric shock.
4) Allow the resulting embryo to develop into a ball of cells.
5) Insert an embryo into the womb of a surrogate female to continue its development.

63
Q

To reduce the rate of development of antibiotic-resistant strains:

A
  • doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections
  • patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains.
  • the agricultural use of antibiotics should be restricted.
    The development of new antibiotics is costly and slow. It is unlikely to keep up with the emergence of new resistant strains.

Biology (8 decks)

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