Reproduction In Animals Flashcards
1
Q
What is reproduction?
A
Reproduction is a biological process by which an organism reproduces an offspring that is biologically similar to the organism.
2
Q
Why is reproduction considered the main feature of life on earth and one of the most important characteristics of living organisms?
A
By the process of reproduction, living organisms produce young ones of their own kind and therefore it is also responsible for the continuation of species even after death of an individual
3
Q
What are the two modes of reproduction?
A
ASEXUAL AND SEXUAL
4
Q
What is sexual reproduction?
A
Sexual reproduction is the production of a new individual from existing two parents by the fusion of their gametes.
5
Q
How is a young one produced in sexual reproduction?
A
When a male gamete fuses with a female gamete, it forms a zygote that develops into a new individual.
6
Q
Give examples of species that undergo sexual reproduction.
A
COWS, DOGS, HUMAN BEINGS, HORSES, etc.
7
Q
What is asexual reproduction?
A
Asexual reproduction is the production of a new individual from a single parent without the involvement of gametes
8
Q
Does a zygote also get formed in asexual reproduction?
A
Since fusion of gametes does not take place in asexual reproduction, hence, zygotes are not formed.
9
Q
What is the main distinct characteristic of asexual reproduction?
A
The young ones produced by asexual reproduction are exact copies of their parents.
10
Q
Give examples of species that undergo asexual reproduction.
A
YEAST & HYDRA, ETC.
11
Q
How many organisms are involved in asexual reproduction? WHY?
A
In sexual reproduction, two parent organisms, one male and one female are involved because they have different reproductive parts or organs that are equally important to carry out the process.
12
Q
What does male reproductive system consist of?
A
The male reproductive system consists of a pair of testes (singular: testis), two sperm ducts (vas deferens), urethra and penis.
13
Q
How many testes are there in a man?
A
There are two testes in a man.
14
Q
What is the shape of testes?
A
These testes are oval-shaped.
15
Q
What does testes produce?
A
They produce the male gametes called sperms. (also testosterone)
16
Q
What are SCROTAL SACS?
A
Testes lie outside the abdominal cavity in two small muscular bags of skin called SCROTAL SACS.
17
Q
What are SCROTAL SACS responsible for?
A
SCROTAL SACS acts as thermoregulators and keep the temperature of testes about 2-3 degree Celsius lower than the body temperature.
18
Q
Why do SCROTAL SACS maintain such temperature?
A
SCROTAL SACS maintain such temperature because the testes work more efficiently at a temperature lower than the body temperature.
19
Q
What is TESTOSTERONE?
A
A male sex hormone called TESTOSTERONE is also produced from the testes
20
Q
When does a man start producing sperms?
A
Sperms start producing in the testes when a man reaches at the age of 11-12 years.
21
Q
How many sperms does a healthy man produce each day?
A
A healthy man produces about 2 billion sperms everyday.
22
Q
What are sperms? What does it consist of?
A
A sperm is a very small microscopic particle which contains a head. middle piece and a tail.
23
Q
How does the sperm reach the female gamete?
A
A sperm can swim easily and move towards the female gamete with the help of its tail.
24
Q
What is EPIDIDYMIS?
A
There is a coiled tube like structure called the EPIDIDYMIS which is firmly attached to the testis.
25
What is an EPIDIDYMIS responsible for?
The sperm gets stored temporarily in EPIDIDYMIS until it matures.
26
What are sperm ducts?
The sperm ducts are the narrow ducts which join the testes to the urethra through seminal vesicles.
27
What work do sperm ducts perform?
Sperm ducts carry matured sperms from the epididymis to the seminal vesicles where sperms get stored.
28
How is semen produced?
A fluid is produced by the seminal vesicles which mixes with the sperms to produce semen.
29
What is the work of a semen?
Semen provides nourishment to the sperms
30
Where does the seminal vesicle join?
Seminal vesicles join to another tube called urethra.
31
What is urethra?
It is a long tube arising from the urinary bladder which carries urine.
