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State the levels of organisation in an ecosystem.
Individual, population, community, ecosystem
What is an ecosystem?
The interaction between the living components and the non-living components
State the factors that plants may compete for
light
space
water
mineral ions from the soil
State the factors that animals might compete for
food
mates
territory
What is intraspecific competition?
competition within a species
What is interspecific competition?
Competition between different species
What is interdependence?
Different species in an ecosystem depend on each other for various resources, if one species is removed, the whole community may be affected
What is a stable community?
A community in which all the biotic and abiotic factors are balanced so that population sizes remain relatively constant
What are abiotic factors?
non-living factors
State the abiotic factors that may affect an ecosystem?
light intensity
temperature
moisture
soil pH and mineral content
wind intensity and direction
carbon dioxide level
oxygen level
Why might light intensity affect an ecosystem?
Different species of plants may have different optimum light intensities for growth.
Why does temperature affect an ecosystem
Different species of plants and animals may have different optimum temperatures for growth and survival.
How does soil pH affect an ecosystem?
Certain plants may grow better in either alkaline or acidic soil. Soil pH may affect the appearance of the plant eg. colour of hydrangea
How does moisture level affect an ecosystem?
Many plants cannot survive in waterlogged soil as their roots cannot respire Certain plants are adapted to high moisture levels
How does wind intensity affect an ecosystem?
Plant seeds are more likely to germinate in locations with lower wind intensity, which may also attract animals that depend on the plant to live nearby.
How does soil mineral content affection an ecosystem?
Most plants require a high level of soil minerals to grow well
Give an example of a type of plants that have adapted to low soil mineral content
Carniverous plants catch insects to compensate for the low level of soil mineral content
How does carbon dioxide concentration affect an ecosystem
Higher carbon dioxide concentration leads to more plant growth
How does oxygen concentration affect an ecosystem?
Aquatic animals cannot survive in areas with low oxygen concentration.
State the biotic factors that may affect an ecosystem.
food
new predators
new pathogens
competition
What are adaptations?
Features that enable organisms to survive in their living environment
What are organisms living in extreme environments called?
Extremophiles
Give three examples of extreme living environments
high temperature
high pressure
high salt concentration
State an example of where extremophile bacteria can be found.
In deep sea vents
Define population
A species that occupy the same habitat
Define habitat
the place in which an organism lives
Define community
populations of different species interacting
Define ecosystem
The interactions between the biotic and abiotic factors in an area
What do food chains show?
Food chains show the feeding relationships of different organisms and the flow of energy between the organisms.
Define biomass
The total mass of living material
What are trophic levels?
The stages in a food chain
What do the arrows in a food chain represent?
The direction of biomass transfer
Describe a simple food chain
producer --> primary consumer --> secondary consumer --> tertiary consumer
What is a producer?
An organism that makes its own food
What types of organisms are primary producers?
Photosynthetic organisms like green plants and algae that trap energy from the sun
What is a primary consumer?
An organism that feeds on producers.
What is a secondary consumer?
an organism that feeds on primary consumers.
What is a tertiary consumer?
An organism that feeds on secondary consumers
what is a predator?
A consumer that kills and eats other animals
What is prey?
an animal that is killed and eaten by another animal
Describe the pattern of predators and prey in a stable community
The numbers of predators and prey rise and fall in cycles
Why are producers the first trophic level?
Producers provide all biomass for the food chain (via photosynthesis)
The rest of the food chain involves the transfer of this biomass
What piece of apparatus is used to measure the abundance and distribution of organisms in an area?
Quadrat
What piece of apparatus is used to study the distribution of organisms across a gradient
Belt transect
When considering the abundance of organisms, what is meant by the term "mean"?
The average number of organisms
Describe how materials cycle through the living and non-living components of an ecosystem?
organisms take in elements form their surroundings
elements converted to complex molecules which become biomass
elements transferred along food chains
elements returned to environment during excretion and decomposition
give three molecules which are cycled through ecosystems
Oxygen
Carbon dioxide
water
Describe the carbon cycle
plants fix carbon dioxide into organic molecules during photosynthesis
the organic carbon-containing molecules are passed onto organisms that eat the plant
carbon dioxide is released back into the atmosphere by respiration from plants and animals
burning fossil fuels also releases carbon dioxide into the atmosphere
Why is the carbon cycle important?
Carbon-containing molecules such as glucose are important for living organisms to grow and provide energy for vital functions within cells.
Describe the water cycle
Water from lakes and oceans evaporates.
The evaporated water condenses into clouds and returns to earth as precipitation.
The water from precipitation is useful for life on land.
The water then returns to rivers and oceans through surface runoff.
Why is the water cycle important?
Living organisms require water and the water cycle provides organisms on land with a continuous supply of water.
Why are microorganisms important for the cycling of materials through an ecosystem?
Microorganisms return carbon to the environment by releasing carbon dioxide through respiration while they decompose dead matter. The decomposition of dead matter in soil returns mineral ions to the environment for other organisms to use
How can different temperatures be bad for certain communities?
if the temperature is too low, growth will be sower as organisms will use more energy to stay warm
If the tempreature is too high, organisms can die and water will become limited as evaporation increases
How can changes in water levels affect ecosystems?
Animals may have to migrate to find water.
Melting ice caps may destroy the habitats of some animals (either animals living in icy regions or by sea level rise).
How can atmospheric gases affect ecosystems?
