Chapter 3.7 Ecosystems Flashcards
Def of population
Total number of all individual of the same species living in the same habitat at the same time
Def of community
Total number of organisms of all species living in the same habitat at the same time
What is a producer
An organism that produces its own food by photosynthesis
What is a primary consumer
The organism that eats the producer
What is secondary consumer
The organism that eats the primary consumer
Def of ecosystem
Interaction between biotic and abiotic factors
Types of biotic factors
Living components of an ecosystem
E.g
- food availability
- pathogens
-predictors
-mates
Types of abiotic factors
Light
- intensity
- hour of daylight
Soil features
- particle size
- water content
- pH
Temperature
O2 concentration
What is Interspecific competition
Competition between individuals of different species
E.g for food/ space/ nesting sites
What is intraspecific competition
Competition between organism of the same species
E.g for food/ mates/space/ nesting sites
Def of mean generation time
Time required for the number of cells to double
Calculation of mean generation time
Mean generation time = time
——————-
Number of generations
Draw graph to show growth of population with unlimited nutrients
Graph with positive gradient at increasing rate
(Exponential growth curve)
Explain exponential growth curve
Population double each generation
- seen in bacteria which divide by binary fission
Graph graph of growth of population with limited nutrients
S shapes curve with plateau being the carrying capacity
Def of carrying capacity
Maximum population that can be supported by habitat due to limiting factors (food, nesting sites, disease, predation)
Sketch growth curve of bacteria in a close system
(Nutrients only added at start and waste not removed)
See notes
And outline the 4 stages
Describe the 4 stages of bacteria growth in closed system
1) Lag Phase
No growth, synthesis of enzymes to metabolise available nutrients
2) Log Phase
Exponential growth (number doubles each generation)
3) Stationary Phase
Growth rate = death rate
4) Death Phase
Death rate > growth rate as nutrients runs out or waste accumulates
Suggest and explain causes for population increases
Plentiful food supply
- favourable climate for plant growth
- less competition with other species
Less predators
- decreases total number of predators
- increase population of alternative prey
Low disease
Plentiful breeding sites
- less competition with other species
General features of a predator prey graph
Curves are the same shape, but predator line is to the right of prey line
Predator numbers must always be smaller than prey numbers
What are density-independent factors
Factors that limit population sizes irrespective to density of the population
2 examples: natural disasters & human activity
List 4 density- dependent limiting factors and their effects on population size
inter-competition
Competition between individuals of different species for food/breeding sites
Intra-competition
Competition between individuals of the same species for food/mates/breeding sites
Predation
Larger the population: more predators, attracted/can be supported
Disease
Larger the population: more crowding, greater transmission of pathogens
What can density dependent limiting factors do?
- increase a population = positive relationship
- reduces population as it increases (killing individuals
- reduction is proportional to size of population
> larger population = more individuals killed by factor
Methods used to estimate population size
mark-release-recapture
1) capture a sample of animals from randomly assigned sites
2) count and mark all captured animals
3) release all captured animals back into habitiat
4) after a suitable time period, capture a second sample from same sites
5) count total number and number of marked animals
Population = total number 1st sample X total number 2nd sample
————————————————————————-
Number of marked in 2nd sample
Calculation of population size from mark release recapture
Population = total number 1st sample X total number 2nd sample
————————————————————————-
Number of marked in 2nd sample
Ethical issues considered with mark-release-recapture
Mark must not
- harm the animal
- make it more likely to be eaten by predators
What conditions needed to ensure mark-release-recapture is accurate
Marked animals not affected
Marked animals completely mix within population between sampling
Identical probability of capturing a marked or unmarked animal
Population is closed
No birth or death occur between sampling
Def of succession
Gradual and directional change in a community over time
Def primary succession
Succession that starts from bare ground with no living organism
Def of pioneer species
First plants to colonise the new habitat
Def of seres
Recognisable stages of succession which are characterised by the dominant plant species
Def of climax community
The final group of species found in the habitat
They are the most complex community, that can be supported, steady state
Def of secondary succession
+example
Gradual, directional change in a community over time that does not start from bare ground, some soil remains
+ e.g. after a fire or flood
Def of deflected succession
+ example
Human activity preventing climax community forming
+e.g. grazing farm animals or felling of trees
Why do plant species change over time by succession
Pioneer species change the environment by forming richer soils.
The plant’s dead leaves/roots form humus
humus - increases nutrient levels and improve water holding capacity
Pioneer are gradually outcompeted and replaced by other species that are better adapted to new conditions
Examples of pioneer species
Marram grass
Lichens
What are the initial hostile abiotic conditions that occur at beginning of succession
Limited water content -no soil to retain water
Few minerals/ nutrients - due to no soil
High light intensity - no plant cover
Exposed to wind and rain - no plant cover
High/ fluctuating temperatures
