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