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biology - Coggle Diagram
biology
cell division
Chromosomes and DNA
A type of cell division called mitosis ensures that when a cell divides each new cell produced has the same genetic information
DNA exists in a cell's nucleus within structures called chromosomes. Each section of a chromosome that contains the code for the production of a particular protein is called a gene
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.In females, the two chromosomes are identical in shape. There are two X chromosomes. Females are referred to as XX.
.In males, one of the chromosomes is a difference in shape. There is an X and also a Y chromosome. Males are referred to as XY
Stem cells
Stem cells are cells that have not undergone differentiation. A cell which has not yet become specialised is called undifferentiated
An embryo develops from a fertilised egg. Cells at the early stages in the development of the embryo are stem cells
Adult stem cells can be found in the brain, eyes, blood, heart, liver, bone marrow, skin and muscle. Adult stem cells can differentiate into related cell types.
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stem cells in plants
cell divition in plants occors in regions called meristems. Cells of the meristem can differentiate to produce all types of plant cells at any time during the life of the plant.
The main meistems are close to the tip of the shoot, and the tip of the root
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Cell differentiation
Animals and plants produced by sexual reproduction begain life as a single cell– A ertilised egg or zygote.
Cells must divide to produce a multicellular organism. It must also differentiate so the cells develop features
Using human stem cells
Stem cells can divide to produce new cells, which can divide into different cell types. This means they can be used to treat
medical conditions. They can also be used to replace cells that have been destroyed or damaged
Embryonic stem cells can differentiate into a wider range of cell types, but are difficult to obtain and their uses rais ethical challenges
Adult stem cells will differentiate into a narrower range of cell types. Bone marrow transplants are an example of adult stem cell transplant.
Communicable diseases
Pathogens
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These include viruses, bacteria, fungi and protists
All types of pathogen have a simple life cycle. They infect a host, reproduce themselves or replicate if it is a virus, spread from their host and infect other organisms.
Diseases caused by pathogens are called communicable diseases. This means they can be transferred from one person to another.
Viral diseases
Viruses are not alive because they do not complete all of the seven life processes: Movement, Respiration, Sensitivity, Nutrition, Excretion, Reproduction and Growth
The life cycle of a virus is the same as other pathogens. They can often survive outside a host for long periods of time. When they have infected a suitable host cell or cells, they replicate themselves within the cell thousands of times
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Bacterial diseases
Not all bacteria are pathogens which cause disease. Many bacteria, like those found in the intestines, are useful. All bacteria are prokaryotes, and do not have a nucleus
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photosynthesis
what is photosynthesis
Photosynthesis is where plants make their own food unlike animals. During photosynthesis, plants produce glucose from simple inorganic molecules-carbon dioxide and water-using light energy
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plants leaves are the main organ but any part of the plant can develop chlorophyll and photosynthesise
The light energy required is absorbed by a green pigment called chlorophyll in the leaves. Chlorophyll is located in chloroplasts in plant cells, particularly the palisade and spongy mesophyll cells
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Required practical
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steps
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sodium hydrogencarbonate – formula NaHCO3 – is added to the water to supply carbon dioxide – a reactant in photosynthesis – to the plant
the light intensity is proportional to distance – it will decrease as the distance away from the bulb increases – so light intensity for the investigation can be varied by changing the distance from the lamp to the plant
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Animal tissues, organs and organ systems
Cells, tissues and organs
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Specialised cells
They have structures that are adapted for their function. They contain protein fibres that can contract making them shorter
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