1
Question
Fill in the blanks:
(a) Humans reproduce _____________ (asexually/sexually)
(b) Humans are _____________ (oviparous, viviparous, ovoviviparous)
(c) Fertilisation is _____________ in humans (external/internal) (d) Male and female gametes are _____________ (diploid/haploid)
(e) Zygote is _____________ (diploid/haploid)
(f) The process of release of ovum from a mature follicle is called _____________
(g) Ovulation is induced by a hormone called _____________
(h) The fusion of male and female gametes is called _____________
(i) Fertilisation takes place in _____________
(j) Zygote divides to form _____________which is implanted in uterus.
(k) The structure which provides vascular connection between foetus and uterus is called _____________
(a) Humans reproduce _____________ (asexually/sexually)
(b) Humans are _____________ (oviparous, viviparous, ovoviviparous)
(c) Fertilisation is _____________ in humans (external/internal) (d) Male and female gametes are _____________ (diploid/haploid)
(e) Zygote is _____________ (diploid/haploid)
(f) The process of release of ovum from a mature follicle is called _____________
(g) Ovulation is induced by a hormone called _____________
(h) The fusion of male and female gametes is called _____________
(i) Fertilisation takes place in _____________
(j) Zygote divides to form _____________which is implanted in uterus.
(k) The structure which provides vascular connection between foetus and uterus is called _____________
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Solution
a.Reproduction:
The process by which an organism produces its offsprings is called reproduction.
Types of reproduction:
Reproduction can be further classified into two types:
a. Sexual reproduction -The type of reproduction which involves two parents and fusion of gametes is called sexual reproduction . For example,reproduction in Human beings
b. Asexual reproduction - This type of reproduction does not involve two parents and fusion of gametes. Here the offspring produced are identical to the parents and are referred to as clones. For example - Amoeba reproduces by binary fission, wherein an Amoeba divides itself into two daughter cells. This process does not involve fusion of gametes.
Sexual reproduction in human being :
In the fallopian tube present in the female reproductive system, the male gamete (sperm) fuses with female gamete (ovum) and gives rise to zygote. This process is called fertilisation. The zygote further develops into a multicellular human. Thus human beings reproduce sexually.
b.Introduction:
There are five classes under phylum chordata - fish, amphibians, reptiles, mammals and birds. Members of these classes that reproduce sexually, either give birth to young ones directly (viviparous) or lay eggs (oviparous) or in some cases the egg hatches within the organism and it gives birth to young one (ovoviviparous).
Oviparous:
Sexually reproducing organisms that lay eggs and the development of the zygote occurs within the egg. Such organisms are called oviparous.
Eg : Birds
Viviparous:
Sexually reproducing organisms like humans, that give birth to young ones directly. In this case the development of the zygote occurs within the body of the organism. Such organisms are called viviparous.
Ovoviviparous:
In some sexually reproducing organisms the egg hatches within the organism and gives birth to young ones. Such organisms are called ovoviviparous. Example- sharks.
c.Fertilisation:
The process of fusion of male and female gamete that gives rise to unicellular zygote is called fertilization.
Types of fertilisation :
Based on where the fertilisation occurs, it can be classified into two types -
a. Internal fertilisation - fusion of male and female gametes occurs within the body. Example - human
b. External fertilisation - fusion of male and female gametes occurs outside the body. Example- frog
Fertilisation in Human:
In human beings, the male gamete (sperms) is transferred to the female reproductive system. The sperm fuses with the ovum at the ampulla in the fallopian tube of the human female reproductive system.
Thus fertilisation in humans is internal.
d.Ploidy:
Total number of set of chromosomes present in a cell is called ploidy.It is represented by n.
Diploid:
If a cell has two sets of chromosomes it is called diploid. It is represented by 2n.
For example, in humans, the body cells have two sets of chromosomes. Each set has 23 chromosomes in it.
Haploid:
If the ploidy of the cell is half its original number, it is called haploid. For example,in humans, the male and female gametes are produced by meiosis. Thus the chromosome content in these cells are half of the other body cells. Thus gametes are haploid cells.
e.Fertilisation:
The fusion of male and female gametes is called fertilisation. Zygote is the product formed as a result of fertilisation.