32
What does the urethra carry and to where?
Urethra carries the sperms to an organ called penis
33
Where is the open end of the penis situated?
The penis opens outside the body through a pore.
34
What functions does the urethra perform?
Urethra carries semen consisting of sperms from the sperm ducts and urine from the bladder through the penis.
35
What is a penis?
It is a long and thick muscular organ
36
What is insemination?
The penis injects the sperms into the vagina of the female body for reproduction. This process is known as insemination.
37
What does the male reproductive system also consist of?
The male reproductive system also has some glands
38
What does the female reproductive system consist of?
The female reproductive systems consists of a pair of ovaries, oviducts (fallopian tubes), uterus (womb), and vagina.
39
How many ovaries are there in a women?
There are TWO ovaries in a women.
40
What is the shape of an ovary?
OVAL-SHAPED
41
Where are the ovaries situated?
Ovaries are present in the abdominal cavity.
42
What functions does the ovary perform?
Ovaries make the female gametes called OVA or EGGS and also secrete female sex hormone called ESTROGEN and PROGESTERONE.
43
What is a OVARIAN LIGAMENT?
Ovaries are attached to the uterus through a fibrous cord called OVARIAN LIGAMENT.
44
What happens in the female reproductive system during puberty?
In women at puberty, a single mature egg is released into the oviduct alternatively by one of the ovaries every month.
45
What is the size of an egg?
Like the sperm, an egg is also a single cell but it is much bigger than the sperm.
46
Why does the uterus have muscular tissues?
The uterus have muscular tissues. During pregnancy, these muscular tissues expand to hold the growing foetus and after birth of the baby, these muscular tissues contract.
47
What is an oviduct?
Oviduct is a thin muscular tube having a funnel shaped opening near the ovaries which joins the uterus to the ovary.
48
What happens when an ovum is released by an ovary?
When the ovum (or egg cell) is released by an ovary, it goes into the the fallopian tube through its funnel-shaped opening.
49
Where does the fertilization of egg take place?
In the fallopian tube, fertilization of egg takes place
50
What is an uterus?
There is a bag-like organ where the two fallopian tubes connect. It called the UTERUS (womb).
51
What happens in the uterus?
In the uterus, the growth and development of a fertilized egg into a baby takes place.
52
Are the size of eggs in animals the same?
The size of eggs in animals vary. The egg maybe very small in humans and much larger in hens.
53
Which animal produces the largest egg?
OSTRICH
54
What is the vagina and cervix?
The uterus is connected to a wide muscular tube called VAGINA through a narrow opening called CERVIX.
55
Where is the open end of the vagina situated?
Vagina opens towards the outside of the body.
56
What function does the vagina perform?
The function of the vagina is to facilitate the entry of the penis so that insemination can take place.
57
What does the female reproductive system also consists of?
The female reproductive system also has some glands.
58
How many steps are involved in the human reproductive system?
In humans, reproduction takes place in two steps, i.e.:
1. FERTILIZATION
2. DEVELOPMENT OF EMBRYO
59
What happens in humans during mating?
1. In human beings, the sperms formed in the testes of man are injected by the penis into the female's body through the vagina during mating.
2. From vagina, they enter the uterus and then to the oviducts.
3. If, at the same time, the ovary of the women releases egg, then this egg also enters the oviduct.
4. One of the sperms enters the egg where the nucleus of the sperm fuses with the nucleus of the egg cell to form a single nucleus called the ZYGOTE in the oviduct.
60
What is fertilization?
The fusion of a male gamete or sperm with the female gamete or egg (ovum) to form a zygote is called FERTILIZATION.
61
What is zygote?
ZYGOTE is a fertilized egg that forms after fertilization in the fallopian tube. It is the first cell of a new individual
62
What are the characteristics of the new individual?
The new individual inherits some characteristics from the mother and some from the father.
63
Where does fertilization take place?
Fertilization can take place either inside the body or outside the body of a female.
64
HOW MANY and what are the types of fertilization taken place in animals?
