Unit 2.2 Communities and ecosystems Flashcards
Community
a group of populations living and interacting with eachother in one area.
Photosynthesis
process by which green plants, algae, and certain bacteria convert carbon dioxide and water into glucose and oxygen, using sunlight as energy. This process is essential for producing the organic compounds and oxygen that sustain most life forms on Earth.
Chemical reactions:
6CO2 + 6H2O - (Sunlight) - C6H12O6 + 6O2
Ecosystem
An ecosystem is a community and the physical environment it interacts with.
- Terrestrial
- Freshwater (rivers, lakes and wetlands)
- Marine (sea, estuaries, salt marshes and mangroves)
RespIration
process where cells convert glucose and oxygen into energy, carbon dioxide, and water. It’s crucial for energy production in living organisms
a series of inputs, energy transformations and outputs
Chemical reactions:
C6H12O6 + O2 – Energy 12 H20 + 6 CO2
How can we model feeding relationships of a species in a system
food chains, food webs and ecological pyramids.
Food chain
A food chain is the flow of energy from one organism to the next
Producers
(autotrophs) make their own food from CO2 and water using energy from the Sun.
Consumers
(heterotrophs) cannot make their own food so they feed on other organisms to obtain energy and matter
Chemosynthetic organisms
producers that do not require sunlight to make their own food.
Trophic levels
Trophic level 1 Producer Grass
Trophic level 2 Primary consumer Grasshopper
Trophic level 3 Secondary consumer Mouse
Trophic level 4 Tertiary consumer Owl
Decomposers
(also heterotrophs) obtain their energy from dead organisms or feces or parts of an organism
provide a crucial
service for the ecosystem:
- They break down dead organisms
- They release nutrients back into the cycle
- They control the spread of disease
Food web
A complex network of interrelated food chains
Ecological pyramid
model of the quantitative differences (differences in numbers) between amounts of living material stored at each trophic level of a food chain.
- Pyramids of numbers
- Pyramids of biomass
- Pyramids of productivity
Pyramid of numbers
shows the number of individuals at each trophic level in a food
chain at one time.
The units are numbers per unit area.
Pyramid of productivity
shows the flow of energy in an ecosystem over a period of time, usually a year.
It is measured in mass or energy per square metre per year (kg/m^2y or kJ/m2y)
Pyramid of biomass
quantifies the amount of
biomass present at each
trophic level at a certain point in time.
They use units of mass per unit area (kg/m2 , g/m2)
Pyramid of numbers
Advantages vs Disadvantages
Advantages:
- Gives us a quick overview
- Useful for comparing population numbers in different seasons
Disadvantages
- No account is taken of the size of organisms, so
pyramids that involve large producers such as
trees are inverted
- Numbers can be too great to represent accurately
Pyramid of Biomass
Advantages vs Disadvantages
- Takes account of the size of organisms, so overcomes some of
the problems of pyramids of numbers - Only uses samples from populations, so difficult to measure biomass exactly
- Organisms must be killed to measure dry mass
- Seasonal variation leads to inverted pyramids
- Some animals have a lot of bone or shell, which
can distort the results
Pyramid of Energy
Advantages vs Disadvantages
- Shows energy transferred over a
period of time, so allows for different rates of production - Ecosystems can be compared easily
- Pyramids are never inverted
- Data is difficult to collect, as rate of biomass
production over time must be measured - Many species feed at more than one trophic level which can affect the results (this is true for all
pyramids)
Bioaccumulation
is the build-up of persistent pollutants within an organism or trophic level because it is not biodegradable
Biomagnification
is the increase in concentration of persistent pollutants along a food chain
DDT
- DDT is a synthetic chemical compound used as an insecticide, known for its effectiveness in killing mosquitoes and other pests.
- Introduced in the 1940s, DDT was widely used to combat diseases like malaria and typhus, and in agriculture to protect crops due to its effectiveness and low cost.
- DDT enters food webs primarily through agricultural runoff and accumulation in soil and water, where it is absorbed by plants and consumed by animals, leading to bioaccumulation and biomagnification.
- Still produced in a few countries
- Stockholm Convention on POPs: international environmental treaty, signed in 2001, aims to eliminate the production and use of persistent organic pollutants (POPs), including DDT.
- DDT can cause reproductive issues in birds (e.g., thinning eggshells) and fish, and can affect the nervous system of a wide range of wildlife.
- highly persistent in the environment, with a half-life that can range from 2 to 15 years, leading to long-term contamination of soil and water bodies.
