Chapter 9 Reproduction in Animals Class 8 Notes | EduRev

Science - Short Notes for Class 8th

Created by: Sushil Solanki

Class 8 : Chapter 9 Reproduction in Animals Class 8 Notes | EduRev

 Page 1


Chapter 9 
Reproduction in Animals 
 
Reproduction – The process of producing young ones of one’s own kind. 
Modes of Reproduction 
1. Asexual Reproduction 
2. Sexual Reproduction 
 
Asexual Reproduction 
 
A mode of reproduction in which a single parent is involved (no mother father just one mother) 
Examples of asexual reproduction 
1. Budding in Hydra 
Buds are small outgrowths coming out of an organism that are capable of forming the complete 
organism. 
 
 
 
                                                                                        
 
 
 
 
 
 
 
 
 
Fig.1 Budding in Hydra 
 
The fully-grown bud falls down can develops into a complete daughter Hydra 
 
 
 
 
Immature hydra 
Bud 
Outgrowth initiation 
Page 2


Chapter 9 
Reproduction in Animals 
 
Reproduction – The process of producing young ones of one’s own kind. 
Modes of Reproduction 
1. Asexual Reproduction 
2. Sexual Reproduction 
 
Asexual Reproduction 
 
A mode of reproduction in which a single parent is involved (no mother father just one mother) 
Examples of asexual reproduction 
1. Budding in Hydra 
Buds are small outgrowths coming out of an organism that are capable of forming the complete 
organism. 
 
 
 
                                                                                        
 
 
 
 
 
 
 
 
 
Fig.1 Budding in Hydra 
 
The fully-grown bud falls down can develops into a complete daughter Hydra 
 
 
 
 
Immature hydra 
Bud 
Outgrowth initiation 
 
2. Binary fission in Amoeba 
 
Amoeba is a microorganism that reproduce by binary fission. 
Binary fission is the process of reproduction in which an organism divides into two daughter cells.  
 
 
 
 
 
 
 
 
 
 
 
 
 
                 Fig. 2 Binary fission in Amoeba 
 
 
 
Sexual Reproduction 
 
A type of reproduction in which two parents are involved (male and female). Male and female gametes (sex 
cells) fuse to form a zygote (another cell) which develops in to a young one (baby) by continuous (repeatedly) 
division. 
Zygote – A single cell formed by fusion of male gamete also known as sperm and female gamete also known as 
ovum. 
Gametes – Sex cells are also known as gametes. Male gamete is known as sperm and female gamete is known 
as ovum or egg. 
 
Amoeba cell 
Nucleus dividing 
Cytoplasm dividing 
Two daughter cells 
Page 3


Chapter 9 
Reproduction in Animals 
 
Reproduction – The process of producing young ones of one’s own kind. 
Modes of Reproduction 
1. Asexual Reproduction 
2. Sexual Reproduction 
 
Asexual Reproduction 
 
A mode of reproduction in which a single parent is involved (no mother father just one mother) 
Examples of asexual reproduction 
1. Budding in Hydra 
Buds are small outgrowths coming out of an organism that are capable of forming the complete 
organism. 
 
 
 
                                                                                        
 
 
 
 
 
 
 
 
 
Fig.1 Budding in Hydra 
 
The fully-grown bud falls down can develops into a complete daughter Hydra 
 
 
 
 
Immature hydra 
Bud 
Outgrowth initiation 
 
2. Binary fission in Amoeba 
 
Amoeba is a microorganism that reproduce by binary fission. 
Binary fission is the process of reproduction in which an organism divides into two daughter cells.  
 
 
 
 
 
 
 
 
 
 
 
 
 
                 Fig. 2 Binary fission in Amoeba 
 
 
 
Sexual Reproduction 
 
A type of reproduction in which two parents are involved (male and female). Male and female gametes (sex 
cells) fuse to form a zygote (another cell) which develops in to a young one (baby) by continuous (repeatedly) 
division. 
Zygote – A single cell formed by fusion of male gamete also known as sperm and female gamete also known as 
ovum. 
Gametes – Sex cells are also known as gametes. Male gamete is known as sperm and female gamete is known 
as ovum or egg. 
 