Ploidy of zygote:
The gametes are formed as a result of meiosis. Thus the number of chromosomes is half of the number of chromosomes in the somatic cells. Therefore gametes are haploid.
Since zygote is formed due to the fusion of two haploid gametes, it is diploid. Which implies zygote has two sets of chromosomes, one set from each parent.
f.Formation of Ovum:
Ovary is the female gonad that produces the ovum. The process of formation of ovum is called oogenesis. This process occurs in multiple steps. The ovary consists of multiple cells called the follicles. Eventually these follicles form a mature follicle called the graafian follicle, that consists of the ovum.
Ovulation:
When the concentration of luteinizing hormone reaches its peak, the graafian follicle ruptures and releases the ovum.The process of release of ovum from a mature follicle is called ovulation.
g.Ovulation:
The process of release of ovum from a mature follicle is called ovulation. The process of formation of mature ovum is called oogenesis. From oogenesis to ovulation, all the processes are regulated by different hormones.
FSH and LH are the two pituitary hormones that are involved in regulating oogenesis and ovulation respectively.
When the LH levels reach their peak, ovulation occurs.
h.Fertilisation:
The fusion of male and female gamete which are haploid cells gives rise to a diploid, unicellular cell called the zygote. The zygote further develops into an embryo and eventually gives rise to an organism.
i.Fertilisation:
The process of fusion of male and female gametes is called fertilisation. This occurs in sexually reproducing organisms.
Types of fertilisation:
Based on where the fertilisation occurs, it can be classified into two types:
a. Internal fertilisation - fusion of male and female gametes occurs within the body. Example - human.
b. External fertilisation - fusion of male and female gametes occurs outside the body. Example- frog.
Fertilisation in human:
In human beings, the male gamete (sperms) is transferred to the female reproductive system. Then the sperm fuses with the ovum at the ampulla in the fallopian tube of the human female.
Thus fertilisation in human is internal.
j.Introduction:
The zygote is a unicellular diploid cell that undergoes cleavage as it travels from the site of fertilisation in the fallopian tube to the uterus. Cleavage is a type of cell division wherein the cell does not increase in mass,but it divides to form multiple smaller cells within one large single cell. These smaller cells are called blastomeres.
Development of zygote:
The zygote undergoes cleavage and give rise to 2 celled stage, 4 celled stage, 8 celled stage and 16 celled stage. Once it reaches the 16 celled stage, the blastomeres rearrange as outer trophoblast and inner cell mass. During this stage a cavity called blastocoel develops. The structure thus formed is called blastocyst. This blastocyst embeds in the endometrial lining of the uterus giving rise to the embryo. This process is called implantation
Thus the zygote divides and eventually forms a blastocyst that is implanted in the uterus.
k.Placenta:
An organ or a structure that connects the maternal and foetal blood is called placenta. The growing foetus receives its nourishment, oxygen through the placenta.
The process by which an organism produces its offsprings is called reproduction.
Types of reproduction:
Reproduction can be further classified into two types:
a. Sexual reproduction -The type of reproduction which involves two parents and fusion of gametes is called sexual reproduction . For example,reproduction in Human beings
b. Asexual reproduction - This type of reproduction does not involve two parents and fusion of gametes. Here the offspring produced are identical to the parents and are referred to as clones. For example - Amoeba reproduces by binary fission, wherein an Amoeba divides itself into two daughter cells. This process does not involve fusion of gametes.
Sexual reproduction in human being :
In the fallopian tube present in the female reproductive system, the male gamete (sperm) fuses with female gamete (ovum) and gives rise to zygote. This process is called fertilisation. The zygote further develops into a multicellular human. Thus human beings reproduce sexually.
b.Introduction:
There are five classes under phylum chordata - fish, amphibians, reptiles, mammals and birds. Members of these classes that reproduce sexually, either give birth to young ones directly (viviparous) or lay eggs (oviparous) or in some cases the egg hatches within the organism and it gives birth to young one (ovoviviparous).
Oviparous:
Sexually reproducing organisms that lay eggs and the development of the zygote occurs within the egg. Such organisms are called oviparous.
Eg : Birds
Viviparous:
Sexually reproducing organisms like humans, that give birth to young ones directly. In this case the development of the zygote occurs within the body of the organism. Such organisms are called viviparous.
