genetics and carbon cycle

Question	Answer
Explain the role of the Sun in food chains on Earth	Radiation from the Sun is the source of energy for most communities of living organisms. Green plants and algae absorb a small amount of the light that reaches them. The transfer from light energy to chemical energy occurs during photosynthesis. Energy is stored in the substances that make up plant cells.
What is biomass and how does it change with each new stage in a food chain ?	The mass of living material (biomass) at each stage in a food chain is less than it was at the previous stage.
The amounts of material and energy contained in the biomass of organisms are reduced at each successive stage in a food chain . Explain how.	■ lost in the organisms’ waste materials ■ respiration, loss of carbon dioxide ■ not all organisms are eaten by the higher level
Why do materials decay and what can increase the rate of decay ?	Materials decay because they are broken down (digested) by microorganisms. Microorganisms are more active and digest materials faster in warm, moist, aerobic conditions.
Why is the decay process important ?	The decay process releases substances that plants need to grow.
Describe the carbon cycle	1. photosynthesis takes carbon dioxide in 2. combustion releases carbon dioxide from fuels and wood 3. respiration releases carbon dioxide from plants, animals, detritus feeders and microorganisms
what are detritus feeders	detritus feeders are animals that eat dead and decaying material eg earthworms
what are chromosomes and where are they found	The nucleus of a cell contains chromosomes. Chromosomes carry genes that control the characteristics of the body.
What do genes do ?	Different genes control the development of different characteristics of an organism.
Differences in the characteristics of different individuals of the same kind may be due to differences in what ?	■ the genes they have inherited (genetic causes) ■ the conditions in which they have developed (environmental causes) ■ or a combination of both.
Describe sexual reproduction	■ sexual reproduction – the joining (fusion) of male and female gametes. The mixture of the genetic information from two parents leads to variety in the offspring
Describe asexual reproduction	■ asexual reproduction – no fusion of gametes and only one individual is needed as the parent. There is no mixing of genetic information and so no genetic variation in the offspring. These genetically identical individuals are known as clones.
compare cloning a plans by cuttings and tissue culture	taking cuttings is cheap and effective using tissue culture is more expensive requires special equipment but can produce large numbers of plants. it is good if you want to clone a rare plant
Describe how to clone and animal using embryos	embryo transplants – splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers
Describe adult cell cloning	adult cell cloning – the nucleus is removed from an unfertilised egg cell. The nucleus from an adult body cell, eg a skin cell, is then inserted into the egg cell. An electric shock then causes the egg cell to begin to divide to form embryo cells. These embryo cells contain the same genetic information as the adult skin cell. When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development.
describe how to genetically alter an organism	In genetic engineering, genes from the chromosomes of humans and other organisms can be ‘cut out’ using enzymes and transferred to cells of other organisms.
give examples of genetically modified organisms	examples of genetically modified crops include ones that are resistant to insect attack or to herbicides
Give a benefit of genetically modified crops	genetically modified crops generally show increased yields.
what concerns are there about gm crops	Concerns about GM crops include the effect on populations of wild flowers and insects, and uncertainty about the effects of eating GM crops on human health.
what is a gene ?	part of a chromosome that controls a characteristic
what is carbon from the carbon cycle used to make	the carbon from the carbon dioxide is used to make carbohydrates, fats and proteins, which make up the body of plants and algae
why is it more difficult to successfully clone animals than plants	Animal embryos must be split into groups of cells and then each group is transplanted into a host mother. there have to be enough hosts and some embryos may die during development. it also takes longer for the animals to develop
list the benefits and disadvantages of adult cell cloning	benefits 1. many uses in medicine 2. produce valuable proteins in milk 3. can save animals from extinction disadvantages 1. concerns about ethics of cloning 2. cloning reduces the gene pool, can be a problem for natural selection if the environment changes 3. ethical concerns about using the technique to clone humans - many failed attempts
what are the benefits of genetically engineering animals	1. cloning cattle can produce herds of cattle with useful characteristics 2. adult cell cloning may be used to make copies of the best animals eg race horses 3. if a person has a faulty gene they may have a genetic disorder. if the correct gene can be transferred to the person they could be cured
why should you genetically engineer animals (insert a gene ) at an early stage of development	so that the new gene will end up in all the cells of the body when the cells divide
what is meant by the host animal	the host animal is the one in which a transplanted embryo develops
why does a compost heap get hot	heat produced by respiration by decomposers
why do we normally eat herbivores rather than carnivores	there are less stages in the food chain. eating plants is the most efficient way of feeding the world population but if we want meat less energy is wasted if we eat herbivores

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