Life started as a single cell - a fertilized egg cell. cell divide to make two cells, these divide to make four, and so on. This is called cell division. It is how all living things grow.

A fertilized egg cell divides to make two daughter cells, which are identical.

These divide to make four identical cells, which divide again and again to make a ball cell

Cell division by Cell division by MitosisMitosis

Mitosis is the process of cell growthMitosis is the process of cell growth Happens in body cellsHappens in body cells LLife starts as a fertilized egg cell, smaller than a full stop. This cell divided millions of times by a process called

mitosis, to produce all the cells which make up your body. 2 N (diploid) cells produce more 2 N cells Daughter cells same as parent After fertilization cells divide by mitosis Not all cells divide at the same rate Stem cells in bone marrow male red blood cells (RBC)

everyday Nerve and muscle cells lose the ability to divide

How the cell divides by mitosis : How the cell divides by mitosis : When a cell is ready to divide, When a cell is ready to divide,

long, thin double threads called long, thin double threads called chromosomes appear in its chromosomes appear in its nucleus (A). In this cell only two nucleus (A). In this cell only two chromosomes are show, chromosomes are show, (human cells have 46 (human cells have 46 chromosomes altogether). chromosomes altogether). Chromosomes contain Chromosomes contain chemicals which control what a chemicals which control what a cell does. These chemicals cell does. These chemicals also contain all the instructions also contain all the instructions needed to build a whole new needed to build a whole new organism from a single organism from a single fertilized egg cell.fertilized egg cell.

Next these double chromosomes become shorter and thicker Next these double chromosomes become shorter and thicker and move to the middle (equator) of the cell, where they and move to the middle (equator) of the cell, where they become attached to fin, fibres called the spindle (B).become attached to fin, fibres called the spindle (B).

Spindle fiberSpindle fiber

Each chromosome then separates into two parts which move Each chromosome then separates into two parts which move to opposite ends of the cell (c). The two halves am probably to opposite ends of the cell (c). The two halves am probably pulled apart by the spindle threads.pulled apart by the spindle threads.

The cell then divides, separating the two groups of chromosomes, which form a nucleus in each daughter cell (D).

Overall view of MitosisOverall view of Mitosis

The two daughter cells have exactly the same number of chromosomes as the parent cell, and their chromosomes are exact copies of those in the parent cell.

In scientific terms they are said to be genetically identical to the parent cell.

A cell dividing by mitosis. The deep pink parts are the chromosomes.

There are two ways in which living things can reproduce; by There are two ways in which living things can reproduce; by asexual reproductionasexual reproduction or or sexual reproductionsexual reproduction. In asexual . In asexual reproduction there is only one parent, and its young are exact reproduction there is only one parent, and its young are exact copies of itself because they have been produced by mitosis. copies of itself because they have been produced by mitosis. Single celled creatures, like Amoeba, reproduce asexually by Single celled creatures, like Amoeba, reproduce asexually by mitosis to form a genetically identical group called a clone.mitosis to form a genetically identical group called a clone.

Asexual reproduction in plants is called Asexual reproduction in plants is called vegetative reproductionvegetative reproduction. . Plants grow parts by mitosis which break off to become separate Plants grow parts by mitosis which break off to become separate plants. Strawberry runner are an example. They grow buds which plants. Strawberry runner are an example. They grow buds which form new plants, and the runners die away.form new plants, and the runners die away.

Cell division by meiosisCell division by meiosis Meiosis is the cell division of sex cellsMeiosis is the cell division of sex cells To reproduce sexually organisms must produce sex To reproduce sexually organisms must produce sex

cells called gametes. Male animals have gametes cells called gametes. Male animals have gametes called sperms, made in the testes. Female animals called sperms, made in the testes. Female animals produce ova (one is an ovum) or eggs, from ovaries. produce ova (one is an ovum) or eggs, from ovaries. Flowering plant male gametes are pollen grains Flowering plant male gametes are pollen grains made in anthers. Plant female gametes are ovules made in anthers. Plant female gametes are ovules made in ovaries.made in ovaries.

Gametes are produced by a kind of cell division Gametes are produced by a kind of cell division called meiosis. Male and female gametes fuse called meiosis. Male and female gametes fuse together during sexual reproduction to make a together during sexual reproduction to make a fertilized ovum, called a zygote. This divides millions fertilized ovum, called a zygote. This divides millions of times by mitosis as it grows into an adult.of times by mitosis as it grows into an adult.

Overview of MeiosisOverview of Meiosis

Cell division by meiosisCell division by meiosis

The cells in your body contain 46 chromosomes The cells in your body contain 46 chromosomes but if human gametes had this number, when but if human gametes had this number, when they fused together the zygote would have 92, they fused together the zygote would have 92, and this number would double at each and this number would double at each generation. This does not happen because generation. This does not happen because meiosis makes gametes with only 23 meiosis makes gametes with only 23 chromosomes, and fertilization makes a zygote chromosomes, and fertilization makes a zygote with 46.with 46.

As meiosis starts chromosomes become shorter As meiosis starts chromosomes become shorter and thicker and are seen as double threads, and thicker and are seen as double threads, having just made exact copies of themselves. having just made exact copies of themselves.

They form into pairs (A), the They form into pairs (A), the members of which are about members of which are about the same and shape. One the same and shape. One member of each pair is a member of each pair is a descendant of one of the 23 descendant of one of the 23 chromosomes in the mother's chromosomes in the mother's ovum, and the other descends ovum, and the other descends from one of the 23 from one of the 23 chromosomes in the father's chromosomes in the father's sperm.sperm.

The pairs gather around the equator of the cell The pairs gather around the equator of the cell attached to the spindle apparatus (B).attached to the spindle apparatus (B).

Spindle fibreSpindle fibre

The members of each The members of each parts then separate and parts then separate and move in opposite directions move in opposite directions (c).(c).

followed by each followed by each chromosome splitting into chromosome splitting into two (D).two (D).

The cell divides into The cell divides into four new cells (E) four new cells (E) with only half the with only half the number of number of chromosomes or chromosomes or the parent cell.the parent cell.

Meiosis, mitosis, and reproductionMeiosis, mitosis, and reproduction

Meiosis errors only in the reproductive organs (testes, anthers and ovaries) to produce gametes.

Mitosis produces new body cells for growth, and to replace damaged tissues.

The gametes which meiosis produces have only half the number of chromosomes of body cells, because they have only a single set of chromosomes.

In humans this is 23, which is known as the haploid number of chromosomes.

Fertilization restores the full (double) set of chromosomes which, in humans, is 46, and this is called the diploid number.

Mitosis produces cells with the same (usually diploid) number of chromosome.

In humans … At fertilization, 23 chromosomes are donated

by each parent. (total = 46 or 23 pairs).

Gametes (sperm/ova): Contain 22 autosomes and 1 sex chromosome. Are haploid (haploid number “n” = 23 in humans).

Fertilization results in diploid zygote. Diploid cell; 2n = 46. (n = 23 in humans)

Most cells in the body are produced by _________.

Only gametes are produced by _________.

2n

Clone

Same genetic information in parent cell and daughter cell.

Give me another one just like the other one!

1n

Daughter cells different from parent cell and from each other.

Daughter cells have ½ the number of chromosomes as somatic cell.

Shuffling the genes(Mix it up!)

Mitosis vs. Meiosis