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B1 (3) (Environmental Change (Causes of Change (Non-Living(include global…
B1 (3)
Environmental Change
Causes of Change
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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
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In recent year, honeybees numbers are declining(don't know the cause)
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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)
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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
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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
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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
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Crabs, worms and fish eat the whale body
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Genes and Chromosomes
Chromosomes numbers
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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)
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Genetic Engineering
How
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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
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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