Reproduction in Plants and animals

1

Reproduction in Plants and animals

Definition of reproduction

:

Reproduction is

the biological

process by which new

offspring/

individual org

anisms are produced from their parents

. Reproduction is a

characteristic

of all living organisms; each individual or

ganism exists as the result of

reproduction.

Reproduction

is necessary for the

maintenance

of a particular

species

.

There

are two

types

of

reproduction: sexual

and asexual reproduction

and these occur in

both animals and plants.

Definition of asexual repro

duction

: This

is the production of offspring from one parent

without the fusion of the nuclei of the male and female gametes.

Definition of sexual reproduction

: This is the production of offspring from the fusion

of the nuclei of the male and female gamet

es.

Asexual reproduction

.

There are fiv

e types of asexual reproduction:

i)Fission

ii

) Sporulation (

spore formation)

iii

) Budding

iv)Fragmentation

v)

Vegetative

propagation

Fission

This is a type of asexual reproduction

in which the organism after reaching

maturity

divides into two or more equal sized

portions. The

types of fission are binary fission and

multiple fission.

Binary fission

In this process

the organism

divides into 2

equal daughter

cells

only. This

method of

reproduction is common in

amoeba, par

amecium

and

bacteria. In

amoeba and

paramecium the cell division involves mitosis.

Assignment: Draw

the successive stages of reproduction in amoeba from New

Biology for Tropical Schools by Stone and Cozens. Page 12.

Multiple fission

This normally takes pl

ace in parasitic

microbes

e.g.

one malarial parasite

in a

liver cell

undergoes multiple fission to produce 1000 organisms.

Sporulation

This occurs in fungi and bacteria

Sporulation in

Rhizopus

(common mould)

A few days after

Rhizopus

appears on a

piece of

bread, little

black dots are

seen. These

are the sporangia which are borne at the end of

the

sporangiophores.Each sporangium

contains many small

spores, and

when it is ripe

it bursts and the spores are set

free. The

spores are very light and easily blown

by the

wind. If

they fall on a suitable substrate they

germinate and grow into a mycelium.

Assignment: Draw

the mycelium of

Rhizopus

from New Biology for Tropical

Schools by Stone and Cozens. Page 71.

Budding

2

This is the type of reproduction in which an

organism

develops an outgrowth which can

detach itself and develop into a new organism.

Yeast cells

and hydra reproduce by this

method.

Budding in yeast

In suitable conditions

i.e.

enough

food, water,

oxygen and optimum temperatu

re,

yeast

reproduces by

b

udding. Each

cell forms

a projectio

n or bud and its nucleus divides

into

two. One

part of the nucleus moves into the bud which can detach off

the parent

or

remain attached to form a chain

.



Draw the diagram of yeast multiplying by budding from New Biology

for

Tropical Schools by Stone and Cozens. Page 73

.

Fragmentation

This is the type of reproduction in which an organism breaks up into two or more parts

and each part forms an independent individual

by successive cell division

e.g in

spirogyra.This occur

s when

the

conditions are suitable.

Vegetative reproduction/propagation

This is the type of asexual reproduction in which new individuals grow from vegetative

parts of a parent plant. These parts are leaves, stems and roots.

The following are examples of

plants which carry out

vegetative

reproduction.

Name of plant

Part of the plant

Identity

Cassava

Stem

Stem cutting

Sugarcane

Stem

Stem cutting

Banana

Stem

Sucker

Irish potato

Stem

Stem tuber

Sweet potato

Stem and root

Stem cutting and root tuber

Bry

ophyllum

leaf

leaf

Yam

Stem

Stem tuber

Cocoyam

Stem

Corm

Onion

Stem

Bulb

Pineapple

Stem

Sucker

Ginger,Spear grass,Coach

grass,Paspalam

Stem

Rhizome

Strawberry

Stem

Runner

In some cases, the organ for

vegetative reproduction also acts as a food sto

rage

organ so

that a plant can survive

unfavourable

conditions. These

organs are known as perennating

or

gans. For example ;Suckers,

Stem tubers,

Corms,

Rhizomes.



Revise all your S.1 work about the characteristics and diagrams of the above.



Differentiate be

tween a rhizome and a corm.



Research and write notes about

Artificial propagation by use of stem

cuttings,budding,layering,grafting and marcoting

.



Describe the advantages and disadvantages of vegetative reproduction.