Amoeba cell 
Nucleus dividing 
Cytoplasm dividing 
Two daughter cells 
 
 
 
 
 
 
 
Fig. 3 Human Sperm                                            Fig. 4 Human Ovum or egg 
 
 
Fertilization 
The fusion of male and female gamete to form a zygote is known as fertilization. As soon as one sperm enters 
the ovum, the cell membrane of the ovum blocks the entry of any other sperms. 
 
 
 
 
 
 
                                              Fig. 5 Entry of a sperm into the ovum 
 
 
 
 
                                                
                                                Fig. 6 Zygote 
 
 
Types of fertilization 
 
1. Internal fertilization – A type of fertilization in which the sperm and the ovum fertilizes inside the 
female body. E.g. fertilization in cat, dogs, hens and humans. 
Nucleus 
Cytoplasm 
Page 4


Chapter 9 
Reproduction in Animals 
 
Reproduction – The process of producing young ones of one’s own kind. 
Modes of Reproduction 
1. Asexual Reproduction 
2. Sexual Reproduction 
 
Asexual Reproduction 
 
A mode of reproduction in which a single parent is involved (no mother father just one mother) 
Examples of asexual reproduction 
1. Budding in Hydra 
Buds are small outgrowths coming out of an organism that are capable of forming the complete 
organism. 
 
 
 
                                                                                        
 
 
 
 
 
 
 
 
 
Fig.1 Budding in Hydra 
 
The fully-grown bud falls down can develops into a complete daughter Hydra 
 
 
 
 
Immature hydra 
Bud 
Outgrowth initiation 
 
2. Binary fission in Amoeba 
 
Amoeba is a microorganism that reproduce by binary fission. 
Binary fission is the process of reproduction in which an organism divides into two daughter cells.  
 
 
 
 
 
 
 
 
 
 
 
 
 
                 Fig. 2 Binary fission in Amoeba 
 
 
 
Sexual Reproduction 
 
A type of reproduction in which two parents are involved (male and female). Male and female gametes (sex 
cells) fuse to form a zygote (another cell) which develops in to a young one (baby) by continuous (repeatedly) 
division. 
Zygote – A single cell formed by fusion of male gamete also known as sperm and female gamete also known as 
ovum. 
Gametes – Sex cells are also known as gametes. Male gamete is known as sperm and female gamete is known 
as ovum or egg. 
 
Amoeba cell 
Nucleus dividing 
Cytoplasm dividing 
Two daughter cells 
 
 
 
 
 
 
 
Fig. 3 Human Sperm                                            Fig. 4 Human Ovum or egg 
 
 
Fertilization 
The fusion of male and female gamete to form a zygote is known as fertilization. As soon as one sperm enters 
the ovum, the cell membrane of the ovum blocks the entry of any other sperms. 
 
 
 
 
 
 
                                              Fig. 5 Entry of a sperm into the ovum 
 
 
 
 
                                                
                                                Fig. 6 Zygote 
 
 
Types of fertilization 
 
1. Internal fertilization – A type of fertilization in which the sperm and the ovum fertilizes inside the 
female body. E.g. fertilization in cat, dogs, hens and humans. 
Nucleus 
Cytoplasm 
2. External fertilization - A type of fertilization where the fusion of sperm and ovum takes place outside 
the body. For e.g. fertilization in frog, mosquito.  
A female frog lays hundreds of eggs and the male frog deposits sperms on them. Each sperm randomly 
fuses with one egg producing hundreds of tadpoles. 
 
 
                              Fig. 9 Life Cycle of a frog 
 
Metamorphosis – The drastic change occurring in some organisms such as frog and butterfly from the larvae 
stage to the adult stage. 
Oviparous and Viviparous Organisms 
Oviparous animals – Animals that lay eggs. E.g. lizard, frog, hen, duck etc. 
Viviparous animals – Animals that give birth to young ones. E.g. Humans, elephant, dog, cat etc. 
 
Male and Female reproductive organs 
 
 
 
 
 
 
 
 
 
 
 Fig.7 Male Reproductive Organs     Fig 8 Female Reproductive Organs 
Testes 
Duct 
Vagina 
Page 5


Chapter 9 
Reproduction in Animals 
 
Reproduction – The process of producing young ones of one’s own kind. 
Modes of Reproduction 
1. Asexual Reproduction 
2. Sexual Reproduction 
 
Asexual Reproduction 
 
A mode of reproduction in which a single parent is involved (no mother father just one mother) 
Examples of asexual reproduction 
1. Budding in Hydra 
Buds are small outgrowths coming out of an organism that are capable of forming the complete 
organism. 
 
