Ecological Pyramids

Question 2

What are ecological pyramids?

Answer 2

Graphical models of the quantative differences between amounts of living material stored at each trophic level of a food chain.

Question 3

What does a pyramid of numbers show?

Answer 3

The numbers of organisms at each trophic level in a food chain at one time. Also known as the standing crop.

Question 4

What are the units for pyramid of numbers?

Answer 4

number per unit area

Question 5

Advantage of pyramids of numbers?

Answer 5

Simple, easy method of giving an overview and is good at comparing changes with time.

Question 6

Disadvantages of pyramids of numbers?

Answer 6

All organisms are included regardless of size, so they can be inverted with a large primary producer such as an oak tree. Does not allow for juveniles. Numbers can be too great to represent accurately.

Question 7

What does a pyramid of biomass show?

Answer 7

It contains the biomass at each trophic level.

Question 8

What is biomass?

Answer 8

The quantity of dry organic material in an organism/population.

Question 9

How do you calculate the biomass at each trophic level in a pyramid of biomass?

Answer 9

The biomass of each individual times by the number of individuals.

Question 10

What are the units for a pyramid of biomass?

Answer 10

mass per unit area

Question 11

What are the advantages of a pyramid of biomass?

Answer 11

overcomes some of the problems of pyramids of numbers

Question 12

What are the disadvantages of a pyramid of biomass?

Answer 12

Organisms must be killed to measure Only uses samples from populations so not entirely accurate Time of year can have an affect on biomass

Question 13

What does a pyramid of productivity show?

Answer 13

The rate of flow of energy or biomass through each trophic level.

Question 14

How are pyramids of productivity different to those of biomass or numbers?

Answer 14

They show the flow of energy over time where as the others are during a fixed period of time.

Question 15

What are pyramids of productivity measured in?

Answer 15

Energy or mass per unit area per period of time. e.g. J m-2 yr-1

Question 16

Advantages of a pyramid of productivity?

Answer 16

Most accurate system, shows actual energy transferred Allows comparison of ecosystems based on relative energy flow Always pyramid shaped, never inverted Energy from solar radiation can be included

Question 17

Disadvantages of a pyramid of productivity?

Answer 17

Very complex data collection process Hard to assign a species to just one trophic level when they might be omnivores

Question 18

Describe the process of bioaccumulation:

Answer 18

If a chemical that breaks down slowly is ingested or inhaled by an organism and they do not excrete or egest it, it accumulates in their bodies over time. If the chemical stays in the ecosystem for a prolonged period of time, the concentration builds up. Eventually this can cause disease or death.

Question 19

Describe the process of biomagnification:

Answer 19

If an organism eats a plant that has a chemical in its tissues, the concentration in that organism is higher than the plant as it eats multiple plants over time. In this way the concentration of the chemical is increased at each trophic level. At top trophic levels the concentration could be enough to cause disease.

Question 20

What animals did DDT have an effect on?

Answer 20

peregrine falcons as it weakens their egg shells

Question 21

What is the trophic efficiency?

Answer 21

In general 10% but can range from 5-20