Topic 4

Question 1

How has variety of life changed over time?

Answer 1

Variety generally increases as new species form. However human activity is threatening much of the life on the planet

Question 2

What is meant by biodiversity?

Answer 2

The variety of living organisms. It can be measured in terms of number of species within a habitat, or by genetic variation within a species

Question 3

What is meant by endemism?

Answer 3

When a species found only in one geographical location, and is unable to be found anywhere else

Question 4

Define a niche

Answer 4

The role of a species within its habitat, consisting of both its biotic interaction.

Question 5

What are the three types of adaptation?

Answer 5

• Anatomical (changes to body structure) e.g. oily fur
• Physiological(changes to bodily processes) e.g. venom production
• Behavioural (changes to actions) e.g. hibernation

Question 6

Why does natural selection occur?

Answer 6

1. Predation
   2.Disease
   3.Competition
   All resulting in differential survival and reproduction

Question 7

Explain how natural selection results in adaptation and evolution

Answer 7

• Random mutations result in new alleles
• Some alleles provide an advantage, making an individual more likely to survive and reproduce
• Their offspring receive the new allele, and therefore possess new adaptations that allow them to survive in their environment; they have evolved

Question 8

What is the Hardy-Weinberg principle?

Answer 8

Allows us to estimate the frequency of alleles in a pollution, as well as if the allele frequency is changing over time

Question 9

Define speciation

Answer 9

Where a population is split and isolated, there are different selective pressures on the two groups

Question 10

Define classification

Answer 10

A means of sorting organisms into categories based on their relationships, using both genotypes and phenotypes

Question 11

How has research by the scientific community contributed to classification of organisms?

Answer 11

New data has led to new taxonomic groupings, the three domains; Bacteria, Archaea, and Eukaryota.

Question 12

Describe the structure and function of a plant’s cell wall

Answer 12

Made of cellulose. Outer layer is called the middle lamella. Holds adjacent cells together, as well as providing support and protection

Question 13

Describe the structure and function of a chloroplast

Answer 13

Contain thylakoid membranes which are stacked into grana. These contain chlorophyll. Surrounded by stroma, a liquid which contains photosynthetic enzymes

Question 14

Describe the structure and function of amyloplast

Answer 14

Produces and stored starch composed of amylose and amylopectin. Surrounded by a double membrane

Question 15

Describe the structure and function of the plasmodesmata

Answer 15

Extensions of the cytoplasm that connect two neighbouring cells together, allowing transport of substances between them

Question 16

Describe the structure and function of the pits

Answer 16

Thin sections of the cell wall that allow easy diffusion, therefore enabling substances to be transferred between cells

Question 17

Two examples of polysaccharides found in plants

Answer 17

• starch

- cellulose

Question 18

Relate the structure of starch to its function

Answer 18

Mixture of two polysaccharides;

• Amylose=coiled to make the molecule compact, so large amounts can be stored
• Amylopectin=highly branched, so energy can be released quickly