B4 - Community Level Systems

Question 1

What is sampling?

Answer 1

estimating the amount of organism in an ecosystem by looking at a smaller area

Question 2

Why is it hard to sample?

Answer 2

• Some things are very small - such as bacteria
• Many organism avoid humans - hard to detect
• Many organisms look very similar and difficult to determine what species they are

Question 3

Sampling methods for stationary or slow moving organisms - like plants?

Answer 3

Quadrats : A 1m by 1m square used to estimate organisms present in an ecosystem with the same abiotic factors throughout

Line transects : a line (rope or tape) laid through an ecosystem to sample organisms and observe change in organisms due to change in abiotic factors

Belt transects: a line (rope or tape) laid through an ecosystem with quadrats place along it to sample organisms and observe change in organisms due to change in abiotic factors

Question 4

Sampling methods for mobile organisms - like animals?

Answer 4

Capture methods:
1) Pit fall trap: There is a pit concealed to be undetected by insects. The insect fall into it when stepped on
2) Pooter: Person sucks on straw which
will suck up any insects to be collected
3) Net: used for aquatic and flying organism to collect

Question 5

Why is the pooter method not a random sampling method?

Answer 5

Pooter: will disproportionately capture more visible and slower insects and will not give reliable data

Question 6

What is the capture-recapture method?

Answer 6

• It estimates population size of animals
  1) Capture the animals - using capture method (pitfall trap, pooter or nets) and mark the animals in a harmless way to their survival before releasing them again

2) After a few days capture the animals again

3) Use formula:
(Number of animals in 1st capture X Number of animals in 2nd capture) / Number of Marked animals in 2nd capture

Question 7

Why might marking the organisms in capture-recapture method limit the experiment?

Answer 7

• May make animals more visible and less camouflage to predators
• May come undone or washed off and results unreliable
• Toxic chemicals may be dangerous

Question 8

What is zonation?

Answer 8

The gradual change of a community of organism over a certain distance due to change in abiotic factors (an example is a beach - ocean, to tidal area, to beach, to forest have different organism occupying it)

Question 9

Population, ecosystem, habitat, individual, community definitions?

Answer 9

Individual: A single organism

Population: All the organisms of one species in a habitat

Community: All the organisms - of different species - living in a habitat

Ecosystem: A community of organisms along with all the nonliving factors (abiotic) conditions

Habitat: where an organism lives

Question 10

The carbon cycle:

Answer 10

1) Co2 in the air is absorbed by plants for photosynthesis
2) Some carbon is recycled to the air when plants respire
3) Carbon absorbed by plants is transferred to animals when they are consumed - the carbon atoms rearrange into the animal’s carbohydrates, fats or proteins
4) Animal respires
5) When the plant or animal die they are broken down by bacteria which require while doing so - releases carbon dioxide into atmosphere
6) The dead material could also be turned into fossil fuels which return CO2 into the environment when they are combusted

Question 11

What is decomposition and why is it important?

Answer 11

Decay is when dead materials are broken down into simpler chemicals by microorganisms

It is important to return nutrients to the soil so new plants can grow.

Question 12

Factors affecting rate of decomposition?

Answer 12

TEMPERATURE:
-Warm temperatures decay is fastest:
In hot conditions decomposition is slow as enzymes for decay denature
-In cold conditions decay is slow as there is no energy to respire for decomposition

OXYGEN:

• Bacteria cells need to respire to release energy
• If there is no oxygen bacteria cannot respire ,except anaerobically which releases less energy (this is why we package food)

WATER:
-Enzymes usually work in liquid solutions - like the cytoplasm - and if the bacteria release enzymes for extracellular digestion and there is lack of water the enzyme doesn’t work

Question 13

What is the type of relationships in an ecosystem?

Answer 13

Mutualism: both organism benefit

Commensalism: where one organism benefits and the other one isn’t affected either way

Parasitism: one organism benefits and the other is harmed

Question 14

What is competition and what are the types?

Answer 14

• Where two organisms are in competition for something they need

Plant (light, space, nutrients)

Animal (food, habitat, mates)
Intraspecific: competition within a species
Interspecific: competition between species

Question 15

What is abiotic and biotic factors and some examples?

Answer 15

ABIOTIC: non living

• Moisture levels
• pH levels
• carbon dioxide levels
• temperature
• Light intensity

BIOTIC: living

• New predators
• New pathogens
• Competition between species
• Food availability

Question 16

What is a kite diagram?

Answer 16

• It graphically shows the results of a transect

- The thickness of each kite is the amount of organisms present at that specific distance

Question 17

What is the predator prey cycle?

Answer 17

1) Normal prey population
2) Prey population increases
3) Predator population increase as more food
4) Prey population decrease because more predators
5) Predator population decrease as there is less food
6) prey population increase
CYCLE RESTART

There are always less predators than prey in an ecosystem due to idea of energy lost at each trophic level - prey have more energy to reproduce and have more offspring

Question 18

What does the arrows on a food chain/ web show?

Answer 18

The direction of energy transfer

Question 19

What is biomass?

Answer 19

The scientific term for plant and animal material not considering water weight

Question 20

What is a pyramid of biomass?

Answer 20

• Each bar shows the biomass of the living material in each stage of the food chain
• Its a pyramid shape - the producers are the largest bar and it gradually get smaller- as energy is lost between each stage

Question 21

What is a pyramid of numbers?

Answer 21

• Each bar shows the number of organisms at each stage of the food chain - not mass
• these don’t have to be a pyramid shape

Question 22

Why is the never beyond 4 trophic levels:

Answer 22

• Every trophic level, energy is lost for a variety of reasons, therefore at the top of the food chain there is always less energy than the producers
• There would not be enough energy to sustain an organism higher than 4 trophic levels

Question 23

How is biomass lost between each stage?

Answer 23

• Green plant use energy from the sun to make their own biomass, the rest is lost through plant respiration
• When energy is transferred to animals biomass is lost through respiration - for movement, keeping warm etc.
• Biomass lost through egestion and excretion
  egestion: is getting rid of undigested food - eg animal faeces
  excretion: is getting rid of waste products from chemical reactions in body - eg sweating, urinating and breathing out

Question 24

How to calculate efficiency of biomass transfer?

Answer 24

efficiency = (biomass available to next level / biomass that was available to previous level) x 100

Efficiency of biomass transfer = (Energy used to make biomass / energy intake) x 100

Question 25

Assumptions made in the capture recapture method?

Answer 25

• Marks may make animals more visible and less camouflage to predators
• Marks may come undone or washed off and results unreliable
• Marks may be toxic chemicals may be dangerous
• There is no migration of organism
• There is no deaths or births of organism