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Biology > Inheritance, Variation and Evolution > Flashcards

Inheritance, Variation and Evolution Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are gametes?

A

Specialised cells for sexual reproduction.

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2
Q

What is the difference in cells produced by meiosis rather than by mitosis.

A

Cells produced by mitosis are genetically identical.

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3
Q

What are the gametes in flowering plants?

A

Pollen and egg cells.

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4
Q

What are gametes in animals?

A

Sperm and egg cells.

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5
Q

Why do pollen cells have a hard, protective coat?

A

To protect them from drying out in the air.

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6
Q

Why does sexual reproduction lead to a variety in the offspring?

A

Genetic information from the two parents is mixed together.

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7
Q

What happens in meiosis?

A

The genetic information is copied
The cell then divides twice
(Each of the four cells will now have half the normal number of chromosomes)

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8
Q

Where does meiosis take place?

A

In the reproductive organs of animals and plants.

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9
Q

How many chromosomes do humans have in each body cell?

A

46

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10
Q

Explain how fertilisation restores the normal number of chromosomes?

A

Humans have 46 chromosomes in each body cell
Meiosis halves the number of chromosomes in the gametes so sperm and egg cells have 23 chromosomes. When a sperm cell fuses with an egg cell, two single sets of 23 chromosomes are mixed together.

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11
Q

Why do the cells in an embryo differentiate?

A

The cells need to become specialised to carry out different functions.

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12
Q

What is the genome?

A

The entire genetic material of an organism

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13
Q

What is DNA?

A

A long polymer made of two strands twisted into a double helix.

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14
Q

What are chromosomes?

A

Long lengths of DNA are tightly coiled into structures.

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15
Q

What are genes?

A

Short sections of DNA that code for a specific protein.

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16
Q

What are the benefits of sequencing the human genome?

A
  • Knowing which genes are linked to specific diseases is helpful for treating people with inherited disorders
  • Mapping chromosomes allows the tracing of past human migration patterns
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17
Q

What does heterozygous mean?

A

Organisms with two different alleles of a gene.

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18
Q

What does homozygous mean?

A

Where the two alleles are the same.

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19
Q

What is a genotype?

A

The alleles an organism has.

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20
Q

What is a phenotype?

A

How the organism appears.

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21
Q

Why do human gametes only carry one allele of a gene?

A

Gametes are formed by meiosis which reduces 23 pairs of chromosome to just one of each pair.

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22
Q

What is the purpose of a punnet square?

A

To predict the genotypes and phenotypes for offspring produced by two parents.

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23
Q

Cystic fibrosis is caused by a … allele
Polydactyly is caused by a … allele

A

Recessive
Dominant

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24
Q

Why is the chance of two parents having a girl always 50%?

A

Egg cells contain an X chromosome so the sex of the child is decided by which sex chromosome is contained in the sperm cell, 50% of which contain an X chromosome.

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25
Q

What is the visible difference between an X and a Y chromosome?

A

The X chromosome is larger than the Y chromosome.

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26
Q

What is variation?

A

Differences in the characteristics of all those in a population.

27
Q

What are mutations?

A

Changes in genes. Most mutation have no effect in the phenotype of the individuals in the population.

28
Q

What is the difference in genetic variation and environmental variation?

A

Genetic variation occurs because of differences in the alleles inherited by individuals.
Environmental variation occurs if individuals develop in different conditions.

29
Q

What is natural selection?

A

When a mutation does alter a phenotype which might make it more suited to changing conditions. If this happens, these individuals will be more likely to survive and pass on the mutation to their offspring.

30
Q

When are two separate populations so different that they become two distinct species?

A

When they cannot interbreed to produce fertile offspring.

31
Q

Describe the process of evolution.

A

Evolution is a change in the inherited characteristics of a population over time due to natural selection which may lead to the formation of a new species.

32
Q

Explain the process of selective breeding.

A

Parents with the desired characteristics are carefully chosen and bred together to produce offspring. The offspring that show the desired characteristics are then selected and bred together. This process goes on fur many generations until all offspring have the desired characteristics.

33
Q

What is gene therapy?

A

Genes are inserted into some of a persons cells to reduce the symptoms of a genetic disorder.

34
Q

Why should genes be transferred to organisms at an early stage of their development.

A

So that the genetic modification can be transferred to more cells by mitosis during growth and so the GM organism has time to develop the desired characteristic.

35
Q

Describe the process of antibiotic resistance.

