B14 - Variation and Evolution

Question 1

What is variation

Answer 1

Differences in the characteristics of individuals in a population

Question 2

What two things contribute to variation?

Answer 2

• Genetics (Nature)
• Environment (Nurture)

Variation can be caused by a combination of these factors

Question 3

Examples of variation caused by genetics

Answer 3

• Eye colour
• Gender
• Blood type

Question 4

Examples of variation caused by environment

Answer 4

• Scarring
• Language
• Muscle strength

Question 5

How does a mutation cause variation

Answer 5

• Mutations are uncontrollable, constantly occuring changes in DNA
• This may lead to a new phenotype
• This may give an organism desired characteristics making it better suited to an environment

Question 6

What is evolution

Answer 6

Changes in the inherited characteristics in a population over time through the process of natural selection

Question 7

Outline the stages in the theory of evolution by natural selection (5 steps)

Answer 7

• Mutations which cause variation
• Survival - better adapted to environment
• Reproduction
• Pass on beneficial alleles
• More offspring with allelle (alleic frequency increases)

Question 8

What is selective breeding

Answer 8

Where humans breed animals or plants in order to get offspring with certain desired characteristics

Question 9

Describe the main steps in the process of selective breeding

Answer 9

• Find parents with desired characteristics in population and breed them
• Breed the offspring with the best characteristics
• Continue for many generations until all have desried characteristics

Question 10

Examples of characteristics that could be selected in selective breeding

Answer 10

• Animals that produce lots of milk or meat
• Domestic dogs
• Disease resistant plants
• Types of flowers

Question 11

Problems with selective breeding

Answer 11

• Lack of variation - leaves organisms vunerable to changes in environment
• Can unknowingly spread genetic defect

Question 12

What is genetic engineering

Answer 12

Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

Question 13

Describe the process of genetic engineering

Answer 13

• Enzymes isolate the required gene
• The gene is the put into a bacterial plasmid which acts as a vector
• The vector inserts the genes into the required cells
• The genes are insterted in early development allowing the organism to develop with desired characteristics

Question 14

Uses of genetic engineering

Answer 14

• Bacterial cells to produce insulin
• Plants + GM Crops - bigger, increased yield, resistant to diseases

Question 15

Benefits of genetic engineering

Answer 15

• Increased crop yield
• Faster results compared to selective breeding
• Herbicide/insect/drought resistance
• Increased nutritional value

Question 16

Problems/risks with genetic engineering

Answer 16

• Gene could get into other species or environment causing herbicide resistant weeds
• Some people see it as “playing God”
• Unknown effects on humans

Question 17

2 methods of cloning plants

Answer 17

• Taking cuttings
• Tissue culture

Question 18

Describe the method of cloning plants by using cuttings

Answer 18

• Old, simple method used by gardeners
• Branch from parent taken
• Placed in damp compost with nutrients and hormones

Question 19

Describe the method of cloning plants by tissue culture

Answer 19

• USed to preserve rare plant species
• Explants are placed in agar that contains nutrients and hormones
• Platelets grow
• They are then placed in compost

Question 20

Describe the process of animal cloning by embryo transplants

Using cows for example

Answer 20

• Cow given fertitlity drugs and artificially inseminated with sperm from a bull
• Zygotes develop into embryos and then taken from cow
• Embryos are split into smaller embryos
• All embryos are genetically identical and are placed in surrogate mothers

Question 21

Describe the process of adult cell cloning

Answer 21

• Nucleus removed from egg cell
• Nucleus from adult cell e.g. skin cell placed in egg
• Egg is then shocked to start cell division
• Embryo has same genetic info as nucleus from skin cell
• Once embryo has developed, it is placed in a surrogate mother

Question 22

Benefits of adult cell cloning

Answer 22

• Save animals from extinction
• Bring back animals that are already extinct

Question 23

Drawbacks of adult cell cloning

Answer 23

• Could lead to human cloning which is illegal
• Reduces variation making a species vunerable to environment changes
• Designer babies