T6 variation and evolution Flashcards Preview

aqa gcse biology free > T6 variation and evolution > Flashcards

Flashcards in T6 variation and evolution Deck (36)
Loading flashcards...
1
Q

what is variation

A

differences in the characteristics of individuals in a population

2
Q

what are the causes of variation within a species

A

genetics

environment

3
Q

what is genetic variation

A

variations in the genotypes of organisms of the same species due to the presence of different alleles

creates differences in phenotypes

4
Q

what creates genetic variation in a species

A

spontaneous mutations

sexual reproduction

5
Q

3 types of gene mutation

A

insertion

deletion

substitution

6
Q

how may a gene mutation affect an organisms phenotype

A

neutral mutation doesn’t change the sequence of amino acids, protein structure and function same, no effect

mutation may cause minor change in phenotype

may completely change the sequence of amino acids, resulting in a non-functional protein, severe changes to phenotype

7
Q

consequence of a new phenotype caused by a mutation being suited to an environmental change

A

rapid change in the species

8
Q

what is evolution

A

gradual change in the inherited trains within a population over time

occurs due to natural selection which may result in the formation of a new species

9
Q

outline the theory of natural selection

A

all species of living things have evolved from simple life forms that first developed more than 3 billion years ago

  1. genetic variation exists due to spontaneous mutations
  2. selection pressures exist
  3. random mutation gives an organism a selective advantage
  4. organism is better adapted to the environment and survives
  5. organism reproduces, passing on its beneficial alleles
  6. frequency of advantageous alleles increases
10
Q

how do two populations become different species

A

when their phenotypes become different to the extent that they no longer interbreed to produce fertile offspring

11
Q

outline main steps in selective breeding

A
  1. identify desired characteristic
  2. select parent organisms that show the desired traits and breed them together
  3. select offspring with desired traits and breed them together
  4. process repeated until all offspring have the desired traits
12
Q

examples of characteristics selected for in selective breeding

A

disease resistance in crops

higher milk or meat production in animals

large flowers

13
Q

advantages of selective breeding

A

creates organisms with desirable features

14
Q

where is selective breeding useful

A

medical research

sport eg horse racing

agriculture

15
Q

outline the disadvantages of selective breeding

A

reduction in the gene pool (becomes harmful is sudden environmental change occurs)

inbreeding results in genetic disorders

development of physical problems

potential to unknowingly select harmful recessive alleles

16
Q

what is genetic engineering

A

modification of the genome of an organism by the insertion of a desired gene from another organism - genes from chromosomes of humans and other organisms can be cut out and transferred to cells other organisms

enables the formation of an organism with beneficial characteristics

17
Q

what is a use for genetically modified bacteria cells

A

produce human insulin to treat diabetes mellitus

18
Q

describe the effects of genetic engineering

A

increased crop yields for growing population

useful in medicine possibly to overcome some inherited disorders

GM crops produce scarce resources (golden rice produces beta-carotene (source of VA in body))

19
Q

risks of genetic engineering

A

long-term effects of consumption of GM crops unknown

negative environmental impacts

late-onset health problems in GM animals

GM seeds are expensive, LEDC may be unable to afford or may become dependent on businesses that sell them

20
Q

what is bacillus thuringiensis (Bt)

A

insect larvae are harmful to crops

bacterium which secretes a toxin that kills insect larvae

21
Q

how is genetic engineering used to protect crops against insects

A

gene for toxin production in Bt can be isolated and inserted into the DNA of crops

Bt crops now secrete toxin which kills any insect larvae that feed on it

22
Q

benefits of Bt crops

A

increased crop yields

lessens need for artificial insecticides

Bt toxin is specific to certain insect larvae so is not harmful to other organisms that ingest it

23
Q

risks of Bt crops

A

long term effects of consumption unknown

insect larvae may become resistant to toxin

killing reduces biodiversity

24
Q

describe the process of genetic engineering

A
  1. DNA is cut at specific base sequences by restriction enzymes to create sticky ends
  2. vector DNA cut using the same restriction enzymes to create complementary sticky ends
  3. ligase enzymes join the sticky ends of the DNA and vector DNA forming recombinant DNA
  4. recombinant DNA mixed with and taken up by target cells
25
Q

what is a vector

A

structure that delivers the desired gene into the recipient cell

26
Q

how can plants be cloned

A

taking plant cuttings

tissue culture

27
Q

what is tissue culture

A

using small groups of cells from part of a plant to grow identical new plants

28
Q

describe how plants are grown using tissue culture

A
  1. select a plant showing desired characteristics
  2. cut multiple small sample pieces from meristem tissue
  3. grow in a petri dish containing growth medium
  4. transfer to compost for further growth
29
Q

what must be ensured when preparing tissue culutres

A

aseptic conditions to prevent contamination by microorganisms

30
Q

what does the growth medium contain

A

nutrients and growth hormones

31
Q

advantages of growing plants by tissue culture

A

fast and simple process

requires little space

enables growth of many plant clones with same desired characteristics

useful in preservation of endangered plant species

32
Q

disadvantages of growing plants by tissue culture

A

reduction in gene pool

plant clones often have a low survival rate

could unknowingly increase the presence of harmful recessive alleles

33
Q

brief overview of plant cuttings method of plant cloning

A

older but simpler method than tissue culture

gardeners use this method to produce many identical new plants from a parent plant

34
Q

detail the process of plant cuttings method of plant cloning

A
  1. branch is cut off from the parent plant
  2. lower leaves of the branch are removed and the stem is planted
  3. plant hormones are used to encourage new root development
  4. plastic bag covers the new plant to keep it warm and moist
  5. new roots and a new plant is formed after a few weeks
35
Q

what does embryo transplanting involve

A

pre-specialised cells from a developing animal embryo are spilt apart

resulting separate but identical embryos are transplanted into host mothers

36
Q

describe how adult cell cloning is performed

A
  1. nucleus removed from unfertilised egg cell
  2. nucleus from adult body cell is inserted
    into the egg cell
  3. electric shock stimulates the nucleated egg to divide and it forms an embryo
  4. embryo cells contain the same genetic information as the adult body cell
  5. when the embryo is a ball of cells, inserted into the uterus to continue developing