7 Flashcards
population
the total number of individuals of onespecies in an ecosystem
community
all the plants andanimals living in an ecosystem
habitat
where a living organismlives in an ecosystem
Biodiversity
the range of different plant and animal species living in an ecosystem
niche
the particular place or role that an organism has in its own ecosystem
ecosystem
An ecosystem is defined as the interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of the environment.
They may be natural (oceans, rainforest) or artificial (fish farms or planted forests)
Biotic factors
Caused by living organisms affecting other populations in their ecosystems
* Food availability
* New pathogens
* New predators
* Competition / Species outcompeting one another
Abiotic factors
Physical, non-living conditions that affect the distribution of an organism
* Temperature
* Light intensity
* Oxygen levels (for organisms living in water)
* Carbon dioxide levels, soil pH and mineral content for plants
* Moisture levels
* Wind intensity and direction
* soil ph & mineral content
plants compete for…
Light
Space
Water
Mineral ions
Animals compete for…
Food
Water
Mates
Territory
If one species is more successful than the other. The less successful species may:
Do nothing and become extinct
Stay in its habitat but adopt new survival strategies
Move to another area looking for resources
Why do organisms compete?
- Species can only survive if they have sufficient resources, therefore they compete for available resources in their habitat
- Animals and plants that get more of the resources are more successful than those that get less.
- Successful organisms are more likely to survive and reproduce so the size of their population is more likely to increase
Interspecific competition
competition between different species
Intraspecific competition
competition within one species. May result in territorial behaviour
Intraspecific competition is most common as animals try to avoid competition with others if they can.
interdependence
Within a community each species depends on other species for food, shelter, pollination, seed dispersal etc. If one species is removed it can affect the whole community.
A stable community is one where all the species and environmental factors are in
balance so that population sizes remain fairly constant.
Adaptations
feature that helps an organism to increase its fitness – the ability to survive and reproduce in its environment
Behavioural adaptations
Behavioural adaptations of animals are behaviours which give them an advantage.
burrowing to remain cool
mating rituals
migration
hibernating
Physiological adaptations
Physiological adaptations of animals are processes which allow them to compete.
temperature regulation
production of venom
Structural adaptations
Structural adaptations of animals are the physical features which allow them to compete.
claws
camouflage
blubber
eyesight and hearing
What are trophic levels?
Trophic levels are the different stages of a food chain.
They consist of one or more organisms that perform
a specific role in the food chain.
Trophic levels are named after their location in the food chain using numbers. The first level is called trophic level 1. Each level after that is numbered in order based on how far along the food chain the organisms in the trophic level are. You need to know the differences between the different trophic levels:
Trophic level 1
Trophic level 1 contains producers. Producers
are the organisms at the starting point of a food
chain, e.g. plants and algae. They’re called
producers because they make their own food by
photosynthesis using energy from the Sun.
Trophic level 2
Trophic level 2 contains primary consumers.
Herbivores that eat the plants and algae are primary
consumers. Herbivores eat only plants and algae.
Trophic level 3
Trophic level 3 contains secondary consumers.
Carnivores that eat the primary consumers are
secondary consumers. Carnivores are meat eaters.
Trophic level 4
Trophic level 4 contains tertiary consumers.
Carnivores that eat other carnivores (the secondary
consumers) are tertiary consumers. Carnivores that
have no predators are at the top of the food chain,
so they’re always in the highest trophic level.
They’re known as apex predators.
Decomposers
Decomposers such as bacteria and fungi play an important role in ecosystems.
They decompose any dead plant or animal material left in an environment.
They can do this by secreting (releasing) enzymes that break the dead
stuff down into small soluble food molecules. These then diffuse into the
microorganisms. This process also releases nutrients into the environment,
which the producers need in order to grow.
What are food chains?
Food chains show what’s eaten by what in an ecosystem.
Food chains always start with a producer. Producers make (produce) their own food using energy from the Sun. Producers are usually green plants or algae - they make glucose (a sugar) by photosynthesis.
Energy is transferred through living organisms in an ecosystem when organisms eat other organisms. Producers are eaten by primary consumers. Primary consumers are then eaten by secondary consumers and secondary consumers are eaten by tertiary consumers.
Predator-prey cycles
Consumers that hunt and kill other animals are called predators, and their prey are what they eat. In a stable community containing prey and predators (as most of them do of course), the population of any species is usually limited by the amount of food available. If the population of the prey increases, then so will the population of the predators. However as the population of predators increases, the number of prey will decrease.
Predator-prey cycles - example
Predator-prey cycles are always out of phase with each other. This is because it takes a while for one population to respond to changes in the other population. E.g. when the number of rabbits goes up, the number of foxes doesn’t increase immediately because it takes time for them to reproduce.
Pyramids of biomass
Pyramids of biomass show the relative mass of each trophic level.
There’s less energy and less biomass every time you move up a
stage (trophic level) in a food chain. So there are usually fewer
organisms every time you move up a level too, as there’s less
energy available to support them.
Pyramids of biomass and number example
One oak tree can feed 2000 caterpillars. These caterpillars are eaten by around 90 bluetits. 1 sparrowhawk can eat around 90 bluetits.
One oak tree can feed 2000 caterpillars. These caterpillars are eaten by around 90 bluetits. 1 sparrowhawk can eat around 90 bluetits.
