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Science form 3 chapter 4 asexual reproduction in bacteria

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Sexual reproduction involves the fusion Science form 3 chapter 4 asexual reproduction in bacteria male and female gametes to form a zygote. The fusion of the nuclei of male and female gametes is known as fertilization. Asexual reproduction does not involve gametes, instead parts of a mature organism may develop to new individuals. Cell division starts with division of nucleus i. In unicellular organisms the cell divides into two separate daughter cells while in multicellular ones the cell divides into two and continues to divide in the same way.

There are two types of cell division namely mitosis and meiosis. The term interphase is used to describe the state of the nucleus when the cell is just about to divide. Introduction The process by which mature individuals produce offspring. Reproduction is an essential characteristic of all living organisms.

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There are two types of reproduction: Importance of reproduction Procreation - reproduction sustains the species so that it does not become extinct. Quality improvement- it allows for the mixing of genetic materials leading to variation among individuals in a species. This is seen in sexual reproduction.

PMR Form 3 Science Chapter...

The variations form basis of adaptability in their Science form 3 chapter 4 asexual reproduction in bacteria. Chromosomes In the nucleus are a number of thread-like structures called chromosomes. Each cell has fixed number of chromosomes.

Each chromosome is made up of two parallel strands called chromatids each pair of chromatid is connected atone point by a structure called centromere. Chromosomes are present in the nucleus all the time, but only become visible when viewed under a microscope during cell division. Chromosomes occur in pairs in the body cells and each pair has a characteristic length. The member of each pair is called a homologous chromosome. This means that they look alike in appearance although their genetic composition may be different.

Along the length of the chromosomes is a series of structures called genes. They are too small to be seen even under a powerful microscope. Genes determine the characteristics of the cell and its progeny. Genes are made up of a protein chemical substance called DNA Deoxyribonucleic acid which contain coded information of instructions that dictate the characteristics of the offspring. The sequence of events leading to cell division in plants and animals is basically the same. This is a type of cell division in which a cell divides into two daughter cells each having the same numberof chromosomes as the parent cell.

This takes place in all body somatic cells of an organism to bring about increase in number of cells, resulting in growth and Science form 3 chapter 4 asexual reproduction in bacteria. Mitosis is usually described as a series of stages for convenience of explaining the process involvrd in a logical manner.

These stages of cell division occur in a smooth and continuous pattern so that one stage merges with the next without interfering with the activities of the cell. Interphase The term interphase is used to describe the state of the nucleus when the cell is just about to divide. During this time the following take place: Multiplication of genetic material so that daughter cells Science form 3 chapter 4 asexual reproduction in bacteria have the same number of chromosomes as the parent cell.

Manufacture of cell organelles such as mitochondria, golgi bodies, centrioles, ribosomes and centrioles. Energy for cell division is synthesised and stored in form of Adenosine Triphosphate ATP to drive the cell through the entire process. During interphase, the following observations can be made: Chromosomes are seen as long, thin, coiled thread-like structures.

Nuclear membrane and nucleolus are intact. Prophase The chromosomes shorten and thicken. Each chromosome is seen to consist of a pair of chromatids joined at a point called centromere. Centrioles in animal cells separate and move to opposite poles of the cell. The centre of the nucleus is referred to as the equator. Spindle fibres begin to form, and connect the centriole pairs to the opposite poles. The nucleolus and nuclear membrane disintegrate and disappear.

Metaphase The nuclear membrane disappears hence chromosomes are free in the cytoplasm. The spindle fibres lengthen. In animal cells they attach to the centrioles at both pole Each chromosome moves to the equatorial plane and is attached to the spindle fibres by the centromeres.

Anaphase The following events occur during this phase, Chromatids separate and migrate to the opposite poles due to the shortening of spindle Science form 3 chapter 4 asexual reproduction in bacteria. In animal cells, the cell membrane starts to constrict towards the end of the anaphase.

Telophase This is the final phase ofcell division The chromatids collect together at the two opposite ends of the spindle. A nuclear membrane forms around each set of chromatids andare nowreferred to as chromosomes.

Form 3 PMR Science Chapter...

The cytoplasm divides into two leading to the formation of two daughter cells. Chromosomes later become less distinct.

FORM 3 SCIENCE. CHAPTER 4...

Significance of Mitosis It brings about the growth of an organism: It is a basis of asexual reproduction. Ensures that the chromosome number is retained.

Ensures that the chromosomal constitution of the offspring is the same as the parents. Important genetic changes usually result.

FORM 3 SCIENCE CHAPTER 4...

What is asexual reproduction? In flowering plants, a flower is the reproductive organ which is a specialised shoot consisting of modified stem and leaves. Regular flower Those that can be divided into two similar halves by any vertical section passing through the centre. Irregular flower Can be divided into two equal halves in one particular plane only. Pedicillate flower Flower with a stalk.

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Solitary flower Those that occur singly while those that grow in cluster make an inflorescence. How is a fruit formed? What is seed and fruit dispersal? There are two types of fertilisation. Fertilisation in mammals occurs internally. After fertilisation the fertilised egg is laid or develops within the female body in a special structure, the uterus.

An example of an oviparous mammal is the platypus. In some mammals, the zygote does not develop fully within the uterus but completes development within a special structure called pouch as in the marsupials eg kangaroo.

In most mammals however, the zygote develops fully into a young mammal which resembles that adult. The ability to give birth to young as in placental mammals is referred to as Viviparity. The glands produce milk on which the young ones feed on until they are able to feed on the same food as adults. In these mammals, parental care is highly developed. Reproduction in Human Beings Science form 3 chapter 4 asexual reproduction in bacteria of female reproduction system The female reproduction system consists of the following: Week 1 to 3: Week 4 to 7: Week 8 to H causes the mature ovum to be released from the Graafian follicle - a process called ovulation.

H which causes the Graafian follicle to develop in the ovary. Nandi flame, Jacaranda Sonchus, cotton seed, Tecoma. Causes ovulation; causes development of Graafian follicle into the corpus luteurn; causes secretion of progesterone by the ovary. Causes changes in the uterine wall in preparation for implantation; initiates development of secondary sexual characteristics. A void indiscriminate sex. Treat both partners infected A void sharing linen.

Solitary painless ulcer-on genital or mucous -Rashes, muscles and papules on hands, feet lips, genital areas. Treat at primary infection stage -Avoid indiscriminate Sex. Lesions on skin and mucous membranes of buccal cavity vagina or head of penis. Revise how sexual reproduction produces offspring that are not identical to their parents, whereas asexual reproduction produces identical offspring.

Test. 1; 2 · 3 · 4 · 5 · 6 · 7; Page 1 of 7 Only one parent is needed in asexual reproduction, and the offspring produced are genetically identical, eg reproduction in bacteria. Form 3 PMR Science Chapter 4 Plant Reproduction. Plant Asexual Reproduction Above ground Stems arch over and take. (2) Disease Science form 3 chapter 4 asexual reproduction in bacteria There are many diseases - includingfungi, viruses and bacteria - that can. FORM Science form 3 chapter 4 asexual reproduction in bacteria SCIENCE CHAPTER 4 REPRODUCTION 1.

Reproduction Sexual Asexual - Involving fusion of male and female i. fission – split into two ↓ ↓ - such as amoeba, paramecium, euglena, Sperm Ovum chlamydomonas and bacteria.

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