4. Communities and Ecosystems Flashcards Preview

IB Biology SL > 4. Communities and Ecosystems > Flashcards

Flashcards in 4. Communities and Ecosystems Deck (20):

Do populations live in isolation?

no - they live together with other populations in ecological communities


Define 'community'.

a group of populations of different species living together and interacting with each other in an area.


There are many types of interaction between populations in a community. Name one important relationship.

trophic relationships - where one population of organisms feeds on another population


What is the complex network of feeding relationships in a community called?

a food web

If asked to describe what a food web is: "it shows how food chains are linked together into more complex feeding relationships within a community"


What do communities of living organisms interact with?

their environment (duh)
- soil, water and air around them


What is a communities 'abiotic environment'?

the non-living surroundings


How does a community form an 'ecosystem'?

by the communities interactions with the abiotic environment


Name one important interaction between community and abiotic environment?

I could equally have said: 'Name one important interaction in an ecosystem?'

important interaction: transfer of chemical elements because these are an essential part of nutrient recycling


Do ecosystems have the potential to be sustainable over long periods of time?



"If .... , ecosystems only require .... to continue indefinitely". Fill in the blanks.

1 - nutrients are recycled
2 - a supply of energy, usually light,


What experiment could you set up to show that "ecosystems only require a supply of energy and nutrients being recycled to continue indefinitely"?

a mesocosm - a small experimental area set up in an ecological research programme


Draw a diagram of a mesocosm. (p55)

- 5 litre clear glass jar
- seal to prevent entry or exit of all chemical substances
- air containing oxygen and carbon dioxide
- mud from bed of pond
- pond water containing autotrophs, consumers, detritivores and saprotrophs


Explain why autotrophs are in the mesocosm experiment. (p55)*

*This question may assume some knowledge about the mesocosm on page 55.

they are essential:
- produce carbon compounds
- regenerate oxygen use in cell respiration by other organisms in the mesocosm


Explain why saprotrophs are in the mesocosm experiment. (p55)*

*This question may assume some knowledge about the mesocosm on page 55.

they are essential:
- decompose dead organic matter
- recycle nutrients


Explain why consumers and detritivores are in the mesocosm experiment. (p55)*

*This question may assume some knowledge about the mesocosm on page 55.

may not be essential:
- normal part of ecosystems so they are included
- unethical to include large animals in mesocosms that cannot obtain enough food or oxygen


What is a quadrat?

a square sample area used in ecological research


How do you carry out quadrat sampling?

- locate an area and mark out gridlines along two edges of the area
- use random number generator to get two random numbers to use as coordinates
- place quadrat on ground with its corner at these coordinates
- record presence/absence of each species of interest inside the quadrat, or record number of individuals
- repeat with as many quadrats as possible


What signals that you should do a chi-squared test?

if the presence or absence of two species is recorded in a large number of quadrats


What does the 'chi-squared test' test?

in ecology it tests the association between two species


Know how to do a chi-squared test. Dunno if you might be asked to do it in the exam.


Decks in IB Biology SL Class (85):