A

There are lots of bacteria, some have a resistant mutation.
Antibiotics kill all bacteria except those that have a mutation that gives them a resistance to the antibiotic.
The antibiotic-resistance bacteria are now able to grow and take over.

36
Q

Why do bacteria evolve rapidly?

A

Because they reproduce asexually they can reproduce at a very fast rate.

37
Q

Why is the fossil record evidence for natural selection?

A

Changes can be seen in the characteristics of a species over a long period of time.

38
Q

What are fossils?

A

Remains of organisms from millions of years ago.

39
Q

What are the three conditions that can cause the formation of fossils?

A
  1. Parts of animals/plants are prevented from decaying as one or more of the necessary conditions are absent
  2. Parts of the animal or plant are replaced by minerals as they decay
  3. Some fossils are the preserved traces of animals and plants
40
Q

Why is the fossil record incomplete?

A
  • animals or plants that died in water wouldn’t form fossils if they sank in mud or covered with sediment
  • animals or plants that died in land would have been likely to be eaten by scavengers
  • many fossils were destroyed by later geological activity
  • many of Earth’s earlier life forms were soft bodied and it is mainly the hard parts that form fossils
41
Q

What do evolutionary trees show?

A

How closely related species to one another.

42
Q

What is extinction?

A

When there are no individuals of a species remaining alive.

43
Q

What are some of the reasons for extinction?

A
  • the arrival of new predators in an area
  • the arrival of a new pathogen causing disease in an area
  • being outcompeted by another species for food
  • loss of habitat such as deforestation
  • a change in habitat such as a change in the climate due to global warming
  • a single large scale catastrophic event
44
Q

What does extinct in the wild mean?

A

When there are no wild individuals of the species left alive but there may be some in laboratories or botanic gardens.

45
Q

How can scientists increase the number of a species of tree to conserve the species?

A

Produce more individuals by using plant tissue culture.

46
Q

How should doctors reduce the rate of development of antibiotic resistant strains?

A
  • not prescribe antibiotics inappropriately such as for 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
47
Q

Why is it hard to keep up with the emergence of new resistant strains?

A

It is costly and slow to develop new antibiotics.

48
Q

Describe MRSA.

A

It is a strain of bacteria resistant to antibiotics.

49
Q

Why is it risky to give farm animals antibiotics to keep them productive?

A

There is a chance that a mutation providing antibiotic resistance could occur in bacteria in an animal being fed antibiotics and this resistant strain could then spread to humans and there would be no effective treatment.

50
Q

How did Carl Linnaeus classify organisms?

A

Based on their structure and characteristics.

51
Q

What is the order of Linnaeus’ system?

A

Kingdom phylum class order family genus species

52
Q

How have developments in biology affected the classification system?

A

Microscopes allow features of cells to be used and DNA similarities can now be used.

53
Q

What did Carl Woese develop?

A

The three domain system, based off chemical analysis, in this system organisms are now divided into:
Archaea
Bacteria
Eukaryota

54
Q

What are archaea, bacteria, and eukaryota?

A

Archaea: primitive bacteria usually living in extreme environments
Bacteria: true bacteria
Eukaryota: all other living things which includes protists, fungi, plants and animals

55
Q

What are three types of evidence that are used now to classify living things?

A

Chemical analysis
DNA
Studies of cell structures with electron microscopes

56
Q

Why is evolution easier to see in birds than in humans?

A

Shorter life cycle
More offspring
So the genetics of the population changes faster

57
Q

What evidence shows two individuals are of the same species?

A

Similar phenotype
Similar genotype
Produce fertile offspring if they breed together

58
Q

What is heterozygous?

A

Having two different alleles (recessive and dominant) for a gene

59
Q

How can two parents with no alleles for polydactyly produce a child with polydactyly?

A

A mutation during meiosis causing a change in amino acid sequence causing a different protein to be produced.

60
Q

Explain how long horns could have explored.

A

There would have been a variation in population and the animals with these longer horns would have been more likely to survive and reproduce. They would have passed on these alleles for long horns and this would have been repeated over generations.

61
Q

Explain why herbicide resistance leads to higher yields.

A

Wheat is not affected by spraying herbicides
So wheat gets more light, water and mineral ions so more photosynthesis can happen.

62
Q

What are examples of genetic engineering in use today?

A

Producing insulin
Disease resistance in crops

63
Q

How will the human genome project be useful in the future?

A

Identifying genes linked to certain genetic diseases so can lead to better treatment and prevention of that disease.

Biology (7 decks)

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