B1 (3)

Environmental Change

Causes of Change

Non-Living(include global warming such as rain in the centre of Australia)

Living(include the introduction of the grey squirrel into Britain which caused a decrease in the population of the native red squirrel)

The Disappering Bees

Honeybees help pollinate flowers that will develop into food crops

In recent year, honeybees numbers are declining(don't know the cause)

Pollution Indicators

Measuring Changes in the Environment

In the UK, the composition of the air o=and of the water in rivers and streams; and the air temperature and rainfall, are constantly being measured. This makes sure that any changes can be tracked

Oxygen meters measure the concentration of dissolved oxygen in the water. Unpolluted water will contain a lot of dissolved oxygen

Thermometers measure temperature. Rain gauges measure rainfall

Living organisms can find out pollution levels

Lots of sulfur dioxide in the air, many species of lichens will not be able to grow

Not much oxygen in the river, there will be no oxygen-loving mayfly larvae in the water, instead there will just be rat tailed maggots and bloodworms

Sewage Pollution and Invertebrates

Very Polluted(Blood worm, Chironomid larva, Rat tailed maggots

Polluted(Mosquito larva, Tubifex worm)

Slightly Polluted(Flateworm, Caddis larva)

Unpolluted(Freshwater shrimp, Mayfly larva, Stonefly larva)

Food Chains and Energy Flow

Energy Wasting

Green plants only capture small amount of energy from the light that falls onto them

Because some light misses them all together, hits the leaf and reflects back, hits the leaf but goes all the way through without hitting any chlorophyll, hits the chlorophyll but is not absorbed because it's the wrong wavelength(colour)

As a result, very little pf the light energy is used for photosynthesis ad get transferred into chemical energy in carbohydrates and other substances

Efficiency

Whenever energy is transferred, some is wasted

efficiency = useful energy transferred x 100 / original amount of energy

Biomass

Energy Loss

Energy is lost as the food chain progresses as for each step, there is less energy available for the organisms to use(less energy = less biomass)

Reasons for Losing Energy

Waste materials(CO2, urine and faeces)

Respiration(lost heat to surroundings)

Not all tissue in organisms is eaten

More about Energy Loss

Mammals and birds use glucose to provide energy to keep their body temperature high(energy loss in birds and mammals is high)

Snakes, frogs and fish stay at the same temperature as their environment

Decay

Speeding and Slowing Decay

Bacteria and Fungi that carry out decay need

Oxygen for aerobic respiration

A warm temperature for their enzymes to work at an optimum rate

Moisture for reproduction

Increasing temperature on an organisms slows or stops decay

Preventing decay

If food is not to decay, it can be treated so as to slow down or stop the activity of micoorganisms

Examples of this include canning, pickling and drying food

Recycling

Recycling and Food Chain

Decay organisms feed on every organism in the food chain

They will break down most of the waste material that the plants and animals produce, and then their bodies will be broken down by others when they die

Dead Whales

Whole communities of organisms use whale carcasses as food

Crabs, worms and fish eat the whale body

Microorganisma gradually decay the whales tissues. The whole process can take decades

Carbon Cycle

Processes in the Carbon Cycle

Photosynthesis converts carbon dioxide into carbohydrates and other food molecules such as protein(carbon dioxide + water -> glucose +oxygen)

When animals eat plants (or other animals) the food goes into their cells and is broken down by respiration(glucose + oxygen -> carbon dioxide + water)

C02 is returned to the air when animals breathe out and when fossil fuels are burnt(combustion), Plants and microorganisms also respire, Some dead organisms do not decay(buried and compressed and change into fossil fuels),

Energy in the carbon cycle

During photosynthesis, energy from sunlight is transferred to energy stores as chemicals in carbohydrates

Some of this energy is transferred to other organisms(such as animals and decomposers when they feed on animals)

Some energy is wasted, heating the soil and air

Genes and Chromosomes

Chromosomes numbers

Chromosomes are long sections of DNA

Most human cells have 46 chromosomes, that is 23 from the gamete of each parent(egg and sperm), which carry about 2500 genes

Each gene contains coded information that controls one characteristic. For example, some genes control hair colour. Other genes control eye colour

Most of these genes come in two or more forms. For example, a gene that controls hair colour might have one form that produces brown hair and a different that forms red hair

Causes of Variation

Variation(differences) in organisms may be due to either- the genes they have inherited(genetic cause) or the condition in which they have developed (environmental cause)

Reproduction

How it Works

In sexual reproduction, gametes and fertilisation are always involved

The new cell that is produced by fertilisation is zygote(divides to produce a little ball of cells which develops into an embryo)

Produces a variety in the offspring because each zygote has a different mix of genes from its parents and its brothers and sisters

In asexual reproduction, an individual splits in twos (as in bacteria) or divides a part off(this is the offspring)

There's no variation, all the organisms all have exactly the same genes as their parent(genetically identically)

Different Fertilisation

In birds and animals, the male sperm are deposited and the egg is fertilised inside the female's body(internal fertilisation)

Male fish and female fish shed sperm and eggs into water(external fertilisation))

Cloning Plants and Animals

Cloning Methods

Cuttings

A way of making new plants from one original plant

Stems are cut from the parent plant and dipped in hormone rooting powder and then placed in soil

The cuttings will grow into new plants which are genetically identical to each other and the parent plant

Tissue Culture

A small piece of tissue is taken from a root, stem or leaf of the parent. The tissue is then grown on a jelly containing all nutrients it needs

Everything has to be kept sterile, so this is usually done in a lab

Eventually, each tiny group of cells grows into a complete adult plant cell

Embryo Transplant(animals)

Egg cells are taken from a cow and fertilised with sperm from a bull

One embryo is chosen and spilt into two(or more) and then each placed into a host mother

The calves born are clones of each other as they have the same genes

Adult-Cell Cloning

1- The nucleus is removed from an unfertilised egg cell

2- A nucleus is taken from another cell in an adult animals's body

3- This nucleus is put into the egg cell

4- The egg cell is given a small electric shock. This persuades it to start dividing

5- The egg cells grows into an embryo. Each of its cells contains exactly the same genes as the adult cell which the nucleus was taken

6- When the embryo is big enough, it is put into a uterus of a host mother. top continue its development

Genetic Engineering

How

Bacteria have been genetically engineered to make human insulin

Farmers spray bean fields with herbicides to kill weeds that compete with soya plants(contains glyphosate)

Some soya bean varieties have been genetically engineered to give them a gene that make them resistant to glyphosate(weed dies, beans don't)

Genetic Modification

Some GM crops are resistant to pests. This increase the yields and prices are kept down. Also reduces the amount of pesticide that has to be sprayed

Concerns

Genes for a toxin to kill insects could be transferred to wild plants, which could disrupt the food chain

There may be effect on humans of eating food from GM plants

Have to thoroughly tested before they are allowed to be grown on a large scale there is no evidence that eating GM plant does any harm