B.Sc.(Hons.) in Zoology

🔰Revision Notes on Human Reproduction🔰

(1) Reproduction is the formation of new individuals of their own kind by living organisms.
(2) The Male Reproductive System consists of:
(a) Primary sex organs i.e. a pair of testes suspended in a scrotum.
(b) Secondary sorgans i.e. a pair of ducts each differentiated into an epididymis, a vas deferens and an ejaculatory duct.
(c) A male urethra passing through an erectile penis.
(d) Three types of Glands - a pair of seminal vesicles, a prostate gland and a pair of Cowper’s glands.

(3) The Female Reproductive system consists of:
(a) Primary sex organ i.e. a pair of ovaries
(b) Secondary sex organs i.e. a pair of fallopian tubes (oviducts) , a uterus (womb), a vagina.

(4)Ovaries produce female gametes called ova.


🔷Phases of embryonic development
Embryonic development involves following dynamic changes and identifiable process.

(1) Gametogenesis : It involve the formation of haploid sex cells or gametes called sperms and ova from diploid primary germ cells called gametogonia present in the reproductive organs called gonads (testes and ovary). It is of two types;

(i) Spermatogenesis: Formation of sperm.
(ii) Oogenesis : Formation of ova

(2) Fertilization: It involves the fusion of haploid male and female gametes to form diploid zygote. The fusion of gametic pronuclei is called Karyogamy while the mixing of two sets of chromosomes of two gametes is called amphimixis.

(3) Cleavage: It includes the rapid mitotic division of the zygote to form a single layered hollow spherical larva called blastula and its formation is called blastulation.

(4) Implantation: The process of attachment of the blastocyst (mammalian blastula) on the endometrium of the uterus is called implantation.

(5) Gastrulation: It includes the mass and orderly migration of the organ specific areas from the surface of blastula to their predetermined position which finally produces a 3 layered gastrula larva. It is with 3 primary layers.

(6) Organogenesis: It includes the formation of specific organs system from three primary germ layers of gastrula and also includes the morphogenesis and differentiation.

🔷Fertilization
(1) Definition: Fusion of a haploid male gamete (spermatozoon) and a haploid female gamete (ovum) to form a diploid cell, the zygote, is called fertilization or syngamy.

(2) Site of fertilization: Fertilization in human female is internal as in other mammals. It takes place usually in the ampulla of the fallopian tube.

(3) Steps of fertilization
(i) Approach of sperm to ovum:
(a) Male discharges semen (3.5 ml) in the female’s vagina close to the cervix during coitus. This is called ejaculation or insemination. This ejaculation contains as many as 400 million sperms but only about 100 sperms reach the fallopian tube because many sperms are either killed by the acidity of female genital tract or engulfed by the phagocytes of the vaginal epithelium.
(b) The sperm swim in the seminal fluid at the rate of 1-4 mm per minute by the aspiratory action of the uterus and peristaltic movement of the fallopian tube.
(c) Capacitation is the phenomenon of physiological maturation of sperms by breaking of acrosome membrane inside the female genital tract. It takes about 5-6 hours.
(d) Ovum is released on the 14th day of menestrual cycle trapped by the fimbriae of the ampulla of fallopian tube and move towards the uterus by peristalsis and ciliary action.
(e) At the time of ovulation, egg is at secondary oocyte stage.
(f) Fertilizability of human sperm in the female genital tract is of 12 to 24 hours while its survival value is upto 3 days and of ovum is only 24 hours though it can live for about 72 hours.

♻️Important Cells in NCERT Biology

1. Heterocysts: Specialised cells found in Nostoc & Anabaena which help in fixation of atmospheric nitrogen.
2. Smallest living cell is Mycoplasma
3. Choanocytes or collar cells - Found in sponges that line the spongocoel & canals.
4. Cnidoblasts/cnidocytes - Found in Coelenterata/cnidaria which contains the stinging capsules or nematocytes.
5. Flame cells- Found in flatworms and help in osmoregulation & excretion.
6. Statocysts- These are balancing organs found in arthropods.
7. Root hair- Found in the zone of maturation and help in water & mineral absorption
8. Guard cell- Encloses stomatal aperture or pore. Bean-shaped but in grasses dumb-bell shaped.
9. Subsidiary cells- A few epidermal cells, in the vicinity of the guard
cells become specialised in their shape & size & called subsidiary cells
10. Bundle-sheath cells- The vascular bundles are surrounded by a layer of thick-walled bundle-sheath cells.

Functions of Leaves:-

The leaves have many primary and secondary functions.

Primary Functions:-

(a) The most important function of leaves is photosynthesis with the help of sunlight and carbon dioxide.

(b) Leaves contain stomata through, which gaseous exchange occurs.

(c) Leaves are the site of transpiration.

(d) They protect axillary and terminal bud from mechanical injury and desiccation.

Secondary Functions:-

(a) Leaves store food as in the leaf base, e.g., Onion.

(b) Leaves change into phyilodes to protect against transpiration.

(c) Storage of water in the cells of some succulent plants, e.g., Aloe.

