GCSE Science B2 Revision

A NATURAL ECOSYSTEM is one where humans don't control the processes going on within it.

Woodlands and lakes are natural ecosystems.

An ARTIFICIAL ECOSYSTEM is one where humans deliberately promote the growth of certain living organisms and get rid of others which threaten their well-being.

Greenhouses and fish farms are artificial ecosystems

Organisms > Kingdoms > Genus > Species

A species is a group of closely-related organisms that can breed to produce fertile offspring

Vertebrates are animals with a backbone and an internal skeleton. Invertebrates don't have this.

Vertebrates are divided into 5 groups called classes - fish, amphibians, birds and mammals.

Fish - scales and gills for gas exchange.

Amphibians - exchange gas partly through their skin, it has to be permeable and moist.

Reptiles - more adapted to living on land, dry scaly skin to stop them from loosing water.

Birds - they can fly and have feathers to help them, a beak for catching prey.

Mammals - fur to keep warm, give birth to young and produce milk to feed young.

The binomial system gives everything a two-part name.

Humans are known as Homo sapiens. 'Homo' is the genus and 'sapiens' is the species.

Unrelated species may have familiar features because they may share a recent ancestor so they are closely related in evolutionary terms.

Species that are very different genetically may also end up looking alike. Sharks are fish, dolphins are mammals but because they both live in water they have developed similar bone structures which make them adapt for swimming.

Keys are used to identify creatures.

Quadrat - a square frame enclosing a known area. Used to count the amount of organisms inside of it,

Nets - good for catching flying insects.

Pitfall traps - used to catch insects that walk across the ground. The insects fall into the trap and are trapped.

Pooters - used to **** up individual insects chosen by the user.

The sample size affects the accuracy of the estimate.

The sample may not be a representative of the population.

Photosynthesis uses energy from the Sun to change carbon dioxide and water into glucose and oxygen.

Carbon dioxide + Water --> Glucose + Oxygen

6CO2 + 6H20 --> C6H12O6 + 6O2

Glucose is soluble, which makes it really good for transporting to other places in the plant. It's also a small molecule - so it can diffuse in and out of cells easily.

Glucose is used in a plant for: -

• Respiration
• Making Cell walls
• Stored in seeds
• Stored as starch
• Making proteins

Starch is insoluble, which makes it much better for storing - it doesn't bloat the storage cells by drawing water in like glucose would.

Not enough LIGHT slows down the rate of photosynthesis

Too little CARBON DIOXIDE slows down the rate of photosynthesis

The TEMPERATURE has to be just right - 45°C or more then the enzymes will be destroyed(denatured) and the rate of photosynthesis rapidly decreases

Photosynthesis and respiration are OPPOSITE processes.

Photosynthesis > requires energy.

Respiration > releases energy.

Photosynthesis only happens during the day but plants respire all the time, day and night.

Population size is limited by: -

• The total amount of food/nutrients available
• The amount of water available
• The amount of light available ( for plants. )
• The quality and amount of shelter available

Animals and plants of the same species and of different species will COMPETE against each other for these resources. They all want to survive and reproduce.

Similar organisms will be in the closet competition.

Populations of prey and predators go in cycles.

• The population of any species is usually limited by the amount of food available
• Prey increases > predator increases > prey decreases > predator decreases
• More grass > more rabbits > more foxes > less rabbits > less foxes.

Parasites and Mutalistic Relationships.

The survival of some organisms depends almost entirely on the presence of other species.

• Parasites live off a host. They take what they need to survive, without giving anything back. This often harms the host.
• Tapeworms absorb lots of nutrients from the host causing them to suffer malnutrition.

• Mutalism is a relationship where both organisms benefit
• Cleaner Species > Oxpeckers live on the backs of buffalo, they eat the pests on the buffalo (ticks, flies, maggots, providing the oxpecker with a source of food). They also alert the animal to any predators near by.

POLAR BEAR: -

• Thick hairy coat for keeping the body heat in
• White fut to match the surroundings for camouflage
• Big feet to spread the weight on snow and ice

CAMEL: -

• Thick coat that reflects sunlight in the day, to keep them cool, and keeps them warm at night when its cold
• Bushy eyelashes and hair-lined nostrils that can close to keep the sand out
• Large feet to spread load of soft land

CACTUS: -

• Small surface area to reduce water loss
• Store water in their thick stem
• Sharp spines to stop herbivores eating it.

Plants reproduce by transferring pollen to the stigmas of other plants of the same species.

Most use wind or insects to carry the pollen and they've adapted to whichever method they use.