Two types of FERTILIZATION taken place in animals:
1. Internal 2. External
65
What is external fertilization?
When the male gamete fuses with the female gamete to produce a zygote outside the female's body, it is called EXTERNAL FERTILIZATION.
66
Where does external fertilization mostly take place?
External fertilization mostly takes place in aquatic environments.
67
Provide examples of animals that perform external fertilization?
Frogs, toads, fish and starfish
68
How does external fertilization take place? Explain with a suitable example.
1. Frogs and toads move towards the ponds or any source where water is flowing slowly.
2. The male and female frogs come close to each other.
3. The female frogs lays many eggs after their mating.
4. These eggs are covered by jelly like covering as these eggs are without any shell.
5. The male frog releases sperms over them.
6. With the release of eggs, the sperms reach to the egg with the help of long tail and fertilize the egg.
THIS IS AN EXAMPLE OF EXTERNAL FERTILIZATION.
69
Can sperms enter the egg after its fertilization?
In humans, after fertilization a covering known as the fertilization membrane is formed around the fertilized egg which prevents other sperms from entering it.
70
What happens when egg is not fertilized?/ What is menstruation?
In case the egg is not fertilized, the egg and the thickened lining of the uterus along with its blood vessels are shed off. This is known as MENSTRUATION WHICH OCCURS ONCE IN ABOUT 28 TO 30 DAYS.
71
What is internal fertilization?
When the male gamete fuses with the female's gamete inside the female's body is called INTERNAL fertilization
72
Provide examples of animals that perform internal fertilization?
Human beings, cows, dogs, birds, hens and reptiles.
73
How does internal fertilization take place in human beings?
In internal fertilization, the male releases sperms into the female's body. The sperms then moves to the egg and fertilize it to form zygote.
74
Which type of fertilization does hens perform?
-- In case of hens, internal fertilization take place.
-- Hens lay eggs
-- They sit on their fertilized eggs for a considerable time to give them warmth.
-- During this time, the zygote grows and develops to form a chick which comes out of the egg by breaking its shell.
75
What does the term test tube baby mean?
The term TEST TUBE BABY refers to a child whose zygote is fertilized outside the mother's body in a glass dish.
76
Which kind of a process is this?
SCIENTIFIC Process
77
What is this process also known as?
This process is also known as IN-VITRO FERTILIZATION or IVF.
78
What happens in this process?
- The complete process is done from the mother's ovary by surgical methods and fertilized by the sperm from father or any other healthy donor (IN CASE OF INFERTILE COUPLES)
- Then, the fertilized egg is cultured for at least 1 week and allowed to form 4-8 cells inside their dish or test tube.
- Then, this zygote is transferred into the mother's womb like normal pregnancy.
- In mother's womb, it develops normally.
79
Why are the test tube babies called so?
The test tube babies are called so because this fertilization was carried inside the test tube or glass dish in a laboratory.
80
For whom is this process helpful?
This process is helpful for those women who are not able fertilize their eggs inside their ovary.
81
Why is the term 'test tube babies' misleading?
Note that babies cannot grow in test tubes. They grow in the uterus of the women except for a period of about one week after fertilization. So, this term is actually misleading.
82
Why does animals like fish or frogs produce so many eggs?
>> Animals like frog and fish lay hundreds of eggs whereas a hen lays only one egg at a time.
>> Out of hundreds of eggs laid by the frog or fish, only a few will survive and become adult frog or fish because many of the eggs are carried away by moving water, wind and rainfall and many of them are eaten by other animals.
>> Due to this reason, a large number of production of eggs of frog or fish is necessary to ensure the fertilization.
83
What are viviparous animals?
The animals which give birth to young ones are called VIVAPAROUS ANIMALS
84
Provide examples of viviparous animals.
Humans, dogs, cats, cows, etc.
85
What are oviparous animals?
The animals which lay eggs are called OVIPAROUS ANIMALS
86
Provide examples of oviparous animals.