(d) In Salvinia, one leaf of each node is changed into roots that act as balancer for floating.

(e) In some leaves like of Euphorbia, the young leaves are brightly coloured to attract insects for pollination.

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👀Revision Notes on Human Health and Disease


Types of Diseases
The diseases may be broadly classified into two types: Congenital and acquired.

(i) Congenital Diseases: These are anatomical or physiological abnormalities present from birth. They may be caused by (i) a single gene mutation (alkaptonuria, phenylketonuria, albinism, sickle-cell anaemia, haemophilia, colour blindness); (ii) chromosomal aberrations (Down’s syndrome, Klinefelter’s syndrome, Turner’s syndrome); or (iii) environmental factors (cleft palate, harelip). Unlike the gene-and chromosome-induced congenital defects, environmentally caused abnormalities are not transmitted to the children.

(ii) Acquired Diseases: These diseases develop after birth. They are further of two types: communicable and non-communicable.

(a) Communicable (Infectious) Diseases: These diseases are caused by viruses, rickettsias, bacteria, fungi, protozoans and worms.

(b) Noncommunicable (Noninfectious) Diseases: These diseases remain confined to the person who develops them and do not spread to others. The non-communicable diseases are of four kinds –

(1) Organic or Degenerative Diseases: These diseases are due to malfunctioning of some of the important organs, e.g, heart diseases, epilepsy. Heart diseases result from the abnormal working of some part of this vital organ. Epilepsy may result from abnormal pressure on regions of the brain.

(2) Deficiency Diseases : These diseases are produced by deficiency of nutrients, minerals, vitamins, and hormones, e.g., kwashiorkor, beriberi, goitre, diabetes are just a few from a long list.

(3) Allergies: These diseases are caused when the body, which has become hypersensitive to certain foreign substance, comes in contact with that substance. Hay fever is an allergic disease.

(4) Cancer: This is caused by a uncontrolled growth of certain tissues in the body.


👉🏻The Immune System
(1) Immunity – The ability of the body to protect against all types of foreign bodies like bacteria, virus, toxic substances etc. which enter the body.

(2) The science dealing with the various phenomena of immunity, induced sensitivity and allergy is called immunology.

(3) Immune Response - Third line of defence. Involve production of antibodies and generation of specialized lymphocytes against specific antigens.

(4) Antigens – Substances which stimulate the production of antibodies, when introduced into the body.

(5) Antibodies – Immunoglobulins (Igs) which are produced in the body in response to the antigen or foreign bodies.

(6) All antibodies are immunoglobulins but all immunoglobulins are not antibodies.

(7) There are two major types of immunity: Innate or Natural or Non-specific immunity and Acquired or Adaptive or Specific Immunity.


👉🏻Malaria:
Malaria has been for thousands of years a very serious disease of the tropical and temperate regions. It was almost eliminated a few years back with the efforts of World Health Organization (WHO) and our National Malaria Eradication Programme (NMEP), but unfortunately, it has appeared again.

(a) Symptoms: The attack of malaria is preceded by yawning, tiredness, headache and muscular pain. During the fever, the patient feels chilly and shivers, and has acute headache, nausea and high temperature. After a few hours, the body perspires freely and the temperature becomes normal. The cycle is repeated if no medicine is taken. Blood smear made during fever shows the malarial parasites. No parasites are seen at other times. In chronic cases, there is general weakness and anaemia (paleness) due to large-scale destruction of red blood corpuscles. This is also accompanied by enlargement of spleen and liver.

(b) Cause: Malaria is caused by the toxins produced in the human body by the malarial parasites, Plasmodium.

Terminology

1. Genetics: The branch of biology concerned with the study of heredity and variation

2. Eugenics: The application of principles of genetics for the
improvement of human kind.

3. Gene pool: The sum total of all the alleles present in the breeding or reproductive members of a random mating population.

4. Gene frequency: The proportion of one allele relative to all the alleles of a gene in a Mendelian population.

5. Cytogenetics: Concerns with the study of various aspects of
chromosomes and their effects on the development of characters of organisms

6. Genome: A complete set of chromosomes of a diploid species

7. The first artificial hybrids in plants were produced by Thomas Fairchild in 1717 when he crossed sweet William with carnation.

8. Euphenics: Deals with the control of hereditary diseases
especially inborn errors of metabolism.

9. Epistasis: When one gene affects in any way the expression of another gene, the phenomenon is called epistasis.

10. Genomics: It refers to the study of the structure and function of entire genome of an organism.

11. Biodiversity: Refers to the total variability present within and among species of all living organisms and their habits

12. Acclimatization: Refers to adaptation or adjustment of an
introduced variety to the new environment.

13. A -line: Means the male sterile parent used in crossing to develop a new hybrid seed. it is the male sterile line.

14. B -line: It is the fertile counter parent of the 'A' line, it is also called the maintainer line.

15. R -line: It is an inbred line which when crossed with a male sterile strain, the resultant hybrid is male fertile.

16. In vitro: biochemical process taking place in a test tubes (in lab.)