Ecosystems Flashcards
What is a biotic factor?
Anything that influences populations that’s results from another organism’s activity
(Can be currently living or once lived)
What is meant by dynamic?
Constantly changing
What are the 3 types of changes in ecosystems?
Cyclic eg. Predator/prey populations
Directional (long lasting, irreversible) eg. Erosion of a coastline
Unpredictable/erratic changes eg. Effects of lighting or hurricanes
What is meant by competition?
When 2 or more individuals share a limited resource
What is meant by abiotic factors?
Any physical or chemical (non-living) factor that influences populations
What is meant by a niche?
A niche is the role of each species in an ecosystem eg. What it eats, excretes and how it reproduces
Why can’t 2 organisms fill the same niche?
2 species can’t fill the same niche as one species will always outcompete the other
What is meant by an ecosystem?
An ecosystem is a community of animals, plants and bacteria, interrelated with the physical and chemical environment
What is a habitat?
The place where an organism lives
What is a biotic factor?
Anything that influences populations as a result of an organisms activity (currently living or once lived)
Example of biotic factors
Predation
Disease
Competition for food, mates, territory
What 3 types of change in ecosystems affect population size?
Cyclic changes
Directional changes
Unpredictable/erratic changes
What are cyclic changes?
Repeat in rhythm
Eg. Tides, Predator/prey populations
What are directional changes?
Go in one direction and are long lasting
Eg. Erosion of a coastline
What are unpredictable/erratic changes?
Changes that come unexpected
Eg. Effects of lightning/ hurricanes
What is biomass?
The mass of living material present in a particular place or in particular organisms
How do you calculate dry mass?
1)Collect and kill the organisms
2)Put them in an oven at 80°c so water evaporates but material won’t disintegrate
3) Use a calorimeter to measure energy content
What is ecological efficiency?
The efficiency with which biomass or energy is transferred from one tropic level to the next
What is gross primary productivity?
The total solar energy that plants convert to organic matter
How to calculate ecological efficiency?
Energy/biomass available after transfer
__________________________________________
Energy/biomass available before transfer
X100
What is assimilation?
The process by which plants and animals absorb chemicals
• Nitrates (Soil —> Plant)
•Ammonium ions (Soil —> Plant)
•Amino acids (Plants —> Animals)
What is nitrogen fixation?
The process of breaking a nitrogen molecule (N2) apart and making new nitrogen-containing compounds
1) Biological fixation by certain microbes
2) Atmospheric fixation by lightning
3) Industrial fixation (Haber process)
What is decomposition?
The breakdown of dead and waste matter. Organic matter —> inorganic matter.
Eg. Carbohydrates, lipids, proteins, nucleic acids —> CO2, Water, ammonium
What is ammonification?
The process by which decomposers convert nitrogen containing compounds (proteins) in dead organisms, into ammonium containing compounds
What is denitrification?
Denitrification converts nitrates to nitrogen gas, replenishing the atmosphere.
Pseudomas bacteria are the agents of denitrification. They require anaerobic conditions
What is nitrification?
The two-step process by which ammonium containing compounds are converted into nitrates
1) nitrosomonas bacteria oxidise ammonium to nitrites (NO2-)
2) Nitrobacter bacteria oxidise nitrites to nitrates (NO3-)
True or false? Nitrogen is inert.
True, nitrogen is inert meaning plants must secure their nitrogen in ‘fixed’ form
What is an autotroph?
Organisms that produce their own food.
Producers
What is a photoautotroph?
Organisms that produce their own food via photosynthesis using light energy
Eg. Plants
What is a chemoautotroph?
Organisms are that produce their own food using energy obtained from the soil.
Eg. Nitrosomonas and nitrobacter
What is a heterotroph?
Organisms that consume other organisms for food.
Consumers
Eg. Animals
What is a saprotroph?
Organisms which feed on dead/decaying matter
Decomposers
Eg. Bacteria and fungi
What microbes are responsible for nitrogen fixation (biological)?
Azotobacter and Rhizobium
They both have nitrogenase enzymes to convert nitrogen to ammonia (forms ammonium ions in solution). Plants then use the ammonium ions to make amino acids. Nitrogenase enzymes work in anaerobic conditions
Where are Azotobacter found?
They are free-living
Where are rhizobium found?
They live in the root nodules of legumes.
They have a symbiotic mutualistic relationship. Rhizobium provide legume with ammonium in exchange for carbohydrates
What does detritus mean?