Frogs, Lizards, butterflies , hens etc.
87
Why is the eggs of oviparous animals visible while the viviparous animals' is not?
The eggs of oviparous animals are easy to observe as their mothers lay them outside their bodies.
88
How does the sperm know where to go?
The chemical signals produced by the ovum guide the sperms throughout its journey.
89
How does the sperm fertilize the nucleus of the egg?
The female ovum has two layers of protection:
- inner cover- ZONA PELLUCIDA
- outer cover- CORONA RADIATA
The sperm has to break through these layers to carry out fertilization.
90
How many chromosomes does the zygote have after fusion of the sperm and ovum nuclei
>> A sperm and egg cell each contain 23 chromosomes, during fertilization which is half the number of chromosomes in regular cells. When the sperm and egg join during fertilization, the resulting zygote has 46 chromosomes (23 pairs) containing the contribution of half of the genetic information for the offspring by each parent.
>> The process of cell division known as MEIOSIS, ensures that humans have the same number of chromosomes in each generation. It is a two-step process that reduces the chromosome number by half—from 46 to 23- for preparing both sperm and ovum cells for fertilization
91
What is the purpose of MEIOSIS?
>>The process of cell division known as MEIOSIS, ensures that humans have the same number of chromosomes in each generation.
>> The purpose of meiosis is the production of gametes for sexual reproduction and creating genetic diversity.
>> Meiosis s a two-step process that reduces the number of chromosomes in a cell by half—from 46 to 23- for making both sperm and ovum cells, so that when a sperm and egg fuse, the resulting zygote has the correct number of chromosomes. Without meiosis, the number of chromosomes would double with each generation, leading to genetic abnormalities.
92
How is the sex of the zygote determined?
In humans, the sex of the offspring is determined by which chromosome from the male gamete fuses with which chromosome from the female gamete:
-- When the X chromosome from the male gamete fuses with the X chromosome of the female gamete, the zygote will develop into a girl.
-- When the Y chromosome from the male gamete fuses with the X chromosome of the female gamete, the zygote will develop into a boy.
NOTE: All ovum has 1 pair of X sex chromosomes while sperm has a pair of both Y and X sex chromosome.
93
How is the growing embryo transported from oviduct to the uterus?
The egg cell is transported inside the fallopian tube with the help cilia and mucus produced by the glands of the fallopian tube. Additional contractions of muscle layers help to transport the ovum.
94
What happens to the zygote after fertilization?
After fertilization, zygote is formed which gradually develops into an embryo:
> after the formation of zygote, cleavage (division of cells) occurs.
> as the repeated division of zygote continues into 2, 4 and 8 celled embryo, it travels down the fallopian tube, where it becomes a morula (16-32 celled stage of embryo- represents a mulberry)
> Once it reaches the uterus, the morula (after 32-celled stage) becomes a blastocyst which is a fluid filled sac. The embryoblast of blastocyst contains the initial structure of a new human being.
> The blastocyst then burrows into the uterine wall — a process called implantation.
> after implantation of blastocyst is complete, gastrulation occurs- formation of germ layers:
i. ECTODERM (outer layer):
internal lining of organs
ii. MESODERM (middle layer):
nervous system
iii. ENDODERM (inner layer):
blood vessels, bones and muscles
> At last the development of embryo continues in the uterus until it forms the foetus.
95
How does the blastocyst get implanted?
The blastocyst hatches out of its zona pellucida and attaches to the thick lining of the endometrium. The blastocyst then buries/ embeds itself deeper into the uterine wall which may lead to harmless bleeding
96
What is an EMBRYO?
The zygote divides repeatedly and forms a ball of cells. These cells then begin to form groups that develop into different tissues and organs of the body. This developing structure is called an embryo.
97
From where does the embryo get nourishment?
>> The trophoblast of blastocyst is the origin of placenta and membrane implantation of blastocyst in the posterior wall of the uterus which nourish the embryo resulting in increasing cell mass which may lead to harmless bleeding during implantation.
