14: Ecosystems

Question 1

Define:
- Community
- Population
- Ecosystem
- Niche

Answer 1

1. all the organisms in a habitat
2. all the individuals of one species in a habitat
3. consists of the community and the abiotic components of the ecosystem
4. an organisms role in its ecosystem

Question 2

What is the ecosystem made up of?

Answer 2

• abiotic factors (physical + chemical)
• biotic factors (due to interactions of organisms in an area

Question 3

Name 5 abiotic + biotic factors:

Answer 3

Abiotic:
- light intensity
- climate
- wind speed
- rainfall
- CO2 levels
Biotic:
- predation
- food availability
- parasitism
- disease
- competition

Question 4

What are the 2 types of Competition?
Define them:

Answer 4

1. intraspecific competition: occurs between individuals of the same species for the same resource
2. interspecific competition: between different species

Question 5

Why can’t 2 species occupy the same niche?
What is the correlation between niche and competition?

Answer 5

1. • there would be too much interspecific competition between them for the same resources
   • this could lead to animal death, or even such competition that species disappear from area due to competitive exclusion
2. • the more similar the niche, the greater the competition

Question 6

Give 3 examples of Intraspecific competition in Plants:

Answer 6

• light
• water
• minerals

Question 7

Describe the correlation between prey and predators:

What effect will this decline in prey numbers have on predators?

What is the overall effect?

Answer 7

1. as the number of predators increase, the prey population declines
2. • the decreased food leads to more intraspecific competition => less reproduction => increased mortality => decreased predator population
   • therefore, more prey will survive and reproduce to increase population
3. • the overall effect is that both populations will fluctuate, but only within narrow limits, as each species is preventing the other from increasing beyond the number that the environment will support
   • the changes in predator population “lags behind the changes in prey population

Question 8

Define the ‘Carrying Capacity’:

What factors affect ‘Carrying Capacity’?

Answer 8

1. the maximum size that a population can remain sustainable in a particular habitat
2. • effect of abiotic factors e.g rainfall
   • intraspecific competition for food and resources

Question 9

Define:
- autotrophs
- heterotrophs
- trophic level

Answer 9

1. primary producers e.g green plants + algae
2. primary/secondary/tertiary consumers
3. each of these feeding roles

Question 10

A food chain usually has 4/5 trophic levels but rarely 6, why so?

Answer 10

• energy is releases to the environment at each trophic level, therefore there is not enough energy at the end of the food chain to support further trophic levels

Question 11

What are saprobionts?
Are they in a trophic level?

Answer 11

• these are organisms that digest dead remains and waste products (detritus) of every type of organism, releasing inorganic molecules and ions
• no

Question 12

What is the ultimate source of energy?
Why does not all light energy that falls on a plant used for photosynthesis?

Answer 12

1. Sun
   - some of the light does not fall on the photosynthetic parts of the plant, e.g not striking chlorophyll
   - some of the light is not of an appropiate wavelength, to be used in photsynthesis
   - some of the light is reflected or transmitted directly through the leaf

Question 13

Of the Light Energy that could be used for photosynthesis, only a small amount can be used for photosynthesis, why so?

Answer 13

• energy is lost during inefficient reactions of photosynthesis, or there may be other limiting factors e.g CO2 concentration

Question 14

What percent of solar energy is converted into biomass?
What is the biomass used for?

Answer 14

• overall 5% or less is converted into new biomass e.g glucose from photosynthesis
• used mainly for aerobic respiration, and the rest is used to make other biological molecules

Question 15

What is Biomass?

How would you estimate Biomass of a field of crops?

Why dry the crops at regular intervals?

Answer 15

1. mass of organic material in an organism/ecosystem
2. • collect all crops in one square metre, including roots
   • weigh initial mass, dry at 80 Degrees Celsius, weigh them and dry again, repeating until there is no further mass change
   • this means all water has been removed
   • Multiply mass by the number of square metres in the field
3. amount of water in any living organism varies over time

Question 16

In Calorimetry:
- how is the change in energy measured?
- what is the function of the stirrer?
- how can the calorimeter be modified to reduce heat loss to environment?

Answer 16

1. • dry material is burnt in oxygen
   • energy given off heats up the water in the calorimetry
   • rise in temperature can be used to calculate the energy in the material
2. distributed heat evenly in water
3. cover in insulating material (e.g bubblewrap)

Question 17

What is the Net Primary Production Formula?
What is Net Primary Production?
What is Gross Primary Production?

Answer 17

NPP = Gross Primary Production (GPP) - Respiration
NPP = chemical energy store in plant biomass after respiratory losses to the environment have been taken into account
GPP = chemical energy store in plant biomass, in a given area or volume

Question 18

Why are there energy loss between consumers?
What happens to these decomposed energy losses?

Answer 18

1. • some of the food taken in is not digested, (e.g lost in faeces)
   • some is lost due to excretion of metabolic waste products (urea)
   • some energy remains in parts of organisms that are not consumed, e.g bones/teeth
2. decomposed by saprobionts

Question 19

How is most energy lost?

Answer 19

• respiration => all energy transferred to environment as heat

Question 20

Net Production formula:

Answer 20

N = I - (F+R)
I = chemical energy stored in ingested food
F = energy lost to environment in faeces
R = energy lost due to respiratory losses

Question 21

Describe 2 ways efficiency of energy transfer can improve in Farming Practices:

Answer 21

• reducing respiratory losses within a human food chain
• simplifying food webs to reduce energy losses to non- human food chains e.g the use of pesticides to prevent crops being eaten by pests

Question 22

What is Succession?

Answer 22

• the way in which the different species of organisms make up a community change over a period of time

Question 23

Describe the writing frame for Succession:

Answer 23

1. hostile environment - colonised by pioneer species
2. abiotic environment of habitat changed by pioneer species
3. changed environment becomes more suitable to support new species
4. establishment of new plant species increases the species diversity as various groups of animals enter the habitat; the early colonisers are replaced by the new species
5. changes in abiotic factors result in a less hostile environment and increase in biodiversity
6. climax community develops

Question 24

What is primary succession?
What is secondary succession?

Answer 24

1. takes place on bare rock/sand, on which no community has previously been established
2. takes place in an area that has been previously colonised, but has been disturbed (e.g a forest fire)