Energy and ecosystems

Question 1

Define net primary productivity

Answer 1

Total chemical energy available for plant growth, plant reproduction and energy transfer to other trophic levels after respiratory losses.

Question 2

Define gross primary production.

Answer 2

Total chemical energy in plant biomass within a given volume or area.

Question 3

What is the relationship between GPP and NPP?

Answer 3

NPP = GPP - R
where R is the respiratory losses from plants

Question 4

What is biomass?

Answer 4

Total dry mass of tissue or mass of carbon measured over a given time in a specific area.

Question 5

What is the unit for biomass?

Answer 5

Area gm^-2
Volume gm^-3

Question 6

Why does biomass decrease at each trophic level?

Answer 6

• energy is lost in nitrogenous waste (faeces/ urine)
• Some of the organism is not consumed
• Energy lost to surroundings as heat

Question 7

What is the equation for % efficiency?

Answer 7

(energy converted to a useful form (J)) x 100 / total energy supplied (J)

Question 8

State what is meant by the term ecosystem.

Answer 8

organisms and abiotic/ non - living factors

Question 9

Define community

Answer 9

All the different species that live in one area and interact with each other.

Question 10

How do niches affect the abundance and distribution of organisms in a habitat?

Answer 10

No two species can occupy the same niche; interspecific competition excludes one species or the niche is divided according to its adaptations.

Question 11

What is meant by primary succession?

Answer 11

When an area previously devoid of life is colonised by a community of organisms.

Question 12

Summarise the process of primary succession

Answer 12

• pioneer species can survive harsh conditions and colonise the area.
• They change abiotic factors of their environment e.g decomposition adds nutrients to the ground
• Over time, more complex organisms survive and outcompete the initial species.

Question 13

What is a climax community?

Answer 13

Final seral stage of succession. Ecosystme is stable in dynamic equilibrium over a long period of time. Usually dominated by large trees or shrubs in rich soil.

Question 14

What is evolution?

Answer 14

Change in allele frequency in gene pool of a population. Results in development of new dominant characteristics.

Question 15

How does natural selection lead to evolution?

Answer 15

• Random mutations result in new alleles
• Some alleles provide an advantage, making an individual more likely to survive and reproduce.
• Offspring recieve the new allele and frequency increases over many generations. Frequency of unfavourable alelles decreases.

Question 16

Define speciation

Answer 16

When a population is split and reproductively isolated, there are different selective pressures on the two groups. If the genetic makeup changes to the extent the two groups can no longer interbreed, they have become separate species.

Question 17

What is meant by allopatric speciation?

Answer 17

Speciation resulting from a physical barrier e.g river, mountain range. The environments occupied by the two groups are different, and therefore different alleles are favoured.

Question 18

What is meant by sympatric speciation?

Answer 18

Speciation resulting from a non -physical barrier e.g mutation that no longer allows two organisms to produce fertile offspring. Any changes in anatomy or behaviour may also prevent breeding.

Question 19

How can we analyse evolutionary relationships on a molecular level?

Answer 19

Genomics: gel electrophoresis, DNA sequencing, bioinformatics.
Proteomics: analysis of amino acid sequence.

Question 20

How do proteomics and genomics support the theory of evolution?

Answer 20

Universal code. Species with fewer differences in base sequence have more homologous characteristics. Suggests diversion form common ancestors.