Detritus = dead and decaying material
What does inert mean?
Not very reactive. Nitrogen is inert because of its triple bond.
What are detritivores?
Organisms that break down detritus (dead and decaying material) into smaller pieces of organic material.
This increases the SA available for decomposers.
Eg. Woodlice and earthworms
What is interspecific competition?
Competition between individuals of DIFFERENT species
What is intraspecific competition?
Competition between individuals of the SAME species
What is the competition exclusion principle?
Where two species are competing for limited resources, the one that uses the resources most effectively will ultimately eliminate the other
Define preservation
Keeping species and habitats as they are now
Focuses on eliminating human effects and keeping things ‘natural’
Define conservation
A more active management process involving human intervention
Focuses on maintaining and improving biodiversity and using resources sustainably
What are threats to biodiversity?
Hunting for food/sport
Poaching
Pollution
Climate change
What can be done to maintain biodiversity?
Control predators/poachers
Captive breeding
Preserve habitats
Restrict dispersal of individuals via fencing
What is coppicing?
Where a tree is cut close to the ground.
Shoots then emerge and mature from the trunk.
The shoots can then be cut and used for fencing, firewood or furniture
What is rotational coppicing?
Where coppicing takes place a section at a time. Maintains a consistent supply of wood and maintains biodiversity
What is pollarding?
The same as coppicing however the trunk is cut higher up to prevent deer from eating the emerging shoots
What are the problems of overfishing?
Juvenile fish are caught
Bycatch (unwanted species are caught)
Too many of one kind of fish are caught, leading to a drastic decline in population
What are fishing quotas?
A limit placed on the numbers of certain species of fish allowed to be caught in a particular area
What are the issues of large scale timber production?
Soil is susceptible to erosion
Soil mineral levels are reduced
Habitats are destroyed
What occurs at the lag phase on a population growth curve?
Population growth rate is low. There are a few widely dispersed individuals, limiting availability of mates
What occurs at the exponential growth phase on the population curve?
Population grows at its maximum rate (biotic potential).
Birth rate > Death rate
What occurs at the transitional phase on the population curve?
As the population grows, environmental resistance increase. Competition for resources increases, slowing the growth rate
What occurs at the plateau phase on the population curve?
The population reaches the maximum size the ecosystem can sustain. This is called the carrying capacity (K).
The population remains roughly stable in a constant environment
Examples of biotic factors
Predators
Disease
Competition
Examples of abiotic factors
Temperature
Light
Ph
Humidity
Examples of density independent limiting factors
Temperature
Rainfall
Salinity
Natural disaster
Examples of density dependent limiting factors
Food
Shelter
Water
Light
Mates
Oxygen
What is plagioclimax?
It Is the final stage of succession when it has been deflected by humans or another outside factor
Describe the difference between primary and secondary succession
Primary succession occurs on bare rock/sand without soil. Whereas secondary succession takes place where soil is present but no plants are.
Secondary succession is much faster
What is deflected succession?
Where human activities halt the natural flow of succession, preventing the ecosystem from reaching a climax community
True or false? Primary succession is faster than secondary succession
False
Secondary succession is much faster as it takes place in areas where soil is already present
Give an example of a tertiary coloniser
Ferns
Give an example of a secondary coloniser
Moss
What is a climax community?
A community in which population of plants/animals remain stable and there is a range of species
Where does primary succession take place?
It begins in a place without any soil or organic material present
Eg. Sides of volcanoes, sand dunes, landslides
What are pioneer species?
Species adapted to harsh abiotic conditions. And through their death and decomposition, change the abiotic factors to become less harsh.
Eg. Lichen
What are the name of the steps of succession?
Seral stages
What are the disadvantages of pioneer species’ such as lichen?
They may alter the environment making it less suitable for other species with different adaptations
What are some key features of pioneer species?
Reproduce asexually - quickly growing population
Rapid germination of seeds
Can photosynthesise
Tolerance to extreme conditions
What are some key features of marram grass (a pioneer species)?
Deep roots
Tolerates salty environments
Curled leaves to store water
What are lichen?
They are a pioneer species that is a stable symbiotic association between a fungus and algae.
The algae photosynthesise whilst the fungus provides protection and keeps it from drying out.
True or false? Lichen only reproduce asexually
False
They can reproduce EITHER sexually OR asexually
Define succession
The change in an ecological community over time
What happens when pioneer species die and decompose?
They form a thin layer of soil called humus which allows other small plants to grow