WIND POLLINATION: -

• Long, feathery stigmas to provide a large surface area to trap pollen
• Pollen grains are light and dry which helps the wind carry them to the stigmas

INSECT POLLINATION: -

• Brightly coloured scented petals and scented nectar to attract insects.
• Their pollen grains are large and sticky, so that when an insect lands on the flower the pollen grains get stick to them.

Fossils are the remains of plants and animals

Fossils are evidence of organisms that lived a long time ago: -

• FROM GRADUAL REPLACEMENT BY MINERALS: teeth, shells, bones which don't decay easily can last a long time when buried. They're eventually replaced by minerals as they decay forming a rock like substance shaped like the original hard part. The surrounding sediments also turn to rock, but the fossil stays distinct inside the rock and eventually someone digs it up.
• FROM CASTS AND IMPRESSIONS
• FROM PRESERVATION IN PLACES WHERE NO DECAY HAPPENS

There are a few 'missing links' because the fossil record is incomplete. This is because very very few dead plants or animals fossilise and some body parts, like soft tissue and flesh, tend to decay away completely.

Charles Darwin... Only the fittest survive...

• Animals who have the most successful adaptations are the ones who are most likely to survive, reproduce and pass on their genes. This is the theory of natural selection.
• As environment change, certain adaptations will be better suited. If a variation gives organisms a survival advantage it is likely to become more common in the population.
• Over a long period of time, these evolved adaptations may even lead to a new species.

Modern Examples of Natural Selection: -

• Peppered moths adapted their colour
• Bacteria adapt to beat antibiotics
• Rats adapt to beat poison

Lamrack had a conflicting theory of evolution...

• If a characteristic is used a lot by an animal then it would become more developed.
• These acquired characteristics could be passed on to the animal's offspring.
• If a rabbit did a lot of running and developed big leg muscles, then the offspring would too

Human population is increasing.

The resources are being used up and more pollution's being produced.

This is causing Global Warming, Acid Rain and Ozone Depletion.

Fossil fuels are being burnt and releasing alot of carbon dioxide which causes global warming and sulphur dioxide which causes acid rain.

Indicator Species show pollution levels.

• Some species can only survive in unpolluted conditions so you know it is a clean area: Lichens are used to monitor air quality.
• Other species have adapted to live in polluted conditions so if there is a lot of them, it is a polluted area: Bloodworms, water-lice and rat-tailed maggots all indicate polluted water.

Endangered Species: -

• Destroying habitats: chopping down trees and making room for a rapidly increasing population means we're demolishing the homes of thousands of different species.
• Many animals are hunted for food, fur coats, jewellery or some just for fun.
• We're increasing the competition between species.

Protecting Endangered Species: -

• Education programmes
• Protected habitats
• Legal protection
• Captive breeding
• Creating artificial ecosystems

Conservation programmes: protect the human food supply, reduce the need for chemical pesticides, provided future medicines and help with cultural aspects. They don't just benefit the endangered species, they benefit humans too.

As the human population gets bigger we need to...

• Produce more food - more land for farming
• Find an alternative energy source
• Find a way to exist where we don't damage the environment

SUSTAINABLE DEVELOPMENT meets the needs of today's population without harming the ability of future generations to meet their own needs.

Examples of what's being done to promote sustainable development:

• Fishing quotas have been introduced to prevent some types of fish, such as cod, from becoming extinct in certain areas. This means they'll still be around in years to come.
• To make the production of wood and paper sustainable there are laws insisting that logging companies plant new trees to replace those that they've felled.

Education is important. If people are aware of the problems, they are more likely to help.

1. Whales have commercial value (they can be used to make money), dead or alive.

2. They're a tourist attraction

3.Whale meat and oil can be used and cosmetics can be made from a waxy substance in their intestines.

4.The International Whaling Commission has struggled to get nations to agree to restrict whaling. In 1982 the member nations declared a stop to whaling, the only exception being Norway, which still catches whales. Culling for scientific research is allowed in Japan, Iceland and the Faroe Isles.

5.It's hard to check that countries are sticking to the agreement, and a lot of illegal whaling goes on. Whale meat is regarded as a delicacy in some areas and it sells for very high prices.

6.Some whales are kept in captivity - there are different views about this:

• Whales don't have much space in captivity and they are sometimes used for entertaining people. People think they would be happier in the wild, but captive whales do increase the awareness of the animal's problems.
• Captive breeding programmes allow whales to be bred in numbers and released back into the wild.
• Research can help us understand their needs better to help conservation.