variation and selection (topic 18)

Question 1

variation

Answer 1

Differences between individuals of the same species

Question 2

genotypic variation

Answer 2

Differences between individuals of the same species due to differences in their genotypes

Question 3

phenotypic variation

Answer 3

Differences between individuals of the same species caused by both genetic factors and environmental factors.

Question 4

discontinuos variation

Answer 4

Differences between individuals of the same species in which there is a limited number of phenotypes with no intermediates.
cause by genes only

Question 5

continuos variation

Answer 5

Differences between individuals of the same species in which there is a range of phenotypes between two extremes.
caused by genes and enviornment

Question 6

give examples of discontinuos variation

Answer 6

ABO blood group
seed shapes and colour of peas

Question 7

give examples of continuoes variation

Answer 7

body length
body mass

Question 8

mutations

Answer 8

genetic changes
happen when there is a change in the DNA sequence of a cell
the way in which new alleles are formed
Mutations occur naturally through DNA replication errors but there are some factors that increase the rate of mutation

Question 9

what are some factors that increase the rate of mutation

Answer 9

ionising radiation such as gamma rays, X-rays and high energy ultraviolet electromagnetic waves.

some chemicals.

Question 10

gene mutation

Answer 10

a random change in the base sequence of DNA

Question 11

what are sources of genetic variation in populations

Answer 11

mutation, meiosis, random mating
and random fertilisation

Question 12

what is an adaptive feature

Answer 12

an inherited feature that helps an organism to survive and reproduce in its environment

Question 13

species

Answer 13

A group of similar organisms that can reproduce to produce fertile offspring.

Question 14

hydrophytes

Answer 14

An organism adapted to live in or on water.

Question 15

xerophytes

Answer 15

An organism adapted to live in dry, arid environments

Question 16

adaptations of hydrophytes

Answer 16

large thin leaves, stomate on upper surface
little or no waxy cuticle, water loss not a problem
long leaf stalks with large air spaces to help them float
reduced root system no need to be anchored to the ground
poorly developed xylem tissue, allows transport of water but provides little structure

Question 17

xerophytes adaptations

Answer 17

-thick waxy cuticle layer covering upper epidermis of leaves to reduce water loss
-few stomata, or stomata that are sunken into pits surrounded by hair to reduce water loss by transpiration
-curled, rolled or folded leaves, which reduce the surface area available for transpiration
-adaptations to store water, thick succulent stem, widley spread roots to absorb as much water, very deep roots to reach undrground water syste,

Question 18

describe the steps to natural selection

Answer 18

1- variation present in inherited characteristics shown by individual in a population
2- populations produce many offsprings more than can be supported by habitat
3-competition between individuals for resources
4-struggle for survival, indivudlas more likely to survive and reproduce
5-individuals better adapted to their enviornment are more likely to survive and reproduce
6-offsprings of better adapted individuals are more likely to inherit alleles, make them better adapted to their enviornment
7-steps repeat from one generation to the next, population changes

Question 19

outline 4 steps that causes natural selection

Answer 19

variation
over production
selection
adaptation

Question 20

describe adaptations

Answer 20

the process, resulting
from natural selection, by which populations
become more suited to their environment over many generations

Question 21

describe antibiotic resistence

Answer 21

mutations may occur in the bacteria, while it reproduces very quickly, this allows them to become resistant to antibiotics
if bacteria treated with antibiotics, those that are mutated will survive while those that arent wont
the ones that survive will reproduce and pass their alleles and genes resistant to the antibiotic to their offsprings
soon whole population is resistant to the antibiotic

Question 22

selective breeding

Answer 22

The process by which animals or plants are bred to produce offspring with particular, desirable, characteristics.

Question 23

describe process of selective breeding

Answer 23

selection by humans of individuals with
desirable features
crossing these individuals to produce the
next generation
selection of offspring showing the desirable
features

Question 24

why is selective breeding used

Answer 24

improve crops, and domestic animals over many generations

Question 25

differences in artificial and natural selection

Answer 25

natural selection- driven by naturally occurring processes, variation makes most adapted organisms to survive and reproduce

artificial selection- selection imposed by humans, depends on the breeder, less variation breeder must be careful for organisms not to become so susceptible to diseases or changes in environment, has disadvantages such as inbreeding, parents may carry undesirable traits which can be passed on to offsprings

Question 26

how can you make sure a plant is homozygous

Answer 26

produce a test cross