Topic 7 - Genetics, populations, evolution and ecosystems Flashcards
(17 cards)
What is an ecosystem
All the living and non living components in an area
Define Biosphere
The sum of all the ecosystems on earth
Define carrying capacity
The maximum population in a habitat that an ecosystem can sustainably support
What factors can affect the carrying capacity
abiotic factors- temperature, pH levels, water availability
Biotic factors - predation, interspecific competition, intraspecific competition
Define intraspecific competition
Competition within the same species
Define interspecific competition
Competition between different species
What do organisms compete for
Food, mates, terratory
Define the term ecological niche
An organisms role in a habitat based on its adaptations to biotic and abiotic factors
Why do different ecological niches mean different species can coexist
Each species has specific adaptations which enable them to access different food sources so they can occupy the same habitat while reducing interspecific competition
Define microhabitat
smaller units within each habitat, each with their own microclimate
What happens in the lag phase (1)
Bacteria are acclimatising, the population remains steady no reproduction but bacteria grow in size
What happens in the log phase (2)
Bacteria reproduce at the maximum rate sine all the nutrients and oxygen are available so no limiting factors, bacteria doubles each generation
What happens in the stationary phase (3)
Growth stops almost completely due to limiting factors such as oxygen, water, nutrients. The culture is at its maximum population density. The death rate and reproduction rate is equal
What happens in the death phase (4)
The death rate exceeds the reproduction rate due to build up of waste (eg. urea and carbon dioxide) and exhaustion of nutrients
What is the competitive exclusion principle
Two species which compete for the same limited resource cannot coexist at the same population size (so the species which is better adapted will dominate)
What two microorganisms were used
Paramecium aurelia and paramecium caudatum
Explain what happened between P.aurelia and P.caudata
P.aurelia used the limited resource more effectively so had a higher population therefore the P.caudata didn’t have access to the food source hence they couldn’t grow and reproduce hence died whilst the other bacteria dominated and reached its maximum population.
