KS3
Ecosystems & Habitat
Around our world, we have different ecosystems and habitats that support animals and plants.
Find out what factors play an important part in healthy ecosystems.
Ecosystems and food chains
From the darkest depths of the oceans to the tallest mountain ranges and all across planet Earth, you can find many ecosystems and organisms that depend on each other.
Energy transfer
One of the ways they depend on each other is by consuming (eating) another organism. We call this a food chain. The arrows on a food chain represent the energy transferred from one organism to another.
Bottom of the food chain
At the start of a food chain, there is a producer. Usually, this will be a plant. Photosynthetic organisms such as plants and algae produce glucose, oxygen, and energy through photosynthesis.
Primary consumer
Primary consumers will eat the producer absorbing the energy. The primary consumer gets eaten by the secondary consumer, and so on.
Apex predator
At the top of the trophic levels is the apex predator. Apex predators are at the top and are not seen as prey by anything.
Food webs
A food web shows us that most organisms don't eat from just one food source.
In a habitat, there are many organisms for a consumer to choose from.
A fox will eat rabbits, frogs, and grass, but hawks will also eat frogs alongside snakes, mice, and other organisms.
Ecological sampling of ecosystems
An ecologist studies how many living organisms are in a habitat and how they interact. An ecologist in the UK earns around £29,900.
Learning about how a community interacts in a habitat will help us understand how to protect these species.
Counting populations in ecosystems
When trying to count the population of any species, scientists sample an area and estimate the population size. By estimating, scientists save money and time.
The information gathered helps show which species are thriving or near extinction.
There are many ways to sample a population, including quadrats, pooters, pitfall traps, and nets.
Measuring biodiversity
Quadrats can help to measure biodiversity or count a single species. Biodiversity is the measuring of a community within a habitat.
When using a quadrat, you can count individual specimens or measure the percentage that specimen covers per square.
Using a quadrat
When using a quadrat in a random or systematic habitat, sampling gets used depending on the data required.
Random sampling must be non-biased, meaning you cannot pick where you sample from, for example, an area with many or few samples.
Collecting results
To prevent bias in your experiment, divide the sampling area into a grid (ten by ten).
Use a random generator to give coordinates for your grid (This can be achieved by pulling numbers from a hat).
Collect the results and do this another ten times to get good results.
Systematic sampling
Systematic sampling is not random and occurs when scientists link environmental factors to population.
An imaginary line called a transect gets drawn in a specific part of the habitat, and counting occurs at regular positions.
Pitfall Traps
Pitfall traps are small holes dug into the ground to catch ground specimen. Sometimes food is placed in them to lure a species.
Pooters
Pooters (sometimes called an aspirator) are used to suck up small specimen such as fruit flies.
Nets
Nets are used to catch specimen in the air, long grass or in water.
Take care
When sampling using these techniques, organisms must not be hurt and must be returned to where they were found.
For example, with pitfall traps, rain can fill these up, killing organisms, so do keep an eye on them.
When collecting organisms, return the habitat back to its original location.
Pyramids of numbers
Pyramids of numbers are drawn with the producer at the bottom and consumers on top. The pyramid of numbers gets smaller moving up the pyramid because the energy gets lost in its surroundings, which means not all energy is transferred to the higher trophic levels. Sometimes the pyramid shape varies as the producer might be a large plant, such as a tree.
Pyramids of biomass
A pyramid of biomass shows the mass of all the organisms (including recently dead organisms) in grams or kilograms. Pyramids of biomass are always pyramid-shaped due to the amount of energy transferred to the next trophic level.
Kingdoms
All living organisms on Earth are carbon-based lifeforms. There are millions of different organisms, and scientists classify them to make studying each species easier.
A taxonomist in the UK earns an average of £32,000. A taxonomist studies taxonomy, which is the identification and classification of organisms. Carl Linnaeus was a Swedish Scientist in the 18th century who developed a classification system known as binomial nomenclature.
Binomial system
The binomial system helps us identify specific species. Species are named using Latin words bringing the genus and species part of their classification together. The binomial name for a wolf is Canis lupus, and for a human, it's Homo sapiens.
The modern technique for classification got developed over 200 years later when genetic analysis became available. This classification system splits 'domain' into three more groups and has some structural variations.
The Five Kingdoms
Plantae
The Plantae kingdom uses light to produce food by photosynthesis and stores this as starch. They are multicellular organisms and have Eukaryotic cells with cell walls made from cellulose.
