Summarised Notes on Module 4 – Ecosystem Dynamics

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Module 4 Summary – Ecosystem Dynamics

Inquiry Question 1: What effect can one species have on the other species in a community?

• Investigate and determine relationships between biotic and abiotic factors in an ecosystem including: 
  • The impact of abiotic factors,  
  • The impact of biotic factors, 
  •  including predation, competition and symbiotic relationships
  • The ecological niches occupied by species
  • Predicting consequences for populations in ecosystems due to predation, competition, symbiosis and disease. 
  • Measuring populations of organisms using sampling techniques.

Impact of abiotic factors:

Factors: Effect:
-Temperature – Types of organisms
– Oxygen Availability – Abundance (plants and animals)
– Water Availability – Distribution (plants and animals)
– Light intensity – Food availability
– Buoyancy  – Competition
– Pressure – Niches
– Communities 

Impact of biotic factors including predation, competition and symbiotic relationships:

Biotic factors: Effect:
– Availability of food – Abundance (plants and animals)
– Competition for territory – Distribution (plants and animals)
– Number of predators – Population structure of organisms.
– Ability to find a mate
– Disease + parasites 

Predation increases chance of survival or the predator at the expense of the prey and leads to → fluctuating population numbers. Competition is a selective pressure that directly affects relating organisms. Less food → competition → decline in species abundance. Symbiosis occurs when two or more organisms have a prolonged association that may benefit/ harm each member. Eg. parasitism, commensalism, mutualism.

                        symbiotic relationships is the term used for interactions in which a organisms live together in a close relationship that is beneficial to one.

•   MUTUALISM- both species in relo beneficial (+/+)
•   COMMENSALISM- one species if beneficial and other unaffected. (+/0) one receiving benefit is called commensal and one that doesn’t get affected is called host.

                – PARASITISM- one species beneficial and other suffers. (+/-) one receiving benefit is 

The ecological niches occupied by species

Ecological niche is the relational position of a population in an ecosystem and includes:

• What it eats.
• Where it moves.
• Habitat.
• Place in food chain.
• Abiotic + Biotic factors that affect it.

> NO two organisms can inhabit the same niche for long periods without some consequence for one of them.

Predicting consequences for populations in ecosystems due to predation, competition, symbiosis + disease. 

the part of the ecosystem that organisms occupies is called niche. Niche refers to all the resources that a species used. 3 types of niches

·   moderate interspecific (diff species) comp- realistic niche