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Georgia Lofts

Georgia Lofts

Email: georgialofts@gmail.com

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About Me:I am a second year student studying BioMedical Science. I am interested in a wide range of topics but particularly like to focus on Biology, Art and Philosophy.

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GCSE Revision: Reproduction

GCSE Revision: Reproduction

GCSE BIOLOGY REVISION: REPRODUCTION

Please note: Text in bold is what the AQA GCSE biology specification requires an understanding of.

Students should understand that meiosis leads to non-identical cells being formed while mitosis leads to identical cells being formed.

 

What is meiosis?

A type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

 

What is mitosis?

A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.

 

Mitosis division results in two identical daughter cells whilst meiosis results in 4 non-identical sex cells.

 

There are some similarities between the two types of division, but it is very important to know the differences. Do not get them mixed up!

 

 Sexual reproduction involves the joining (fusion) of male and female gametes:

sperm and egg cells in animals

 pollen and egg cells in flowering plants.

 

Terminology

Gametes-  are a mature haploid male or female germ cell which is able to unite with another of the opposite sex in sexual reproduction.

Germ cell- a cell containing half the number of chromosomes of a somatic cell and able to unite with one from the opposite sex to form a new individual; a gamete.

Fertilisation- a process in sexual reproduction that involves the union of male (sperm) and female (ovum) gametes (each with a single, haploid set of chromosomes) to produce a diploid zygote.

Haploid- having a single set of unpaired chromosomes

Diploid- containing two complete sets of chromosomes, one from each parent

 

Sexual reproduction requires two parents. The nuclei of male and female gametes fuse together to form a zygote (fertilisation.) Each gamete is haploid. In order to create a human embryo, gametes must join to get a full set of chromosomes.

 

The gametes in:

Animals are sperm (male) and eggs (female)

Flowering plants are pollen (male) and eggs (female)

 

In sexual reproduction, there is mixing of genetic information which leads

to variety in the offspring. The formation of gametes involves meiosis.

 

As there is genetic mixing, this means that offspring produced by sexual reproduction are genetically different to the parents and each other (variation).

 

Features of sexual reproduction using meiosis

Making genetic information copies

The cell divides twice to form four gametes (each has a single set of chromosomes)

Each gamete is different

 

In humans, the two number of chromosomes the body requires is 46. 23 chromosomes= haploid.

______________                 ________________           ___________________

(23 chromosomes) +      (23 chromosomes )         =        (  46 chromosomes    )

______________                 ________________            ___________________

 

sperm cell                                egg cell                                           diploid zygote

 

 

A zygote will mature into an embryo. The number of cells increase by mitosis. As the embryo develops, cells will begin to differentiate/ specialise.

 

Differentiate- make or become different in the process of growth or development

Specialise- become adapted to a special function in a particular environment.

 

 

Image- http://igbiologyy.blogspot.com/2014/04/148-summary-of-reproduction.html

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