Animalia
The Animalia kingdom stores its food as glycogen. Their cells are Eukaryotic cells having a nucleus alongside other membrane-bound organelles but no cell wall. All organisms of this kingdom are heterotrophic, which means they consume other consumers or producers.
Fungi
The fungi kingdom has no chloroplasts and stores its food as glycogen. They are either multicellular or unicellular organisms with Eukaryotic cells. The cell walls in this kingdom get made from chitin.
Protoctista
Protoctista cells acquire their nutrients through absorbing organisms or photosynthesis (some have chloroplasts). These Eukaryotic cells are single-celled organisms that can live in a colony, remaining single cells. These single-cellular organisms move using cilia, pseudopodia, or flagellum.
Prokaryotae
These prokaryotic unicellular organisms have no nucleus. They absorb nutrients through their cell membrane or produce nutrients through photosynthesis.
Adaptation of plants
Over millions of years, organisms have evolved to survive in their environment. These species (alongside successful reproduction) have advantages over other species in these habitats.
The location of a plant on our planet helps explain its adaptation.
Plants in water
Water-based plants are resistant to root rot, can float, or will have a height advantage meaning they can have most of their structure above the water. In boggy wetlands, nutrients can be low, so carnivorous plants such as the 'venus fly trap' catch insects to get their nutrients.
There are several different 'carnivorous' plant species. Many water-based plants have strong roots to anchor themselves, but others float on top of the water.
Adaptations
Other adaptations plants might have,
Needle leaves reduce water loss and provide protection.
Large leaves in low light leveled areas to maximize the amount of light caught.
Shallow roots absorb as much water as possible in dryer areas such as mountains and deserts.
Some plants can climb up others to maximize the amount of light they get. They might have sticky pads, hooks, or shoots that wrap onto things.
Mangroves
The mangroves have deep roots and filter out salt water into their leaves. Mangroves then get rid of the leaves when full of salt.
Cacti
Some plants (such as cacti) can break parts off, which self-roots for reproduction, meaning they don't need pollination.
Reproductive system
Many plants have flowers as their reproductive system. After pollination, plants grow seeds that disperse in one way or another.
Biodiversity and gene pools
When there is a range of species in a habitat, we refer to this as biodiversity. If there are only a few species (for example, deserts), we refer to this as less biodiverse. A rainforest is referred to as very biodiverse due to the number of species it has.
As humans interact with the environment and keep destroying it for farming (amongst other things), we reduce the biodiversity of our habitats and the planet. Conservation projects are reducing the impact of humans on the environment by protecting organisms and their habitats.
Preserving food chains
Conservation preserves food chains, prevents extinction, and allows us to learn more about these areas. Sometimes humans have introduced species to a habitat which causes a negative effect.
In the UK, the grey squirrel got introduced. As a larger species, they out-competed the red squirrels but also brought over a disease that killed off the majority of red squirrels. Conservation has started to bring the red squirrels back to the UK. The isle of Anglesey in Wales is one of several areas that are highly protected to make sure grey squirrels do not come anywhere near the red squirrels.
What are gene pools?
A gene pool is when the DNA of a species has a wide range of slight variations. Genetic variation is vital for the survival of a species, as it gives an organism advantage over other organisms. Over millions of years, these variations cause the evolution of new species.
Svalbard global seed vault is on an island off the coast of Norway. It is a seed bank that stores seeds from 4.5 million plant species.
A packet of seeds holds roughly 500 seeds totaling around 2.5 billion seeds. This vault is at a temperature of -18oC (255 Kelvin) and is an example of a gene bank.
Gene banks preserve genetic information for the future, maintaining biodiversity and preventing extinction.
A cryobank is similar to a seed bank. A cryobank stores embryos, sperm, and egg cells in liquid nitrogen (N2) for breeding programs.
Ecosystems and extinction
If a species isn't able to adapt to change, that entire species will die out, this is called extinction. Planet Earth has had five mass extinction events, the worst being 250 million years ago. 96% of sea life and 70% of land organisms died in this event, and recovery took millions of years, with many species never returning.
Captive breeding
Extinction is still occurring due to human activity. Some species no longer exist in the wild and can only be found in zoos. Scientists are undertaking programs such as captive breeding, which gradually increases the population with the ability to reintroduce them back into their natural habitat.
Captive breeding is brilliant for continuing a species, but it has problems. Biodiversity gets reduced due to a small genetic pool, and not all species will be able to return due to their reliance on humans for food.
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