B3d: Cell Division

As living things grow, the number of cells in them increases. This brings significant advantages, and requires the development of complex organ systems. This item looks at the two ways cells divide, mitosis and meiosis, and the differences between these types of cell division. Software simulations and video clips which show cell division are uses of ICT in teaching and learning. 

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What type of organism may be unicellular? Simple or Complex? What does this mean?
Simple, consisting of just one cell.
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What type of organism may be multicellular? Simple or Complex? What does this mean?
Complex, consisting of more than one cell
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What do most body cells contain.
Chromosomes in matching pairs.
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Explain why the chromosomes have to be copied to produce new cells for growth.
So that each new cell still has the full amount of DNA. If DNA didn't replicate itself then there wouldn't be enough DNA in the new cell
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Recall three things mitosis is used for.
Replacement of worn out cells, repair to damaged tissues and asexual reproduction.
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Why are sperm cells produced in large numbers?
To increase the chance of fertilisation.
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What has to happen in asexual reproduction to produce a unique individual?
Half the genes come from each parent.
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Do gametes have the same number of chromosomes as body cells?
No, they have half.
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When does sexual reproduction happen? What is this process called?
When a male gamete and a female gamete join. This process is called fertilisation.
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What are the three advantages of being multicellular?
Allows organism to be larger, allows for cell differentiation and allows organism to be more complex.
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What specialised organ system does a multicellular organism need and why?
Nervous system - to allow communication between cells, Circulatory system - to supply all with cells with nutrients, and a respiratory system - to control the exchange of substances with the environment
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How are new cells for growth produced?
By mitosis.
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Why are new cells produced by mitosis identical?
Because the DNA in the cell must be copied (replicated) before the cell divides into two.
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In mammals, are body cells haploid or diploid?
Diploid.
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What is he definition of diploid?
(two copies of each chromosome)
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Explain the process of DNA replication.
The DNA 'unzips' to form single strands, free nucleotides lock on to bases, new double strands forming by complementary base pairing.
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Describe the process of mitosis.
DNa replicates, chromosomes line up at centre of cell, divide, the copies move to opposite poles of the cell. Cell divides into two.
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By what process are gametes produced?
Meiosis
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Are gametes haploid or diploid?
Haploid
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What is the meaning of haploid?
Contain one chromosome from each pair
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Why does fertilisation result in genetic variation?(2)
Gametes combine to form a diploid zygote and genes on the chromosomes combine to control the characteristics of the zygote.
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Why do sperm cells have many mitochondria?
to provide energy.
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What does a sperm's acrosome do?
releases enzymes to digest the egg membrane.
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Describe the process of meiosis.
DNA replicates, similar chromosomes pair up, sections of DNA get swapped, pairs of chromosomes divide, chromosomes divide.
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Explain why, in meiosis, the chromosome number is halved and each cell is genetically different.
In the first division, one chromosome from each pair separate to opposite poles. In the second division, the chromosomes divide and the copies move to opposite poles.
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Card 2

Front

What type of organism may be multicellular? Simple or Complex? What does this mean?

Back

Complex, consisting of more than one cell

Card 3

Front

What do most body cells contain.

Back

Preview of the front of card 3

Card 4

Front

Explain why the chromosomes have to be copied to produce new cells for growth.

Back

Preview of the front of card 4

Card 5

Front

Recall three things mitosis is used for.

Back

Preview of the front of card 5
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