ECOLOGY

• the study of the inter-relationships between organisms and their environment, including both the living and non-living factors
  

ECOSYSTEMS

• dynamic systems made up of a community and all the non-living factors of its environment
• TWO MAJOR PROCESSES:

- the flow of energy through the system

- the cycling of elements within the system

POPULATIONS

• all the individuals of the same species living in one place at a particular time
  
• CARRYING CAPACITY: the given size of a population that an ecosystem can support
• WHAT AFFECTS THE SIZE OF A POPULATION?

- abiotic factors

- interactions between organisms (competition, predation)

COMMUNITIES

• the populations of different species living in one place at a particular time

HABITAT

• the place where an organism normally lives, characterised by its physical conditions and the other organisms present within it
• MICROHABITATS: the smaller units within a habitat where organisms immediately live (e.g. the mud at the bottom of a stream)

NICHE

• the role of an organism within its environment - where it lives, what it does there, the abiotic + biotic conditions to which an organism is adapted for survival
• COMPETITIVE EXCLUSION PRINCIPLE: no two species can occupy the same niche - one will always be more adapted for survival and thus cause the other's removal from the environment

POPULATION SIZE

PLOTTING GROWTH CURVES

• we use logarithmic scales as population numbers are often too high to accurately plot on a graph

POPULATION GROWTH OF MICROORANISMS

1, LAG PHASE - few bacteria to begin with so binary fission doesn't cause significant growth, cells have to grow before they can divide

2. LOG PHASE - exponential growth occurs as there are no limiting factors 

3. STATIONARY PHASE - limiting factors begin to arise, causing the death rate to equal the birth rate and stopping overall population grwoth. The population remains at its carrying capacity.

4. DEATH PHASE - limiting factors become unsustainable, death rate exceeds the birth rate and overall population decreases

ABIOTIC FACTORS AFFECTING POPULATION SIZE

• temperature - enzyme action, energy required to maintain body temperature in warm-blooded animals
• light - required for photosynthesis, more light = more plants = more food
• pH - enzyme action
• water + humidity - transpiration rates, only those adapted to survive in such conditions will do so

COMPETITION

INTRASPECIFIC COMPETITION

• individuals of the same species compete with each other for resources (food, water, breeding sites)
• the greater the availability of these resources, the greater the population size and visa versa

INTERSPECIFIC COMPETITION

• individuals of different species competer with one another for resources
• one species normally has a competitive advantage ovr another, causing that species' population to increase and the others to diminish 
• if the conditions do not change, the population of the inferior species will be removed entirely - COMPETITIVE EXCLUSION PRINCIPLE

PREDATION

• occurs when one organism is consumed by another

LAB CONDITIONS

the predator will eliminate the prey as the range of the habitat is limited to the lab

NATURAL CONDITIONS

the area over which the population can travel is greater and…