Some organisms cannot survive when certain gases are present
Polluted water can cause illness to animals that drink it
What detrimental impacts can sulfur dioxide have on the environment?
formed when fossil fuels containing impurities are burnt
sulfur dioxide can dissolve in water to form acid rain which can erode buildings and pollute water sources
What detrimental impacts can carbon monoxide have on the environment?
carbon monoxide is formed from the incomplete combustion of fossil fuels
carbon monoxide binds irreversibly to haemoglobin which prevents it from carrying oxygen
too much exposure can cause unconsciousness and death
Name 4 green house gases
water vapour
carbon monoxide
nitrus oxide
methane
Give 3 human activities that contribute to greenhouse gases
burning fossil fuels
deforestation
large scale livestock farming
How do greenhouse gases lead to global warming?
Greenhouse gases allow heat from the sun to enter the atmosphere.
The gases act as a 'blanket' and trap the heat in the atmosphere.
State 3 negative consequences of global warming
Sea level rise caused by melting icebergs.
Disrupted farming and agriculture.
Increased spread of diseases in warmer climates.
What is biodiversity?
The variety of different species of organisms on Earth or within an ecosystem
What is the importance of biodiveristy?
To maintain the stability of an ecosystem
How does biodiveristy ensure the stablity of an ecosystem
It reduces the dependence on particular species for resources, so that even if one species is removed another can still survive
Why have humans' consumption of resources and waste production increased?
rapid increase in human population
increase in standard of living
Where does pollution occur?
air
land
water
State an example of water pollutants
sewage
fertiliser -chemicals
How does eutrophication occur?
Fertiliser from farms pollute the water, causing excessive algae growth, depleting the oxygen in the water, causing other plants and animals to die. Dead plants are decomposed by bacteria and the oxygen level decreases further.
State an example of air pollutants
smoke
acidic gases
State an example of land pollutants
Landfill waste
Chemicals
Which human activities reduce the land available for animals and plants?
building
farming
quarrying
disposing of waste
Why have peat bogs been destroyed?
To produce compost to increase food production.
Why does the destruction of peat bogs greatly contribute to the greenhouse effect?
Peat bogs are stores of carbon and burning them releases a large volume of carbon dioxide into the atmosphere
Why have large-scale deforestation activities occurred?
To provide land for cattle or rice fields
to grow crops to produce biofuels
What is the greenhouse effect?
Greenhouse gases trap energy from the Sun as heat in the atmosphere, keeping the temperature on earth suitable for life.
What causes global warming?
The increase in levels of greenhouse gases causing the temperature on earth to increase
What are the harmful effects of deforestation?
Destruction of many animals' habitats
Releases large amounts of greenhouse gases
State the consequences of global warming
Rising sea levels
Melting polar ice caps
Changing weather patterns
Migration of animals to find suitable habitats
Tropical diseases becoming more common
Extinction of species
Describe the steps taken to maintain biodiversity?
Breeding programmes for endangered species.
Protection and rebuilding habitats.
Replanting field margins and hedgerows.
Reduce deforestation.
Reduce carbon dioxide emissions.
Recycling rather than disposing in landfills.
What is the purpose of replanting hedgerows and field margins?
There is higher biodiversity in the margins than the field that they surround
What is homeostasis?
Homeostasis is the maintenance of a constant internal environment in order to maintain optimum conditions for enzyme and cellular function
Give examples of conditions maintained by homeostasis in the body?
blood glucose concentration
body temperatures
water levels
What two types of responses are used in body control systems?
Nervous and chemical
What three components do all control systems have?
receptors
coordination centres
effectors
What is the function of a receptor?
Receptors detenct a change in the environment (stimuli)
What is the function of coordination centres?
Coordination centres obtain and process information from receptors
What is the function of an effector?
Effectors (muscles or glands) bring about responses to stimuli
What is the function of the nervous system?
The nervous system allows the body to react to its surroundings and coordinate an appropriate response
How does a stimulus lead to a response being carried out by the body?
Stimulus is converted into an electrical impulse by the receptors
The electrical impulse passes along sensory neurones to the central nervous system
the CNS coordinates an appropriate responses and an electrical impulse is sent along motor neurones to the effector, which carries out the response
What sequence of events describes how the nervous system works?
Stimulus --> receptor --> coordinator --> effector --> response
What is a reflex action?
A reflex action is an automatic and rapid response which does not involve any conscious input from the brain
Describe how a reflex action occurs via a reflex arc
the stimuli is detected by a receptor
an electrical impulse passes along a sensory neurone to the spinal cord (CNS)
at a synapse between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone
the same process occurs at a synapse between a relay neurone and a motor neurone
at the effector and appropriate response is carries out
What is the difference between a reflex pathway and a conscious pathway?
Within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord/ unconscious parts of the brain. In a conscious pathway, the coordination centre is in the conscious part of the brain
Give the name of the body's coordination system which involves hormones
The endocrine system
What is a hormone?
A hormone is a chemical messenger secreted by a gland. It travels in the blood to a target organ, where it causes a response
What type of organ secretes horomones?
Glands
Which gland controls many other glands in the body?
The pituitary gland
Why is the pituitary gland called the master gland?
It secretes a wide range of hormones, some of which may stimulate other endocrine glands
What is the role of the pituitary gland in the endocrine system?
secretes human growth hormone - controls human growth
stimulates the thyroid gland
stimulates ovulation and the production of eostrogen in the ovaries
stimulates the production of sperm and testosterone in the testes
What is the role of the thyroid gland in the endocrine system?
Secretes the hormone thyroxine - controls metabolism, heart rate and body temperature
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