B5 - Growth and Development

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Cambridge IGCSE Biology Flashcards on B5 - Growth and Development, created by franimal on 13/11/2013.

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Question Answer
"Every kind of cell in the human body is specialised" - explain. Different types of cells do different jobs and they can only do that particular job.
What are groups of one cell type called? Tissues
What is the main difference between an animal and a plant cell? Plant cells have cell walls.
What is a fertilised egg called? A zygote.
How does an embryo divide? Using mitosis.
What are embryonic stems cells? The cells in the early embryo that can develop into whole individuals because they're unspecialised.
What are the dividing cells that cause the plant to widen called? Meristem cells.
Why do meristems work? Meristem cells are unspecialised so can develop into anything.
What stem cells do adult humans have? Skin cells and blood cells from the bone marrow.
What is rooting powder and what is the active ingredient? Auxin - it causes new cells at the base of the stem to develop into roots, and so is used in cuttings.
Why do gardeners use cuttings? Quick, cheap and produces exactly the same features as the parent plant.
What is phototropism? The bending of growing plant shoots towards the light.
How does phototropism occur? Auxin is a plant hormone that causes cells to expand. It diffuses away from light and makes the shaded area bend towards the light.
How was phototropism proved to be only in the tips? Darwin put caps that blocked light on different areas of the plant. When the tips were covered, the plant remained upright.
What is a chromosome? A long molecule of DNA wound around a protein framework.
What is the first stage of mitosis? The chromosome develops an identical copy attached to itself and the membrane around the nucleus breaks down.
What happens at the second stage of mitosis? The chromosomes uncoil and are dragged into the middle by protein fibres.
Describe stage 3 of mitosis. The chromosomes are pulled apart by the protein fibres to opposite ends of the cell.
What is the last stage in mitosis? New nuclear membranes form and chromosomes recoil. The cell then divides.
What is a gamete? Sex cells.
What is meiosis? The type of division that splits a normal cell into four sex cells, each with half the amount of chromosomes of the parent.
What was Watson and Crick's major discovery? That DNA had a double helix structure.
What is base pairing? The bases of a DNA molecule always bond in the same way, A with T, G with C.
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