chapter 10 p4

Question 1

Standard deviation

Answer 1

The standard deviation is a measure of how spread out the data is.
The greater the standard deviation is, the greater the spread of the data. In terms of variation, a characteristic which has a high standard deviation has a large amount of variation.
When you calculate the standard deviation of data that display a normal distribution you will generally find that:

Question 2

Answer 2

Question 3

Answer 3

Question 4

Other statistical tests:

Answer 4

Several statistical tests can be used by scientists to determine the significance of data collected.
These tests can be used in a number of situations, for example when comparing variation within populations, or when comparing the effects of abiotic and biotic factors on organisms

Question 5

These tests can be used in a number of situations, for example when comparing variation within populations, or when comparing the effects of abiotic and biotic factors on organisms (Chapter 11, Biodiversity).
These include:

Answer 5

Student’s test - this is used to compare the means of data values of two populations
Spearman’s rank correlation coefficient - this is used to consider the relationship of between two sets of data.

Question 6

Student’s t test:

Answer 6

Student’s t test is used to compare the mean values of two sets of data.
To use this test the data collected must be normally distributed and enough data should be collected to calculate a reliable mean.
Different sample sizes may be used

Question 7

A significant difference at p = 0.05 means

Answer 7

that if the null hypothesis were correct (i.e., the samples or treatments do not differ) then we would expect to get at value as great as this on exactly 5% of occasions.
You can therefore be reasonably confident that the samples do differ from one another, but there is still nearly a 5% chance of this conclusion being wrong

Question 8

If the calculated t value exceeds the tabulated value for p = 0.01

Answer 8

then there is a 99% chance of the means being significantly different (and a 99.9% chance if the calculated t value exceeds the tabulated value for p = 0.001).

Question 9

By convention, a difference between means at the 95% level is

Answer 9

‘significant’, a difference at 99% level is ‘highly significant’ and a difference at the 99.9% level is ‘very highly significant’.

Question 10

Answer 10

Question 11

Spearman’s rank correlation coefficient:
If two sets of data are related they are said to be correlated. Iwo sets of data can show:

Answer 11

no correlation
positive correlation
negative correlation

Question 12

no correlation

Answer 12

no relationship between the data

Question 13

positive correlation

Answer 13

as one set of data increases in value, the other set of data also increases in value

Question 14

negative correlation

Answer 14

as one set of data increases in value, the other set of data decreases in value

Question 15

spearman’s rank formula

Answer 15

Question 16

Answer 16

Question 17

What are adaptations:

Answer 17

characteristics that increase an organism’s chance of survival and reproduction in its environment.

Question 18

Adaptations can be divided into three groups:

Answer 18

anatomical adaptations - physical features (internal and external)
behavioural adaptations - the way an organism acts. These can be inherited or learnt from their parents.
physiological adaptations - processes that take place inside an organism.

Many adaptations fall into more than one category.
For example, the courtship behaviour of a peacock requires it to lift its huge, colourful tail to attract the peahen.
This is an example of both a behavioural and anatomical adaptation.

Question 19

Anatomical adaptations:
Some examples of anatomical adaptations:

Answer 19

Body covering
Camouflage
Teeth
Mimicry

Question 20

Body covering

Answer 20

animals have a number of different body coverings such as hair, scales, spines, feathers, and shells.
These can: help the organism to fly, such as feathers on birds - help it to stay warm, such as the thick hair on polar bears - provide protection, such as a snail’s shell.
Thick waxy layers on plants prevent water loss and spikes can deter herbivores and protect the tissues from sun damage.

Question 21

Camouflage

Answer 21

the outer colour of an animal allows it to blend into its environment, making it harder for predators to spot it.
For example, the snowshoe hare is white in winter to match the snow, and turns brown in summer to blend in with the soil and rock environment in which it lives.

Question 22

Teeth

Answer 22

the shape and type of teeth present in an animal’s jaw are related to its diet.
Herbivores, such as sheep, have continuously growing molars for chewing tough grass and plants.
Carnivores, such as tigers, have sharp large canines to kill prey and tear meat.

Question 23

Mimicry

Answer 23

copying another animal’s appearance or sounds allows a harmless organism to fool predators into thinking it is poisonous or dangerous.
For example, the harmless hoverfly mimics the markings of a wasp to deter predators.

Question 24

Marram grass:

Answer 24

Marram grass (Ammophila spp.) is commonly found on sand dunes around the UK.
It is a xerophyte, a plant that has adapted to live in an environment with little water. Its adaptations reduce the rate of transpiration and include:
curled (or rolled) leaves to minimise the surface area of moist tissue exposed to the air, and protect the leaves from the wind
hairs on the inside surface of the leaves to trap moist air close to the leaf, reducing the diffusion gradient
stomata sunk into pits, which make them less likely to open and lose water
a thick waxy cuticle on the leaves and stems, reducing water loss through evaporation.

Question 25

Behavioural adaptations:
Some examples of behavioural adaptations:

Answer 25

Survival behaviours
Courtship
Seasonal behaviours

Question 26

Survival behaviours

Answer 26

for example, an opossum plays dead and a rabbit freezes when they think they have been seen.

Question 27

Courtship

Answer 27

many animals exhibit elaborate courtship behaviours to attract a mate. For example, scorpions perform a dance to attract a partner. This increases the organism’s chance of reproducing.

Question 28

Seasonal behaviours

Answer 28

these adaptations enable organisms to cope with changes in their environment.

They include:
- migration - animals move from one region to another, and then back again when environmental conditions are more favourable. This may be for a better climate or a source of food

hibernation - a period of inactivity in which an animal’s body temperature, heart rate and breathing rate slow down to conserve energy, reducing the animal’s requirement for food.
For example, brown bears hibernate during the winter.