This document provides an overview of sexual and asexual reproduction in plants and animals. It discusses the process of cell division through mitosis, which results in two daughter cells that are identical to the parent cell. The four phases of mitosis - prophase, metaphase, anaphase and telophase - are described in detail. The stages of interphase and how the cell prepares for division are also outlined. The roles of chromosomes, genes, and other cellular structures in heredity and cell division are explained.

1. Secondary Biology,
Reproduction in Plants and
Animals
Cell division; Mitosis
By Mr. Kanyoro Peter

2. Introduction
 Reproduction is the process by which mature
living organisms produce young ones of their
kind/offspring.
 It’s of two types;
 Sexual reproduction – involves fusion of sex cells
(male and female gametes) in a process called
fertilization.
 Asexual reproduction – where parts of mature
organisms develop into new individuals in several
mechanisms.

3. Sexual (a) and Asexual (b)
reproduction

4. Importance of reproduction
 Leads to procreation hence
perpetuation/survival/sustenance of
species so that it dose not become
extinct
 Helps in improvement of quality of
species through exchange of genetic
material during crossing over hence
variation and adaptability.
 Helps to maintain all the
characteristics of the parent as in
asexual reproduction.

5. Cell division
 Organisms start as a single cell; spore or
zygote
 Cells of multicellular organisms divides into
two and the division continues in multiples of
two.
 Cells of unicellular organisms divide into
separate daughter cells which develop into
adult individuals.
 Cell division starts with division of nucleus
(karyogamy) – chromosomes and then
cytoplasm (cytogamy)
 There are two types of cell division; mitosis
and meiosis

6. Chromosomes
 Are long thread-like structures found in the nucleus
which become visible with microscope only during cell
division.
 Each somatic cell (body cell) has a fixed diploid (double
number) of chromosomes (also referred to as “2n”
constitution) e.g. 23 pairs for human, 4 pairs for
Drosophila, 20 pairs for mouse and 7 pairs for garden
pea.
 Each chromosome is made of two parallel strands called
chromatids. Each chromatid pair is connected at a
point by centromere.

7. Structure of Chromosomes

8. Homologous chromosomes
 This is a pair of chromosomes with a
characteristic length i.e. have a similar
appearance though their genetic
composition may be different.
 Each parent gives one pair of such
chromosomes during sexual reproduction.

9. Homologous chromosomes

10. Genes
 Located along the length of chromosome.
 Are basic units of heredity that are transferred from a
parent to offspring.
 Are made of protein chemical substance called
Deoxyribonucleic acid (DNA), which contain coded
information determine the characteristics of the
offspring e.g. whether male or female.

11. Mitosis
 The type of reproduction in which a cell divides into
two daughter cells each with the same number of
chromosomes as the parent cell.

12. Importance of Mitosis

13. Functions of mitosis
 For simple organisms, it
is a means of asexual
reproduction. (For
example cells of fungus)
 In multicellular
organisms, it allows for
entire cell to grow by
forming new cells and
replacing older cells.
 In certain species,
mitosis is used to heal
wounds or regenerate
body parts.

14. Phases of mitosis
 It is a continuous process, divided into four
phases;
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
 In order to remember the phases easily, we can
use the acronym P-MAT
 However, prior to cell division (P-MAT), the cell
spends a lot of time in INTERPHASE where it
undergoes intense activities in preparation to
division.

15. Interphase
 During interphase;
 The genetic material multiplies so that
daughter cells have the same number of
chromosomes as the parent cell.
 New cell organelles are synthesized e.g. golgi
apparatus, centrioles, mitochondria and
ribosomes.
 Enough energy stores in form of ATP
(adenosine triphosphate) is build up

16. Phases of the Cell Cycle
 Interphase- phase in
which cells spends
most time performing
functions that makes
it unique.
 Mitosis- phase of cell
during which cell
divides into two
daughter cells.

17. Stages

18. Prophase
 In animal cells, duplicated
microscopic bodies called
centrioles separate and move
to opposite sides of the cell.
These are not present in most
plant or fungal cells.
 Spindle fibres begin to form.
 Nuclear membrane begins to
break down and nucleolus
disappear.
 Chromosomes thicken and
shorten and become visible
through staining.

19. Metaphase
 Nuclear membrane disappears
hence chromosomes are found
free in cytoplasm
 Spindle fibres lengthen (they
attach to centrioles by at both
poles in animal)
 Chromosomes align
themselves at equatorial
plate (equator of spindle).
 Each pair is connected at the
centromere where the spindle
fiber is attached.

20. Anaphase
 Spindle fibres shorten,
chromatids move apart
(separate) from each
other and move to the
opposite poles.
 The spindle apparatus
begin to disappear.
 The cell membrane in
animal cells begins to
constrict towards the
end.

21. Telophase
 Chromosomes
finally
arrive/collect
together at the
opposite poles of
the cell.
 Nuclear membrane
forms around set of
chromosomes
 Cytoplasm divides
into two leading to
the formation of
two daughter cells.
 Chromosomes
become less
distinct.

22. Cytokinesis
 Process in which
cytoplasm divides into
two separate cell forms.
 In animal cells, it begins
with the formation of a
furrow in the center of
the cell which constricts
the cell membrane.
 The membrane begins to
pinch into cytoplasm and
formation of two cells
begins. (Process
referred to as cell
cleavage).

23. Plant cell Final Stage
 Cleavage doesn’t
take place.
 New cell wall is
assembled at
center of cell by
formation of
middle lamellae
and separation of
two daughter cells
occurs.

24. The End;
thanks for
walking with me.