 
 
                                                                                        
 
 
 
 
 
 
 
 
 
Fig.1 Budding in Hydra 
 
The fully-grown bud falls down can develops into a complete daughter Hydra 
 
 
 
 
Immature hydra 
Bud 
Outgrowth initiation 
 
2. Binary fission in Amoeba 
 
Amoeba is a microorganism that reproduce by binary fission. 
Binary fission is the process of reproduction in which an organism divides into two daughter cells.  
 
 
 
 
 
 
 
 
 
 
 
 
 
                 Fig. 2 Binary fission in Amoeba 
 
 
 
Sexual Reproduction 
 
A type of reproduction in which two parents are involved (male and female). Male and female gametes (sex 
cells) fuse to form a zygote (another cell) which develops in to a young one (baby) by continuous (repeatedly) 
division. 
Zygote – A single cell formed by fusion of male gamete also known as sperm and female gamete also known as 
ovum. 
Gametes – Sex cells are also known as gametes. Male gamete is known as sperm and female gamete is known 
as ovum or egg. 
 
Amoeba cell 
Nucleus dividing 
Cytoplasm dividing 
Two daughter cells 
 
 
 
 
 
 
 
Fig. 3 Human Sperm                                            Fig. 4 Human Ovum or egg 
 
 
Fertilization 
The fusion of male and female gamete to form a zygote is known as fertilization. As soon as one sperm enters 
the ovum, the cell membrane of the ovum blocks the entry of any other sperms. 
 
 
 
 
 
 
                                              Fig. 5 Entry of a sperm into the ovum 
 
 
 
 
                                                
                                                Fig. 6 Zygote 
 
 
Types of fertilization 
 
1. Internal fertilization – A type of fertilization in which the sperm and the ovum fertilizes inside the 
female body. E.g. fertilization in cat, dogs, hens and humans. 
Nucleus 
Cytoplasm 
2. External fertilization - A type of fertilization where the fusion of sperm and ovum takes place outside 
the body. For e.g. fertilization in frog, mosquito.  
A female frog lays hundreds of eggs and the male frog deposits sperms on them. Each sperm randomly 
fuses with one egg producing hundreds of tadpoles. 
 
 
                              Fig. 9 Life Cycle of a frog 
 
Metamorphosis – The drastic change occurring in some organisms such as frog and butterfly from the larvae 
stage to the adult stage. 
Oviparous and Viviparous Organisms 
Oviparous animals – Animals that lay eggs. E.g. lizard, frog, hen, duck etc. 
Viviparous animals – Animals that give birth to young ones. E.g. Humans, elephant, dog, cat etc. 
 
Male and Female reproductive organs 
 
 
 
 
 
 
 
 
 
 
 Fig.7 Male Reproductive Organs     Fig 8 Female Reproductive Organs 
Testes 
Duct 
Vagina 
Functions of various organs 
Male Reproductive organs 
a. Testes – produces sperms 
b. Sperm Duct – Carries sperms to penis 
c. Penis  - Releases sperms into female reproductive system 
 
Female Reproductive Organs 
a. Vagina – Receives sperms from the male reproductive system  
b. Oviduct – Place of fertilization  
c. Ovaries – Releases one egg every month 
d. Uterus – Zygote is implanted. Zygote divides to form the embryo (foetus, baby) 
Steps involved in Reproduction 
 
Sperms are released into the female reproductive system if there is copulation (sex) 
 
Sperms swim to oviduct through uterus 
(One ovum is released in the oviduct every month) 
Uterus prepares itself every month for implantation by forming layers of blood and mucus. 
 
 
 
 
 
Zygote is formed 
Zygote is implanted in the uterus 
Zygote divides millions of times to form and 
embryo which further forms the foetus 
Embryo – The dividing zygote forms a group of 
cells, which is differentiating to form tissues and 
organs. This structure is called the embryo. 
Foetus – The stage of embryo when various organs 
can be identified. 
 
The walls of the uterus deters, which results in the 
excretion of blood and mucus from the vagina.  
This process continues for 3-4 days and is also 
known as periods in local language. 
The cycle repeats every month (approximately 30 
days). In case there is no fertilization, blood and 
mucus are released at the end of every month 
 
 
 
 
If sperm fertilizes 
with the ovum 
 If there is no fertilization 
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