Ovoviviparous:
In some sexually reproducing organisms the egg hatches within the organism and gives birth to young ones. Such organisms are called ovoviviparous. Example- sharks.
c.Fertilisation:
The process of fusion of male and female gamete that gives rise to unicellular zygote is called fertilization.
Types of fertilisation :
Based on where the fertilisation occurs, it can be classified into two types -
a. Internal fertilisation - fusion of male and female gametes occurs within the body. Example - human
b. External fertilisation - fusion of male and female gametes occurs outside the body. Example- frog
Fertilisation in Human:
In human beings, the male gamete (sperms) is transferred to the female reproductive system. The sperm fuses with the ovum at the ampulla in the fallopian tube of the human female reproductive system.
Thus fertilisation in humans is internal.
d.Ploidy:
Total number of set of chromosomes present in a cell is called ploidy.It is represented by n.
Diploid:
If a cell has two sets of chromosomes it is called diploid. It is represented by 2n.
For example, in humans, the body cells have two sets of chromosomes. Each set has 23 chromosomes in it.
Haploid:
If the ploidy of the cell is half its original number, it is called haploid. For example,in humans, the male and female gametes are produced by meiosis. Thus the chromosome content in these cells are half of the other body cells. Thus gametes are haploid cells.
e.Fertilisation:
The fusion of male and female gametes is called fertilisation. Zygote is the product formed as a result of fertilisation.
Ploidy of zygote:
The gametes are formed as a result of meiosis. Thus the number of chromosomes is half of the number of chromosomes in the somatic cells. Therefore gametes are haploid.
Since zygote is formed due to the fusion of two haploid gametes, it is diploid. Which implies zygote has two sets of chromosomes, one set from each parent.
f.Formation of Ovum:
Ovary is the female gonad that produces the ovum. The process of formation of ovum is called oogenesis. This process occurs in multiple steps. The ovary consists of multiple cells called the follicles. Eventually these follicles form a mature follicle called the graafian follicle, that consists of the ovum.
Ovulation:
When the concentration of luteinizing hormone reaches its peak, the graafian follicle ruptures and releases the ovum.The process of release of ovum from a mature follicle is called ovulation.
g.Ovulation:
The process of release of ovum from a mature follicle is called ovulation. The process of formation of mature ovum is called oogenesis. From oogenesis to ovulation, all the processes are regulated by different hormones.
FSH and LH are the two pituitary hormones that are involved in regulating oogenesis and ovulation respectively.
When the LH levels reach their peak, ovulation occurs.
h.Fertilisation:
The fusion of male and female gamete which are haploid cells gives rise to a diploid, unicellular cell called the zygote. The zygote further develops into an embryo and eventually gives rise to an organism.
i.Fertilisation:
The process of fusion of male and female gametes is called fertilisation. This occurs in sexually reproducing organisms.
Types of fertilisation:
Based on where the fertilisation occurs, it can be classified into two types:
a. Internal fertilisation - fusion of male and female gametes occurs within the body. Example - human.
b. External fertilisation - fusion of male and female gametes occurs outside the body. Example- frog.
Fertilisation in human:
In human beings, the male gamete (sperms) is transferred to the female reproductive system. Then the sperm fuses with the ovum at the ampulla in the fallopian tube of the human female.
Thus fertilisation in human is internal.
j.Introduction:
The zygote is a unicellular diploid cell that undergoes cleavage as it travels from the site of fertilisation in the fallopian tube to the uterus. Cleavage is a type of cell division wherein the cell does not increase in mass,but it divides to form multiple smaller cells within one large single cell. These smaller cells are called blastomeres.
Development of zygote:
The zygote undergoes cleavage and give rise to 2 celled stage, 4 celled stage, 8 celled stage and 16 celled stage. Once it reaches the 16 celled stage, the blastomeres rearrange as outer trophoblast and inner cell mass. During this stage a cavity called blastocoel develops. The structure thus formed is called blastocyst. This blastocyst embeds in the endometrial lining of the uterus giving rise to the embryo. This process is called implantation
Thus the zygote divides and eventually forms a blastocyst that is implanted in the uterus.
k.Placenta:
An organ or a structure that connects the maternal and foetal blood is called placenta. The growing foetus receives its nourishment, oxygen through the placenta.
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