>> During implantation, the trophoblast cells of the blastocyst fuse with the endometrial cells to form the placenta.
>> The placenta attaches the embryo or which later forms into the foetus to the uterus and provides oxygen and nutrients in both the stages from the blood vessels of the mother.
98
Are the body features developed in the embryo stage?
The body features at the embryo stage (about first eight weeks of pregnancy) are not much developed.
99
What is FOETUS?
-- After several divisions, the embryo completes its development in the uterus.
-- It develops all parts of the body one-by-one like head, eyes, ears, nose, face, hands, legs, etc.
-- Once, all parts of the body can easily be identified in embryo, it is further called a FOETUS.
-- It is attached to the uterus by a structure called PLACENTA which provides oxygen and nutrients to the foetus.
100
What is gestation period?
In humans, it takes the periods of 9 months or 40 weeks for the complete development of the foetus from the fertilization of egg to the birth of a baby. This period is called GESTATION PERIOD.
101
What happens after complete development of the foetus?
When the development of the foetus has been completed, the mother gives birth to the baby. This shows how humans reproduce by giving birth to the babies.
102
Hens undergo internal fertilization, does that mean they also produce young ones like humans?
In hens, internal fertilization takes place, but hens do not give birth to babies like human beings.
103
How does the zygote form into an embryo inside a hen?
-- In hens, male and female gamete fuse to form zygote inside the female's body.
-- Zygote thus formed undergoes repeated division and moves down the fallopian tube to form an embryo.
104
When do the hens lay their eggs?
-- During the development of the zygote to an embryo, the zygote gets surrounded by several protective layers around it.
-- After that, a white-coloured hard shell surrounds the developing embryo.
-- This is the time when a hen lays its eggs.
105
Do the hens lay unfertilized egg outside their body?
No, the hens lay fertilized eggs.
106
What is hatching?
-- The parent sits and warms the eggs.
-- After 8 weeks, the chick comes out of the egg shell after bursting it.
-- This process from warming up the egg to the development of baby chick when it comes out is called HATCHING.
107
What happens after new individuals are formed?
Once the new individual borns, it continues to grow until it reaches maturity and gets transformed into an adult.
108
What is the exceptional structure of some animals from their younger self to their older self?
In most of the animals, the young ones have same structure as their parents have but in some animals, the young ones look very different from the adults.
109
Provide examples of animals who have these different stages of development.
Animals like silkworms, frogs, mosquitoes, and butterflies have different stages of development from the egg to the adult stage.
110
How does the development of a frog occur?
>> A female frog lays many eggs in water.
>> After some time, the eggs hatch into larvae called TADPOLES which looks like small fish.
>> They feed on algae and plants and grow larger.
>> The tadpole develops gradually and undergoes many drastic changes in appearance before it transforms into an adult frog.
>> The tadpole looks very different from the adult frog.
>> The transformation of the larva into an adult through drastic changes is called METAMORPHOSIS.
111
Make a flow chart to demonstrate the different stages of development of a frog.
Different stages of a frog starting from the egg to the adult stage are given below:
Egg (Hatching)---------> TADPOLE (larva)---------> (Metamorphosis) Adult
112
What is the difference between a tadpole and an adult frog?
The features which are present in an adult frog are not present in its tadpole.
113
Make a flow chart to demonstrate the different stages of development of a Silk Moth.
Egg---> larva or caterpillar -----> pupa-----> Adult
114
What is the difference between an adult moth and its larva?
The features which are present in an adult moth are not present in its larva.
115
How does the development of a SILK MOTH justify as an example of metamorphosis? OR
How does the development of a SILK MOTH occur?
-- The caterpillar develops gradually and undergoes drastic changes in appearance before it transforms into an adult silk moth.
-- So, the transformation of a caterpillar to a silk moth is an example of METAMORPHOSIS.
116
Why doesn't human beings undergo metamorphosis?
Human beings do not undergo metamorphosis because in human beings, the body parts in adults are similar to those which are present in their young ones from the time of birth.