Pyramid of biomass disadvantages
- It can be difficult to catch organisms to calculate their mass
- Organisms need to be killed to calculate their dry mass
- Biomass varies depending on season etc.
- Some organisms feed on multiple trophic levels, e.g. omnivores
How is biomass transferred?
Energy from the Sun is the source of energy for nearly all life on Earth.
Producers, such as green plants and algae, use energy transferred by
light from the Sun to make food (glucose) during photosynthesis.
Of the energy that hits these producers, only about 1% is transferred
for photosynthesis. Some of the glucose is used by the plants and algae
to make biological molecules. These biological molecules make up
the plant’s biomass - the mass of living material. Biomass stores energy.
Biomass is transferred through a food chain in an ecosystem when organisms eat other organisms. However, not much biomass gets transferred from one trophic level to the next. In fact, only about 10% of the biomass is passed on to the next level.
How is biomass lost - Uneaten material
- Organisms don’t always eat every single part of the organism they’re consuming. For example, some material that makes up plants and animals is inedible (e.g. bone). This means that not all the biomass can be passed to the next stage of the food chain.
- Also some organisms die before they’re eaten, so their remains are left to decay and their energy doesn’t get passed along the food chain (instead the energy gets passed to the microorganisms that break down the remains).
How is biomass lost - Waste products
Organisms don’t absorb all of the stuff in the food they ingest (take in).
The stuff that they don’t absorb is egested (released) as faeces (poo).
Some ingested biomass is converted into other substances that are lost as waste.
For example, organisms use a lot of glucose (obtained from the biomass) in
respiration to provide energy for movement and keeping warm, etc. rather than
to make more biomass. This is especially true for mammals and birds, whose
bodies must be kept at a constant temperature which is normally higher than
their surroundings. This process produces lots of waste carbon dioxide and
water as by-products. Urea is another waste substance, which is released in
urine with water when the proteins in the biomass are broken down.
biomass calculations
You can work out how much biomass has been lost at each level by taking away the biomass that is available
at that level from the biomass that was available at the previous level.
You can also calculate the efficiency of biomass transfer between
trophic levels using this formula:
The water cycle
The water here on planet Earth is constantly recycled. Energy from the Sun
makes water evaporate from the land and sea, turning it into water vapour.
Water also evaporates from plants - this is known as transpiration. The warm water vapour is carried upwards (as warm air rises).
When it gets higher up it cools and condenses to form clouds. Water falls
from the clouds as precipitation (usually rain, but sometimes snow or hail)
onto land, where it provides fresh water for plants and animals. It then
drains into the sea, before the whole process starts again.
the carbon cycle - Carbon is taken out of the air
The whole carbon cycle is “powered” by photosynthesis. CO2 (carbon dioxide) is removed from the atmosphere by green plants and algae, and the carbon is used to make glucose, which can be turned into carbohydrates, fats and proteins that make up the bodies of the plants and algae.
the carbon cycle - Carbon moves through food chains
Some of the carbon becomes part of the fats and proteins in animals when the plants and algae are eaten. The carbon then moves through the food chain. The energy that green plants and algae get from photosynthesis is transferred up the food chain.
When plants, algae and animals die, other animals (called detritus feeders)
and microorganisms feed on their remains. Animals also produce waste, and
this too is broken down by detritus feeders and microorganisms.
the carbon cycle - Carbon is returned to the air
Some carbon is returned to the atmosphere as CO2 when the plants, algae,
animals (including detritus feeders) and microorganisms respire. Also CO2
is released back into the air when some useful plant and animal products,
e.g. wood and fossil fuels, are burnt (combustion).
carbon cycle diagram
simple biogas generator example
Whether a generator is big or small, or for batch or continuous use, it needs to have the following:
- an inlet for waste material to be put in,
- an outlet for the digested material to be removed through,
- an outlet so that the biogas can be piped to where it is needed.
The increasing human population
The increase in human population has had an enormous effect on our environment. The future for species on Earth depends on maintaining good biodiversity. Any human activities are reducing biodiversity.
- More land is needed for building houses, shops, roads etc. This destroys habitats and reduces biodiversity
- More land needs to be cleared (deforestation) for farming to produce food. This destroys habitats and reduces biodiversity of plant and animal species
- We dig up land to make quarries to obtain rocks and metal ores. This reduces land available for organisms
- Human waste pollutes the environment
greenhouse effect
The temperature of the Earth is a balance between the energy it gets from the Sun and the energy it radiates back out into space. Gases in the atmosphere naturally act like an insulating layer. They absorb most of the energy that would normally be radiated out into space, and re-radiate it in all directions (including back towards the Earth). This increases the temperature of the planet. It’s called the greenhouse effect.
If this didn’t happen, then at night there’d be nothing to keep any energy in, and we’d quickly get very cold
greenhouse gases
There are several different gases in the atmosphere which help keep the energy in. They’re called “greenhouse gases”, and the main ones whose levels we worry about are carbon dioxide (CO₂) and methane - because the levels of these two gases are rising quite sharply.
The Earth is gradually heating up because of the increasing levels of greenhouse gases this is global warming. Global warming is a type of climate change and causes other types of climate change, e.g. changing rainfall patterns.
