GENE REGULATION-

All the biochemical reactions are controlled by enzymes. The synthesis of enzymes is controlled by genes. Whenever the cell needs a particular enzyme, the gene that controls a particular enzyme will be switched on. Then only the cell needed enzyme will be synthesized. If cell does need a particular enzyme, the gene that controls the synthesis of a particular enzyme will be switched off.

GENE EXPRESSION

The characters in an organism are controlled by genes. The genes lie in chromosomes. Each chromosome contains one molecule of hereditary material called D.N.A. So, the gene contains a part of D.N.A. Every biochemical reaction needs an enzyme. The enzymes are the proteins and are synthesized on ribosomes. All the enzymes information lies in D.N.A.

GENE-EXPRESSION

BLOOD GROUP INHERITANCE

In the human beings, the character blood group contains '4' Phenotypes. These are A, B, AB and O. These are first discovered by Landsteiner.

BLOOD GROUP INHERITANCE

SEX LIMITED TRAITS

1.DEFINITION :The characters that are physically expressed in one sex only are called sex limited traits. But both the sexes contain genes.

Sex limited genes are active in presence of hormones.

2.SEX LIMITED TRAITS-EXAMPLES

These are autosomal traits. The secondary sexual characters like beared in male human beings. The beard controlling gene is active in presence of androgens (male hormones ). In female human beings, beard is absent due to the absence of androgens.

Milk secretion genes are present in both the sexes. But milk is secreted from female mammals only.

SEX INFLUENCED TRAITS

DEFINITION:The traits that are dominant in males and recessive in females are called sex influenced traits.

These are autosomal traits. The sex influenced traits are exhibited in both the sexes. But these are dominant in males and recessive in females.

EXAMPLES

i. Baldness in human beings . Hair on head is character. The two contrasting forms are full hair and Bald hair. Baldness controlling gene 'B+' is dominant in male human being over full hair gene 'B-'. But in female human being, Bald ness gene 'B+' is recessive to full hair gene 'B-'. So one B+ gene is enough to cause baldness in males. Where as two baldness genes are required to cause baldness in female.

baldness

SEX LINKED INHERITANCE

 

The characters are controlled by genes. The genes are inherited through the chromosomes. The SEX LINKED INHERITANCEchromosomes are two types. These are autosomes and sex chromosomes. The autosomes are identical in both male and female organisms. But sex chromosomes which determinate sex are different in male and females.

The genes that lie on sex chromosomes are called sex linked genes. The traits that are controlled by the genes of sex chromosomes are called sex linked traits.

SEX DETERMINATION

The living organisms are two types. They are bisexual or monoecious and unisexual or dioecious. Bisexual organism contains both testis and ovary. The same tissue in bisexual organism is able to produce sperms in testis and ova in ovary. In dioecious organsims, the male and female gametes are produced by seperate individuals. The question of sex determination arises in unisexual organisms only.

SEX DETERMINATION

CARINATAE-FLYING BIRDS CHARACTERS

AVES-INTRODUCTION

Aves are bipedal, warm blooded vertebrates with an exoskeleton of epidermal feathers and scales. Body temperature is very high and constant in birds. clip_image001Birds resemble reptiles in many characters such as laying of eggs on land and formation of foetal membranes during embryonic development. Due to these common features, reptiles and birds are included in the group Sauropsida Based on the resemblances between the fossil birds and the reptiles, Huxley described birds as the glorified reptiles".

CHARACTERS OF FLIGHTLESS BIRDS (PALAEOGNATHAE –OR- RATITAE)

CHARACTERS OF FLIGHTLESS BIRDS (PALAEOGNATHAE –OR- RATITAE)
1. Flightless birds are included in this group.
2. They are usually large birds adapted for running or walking.
 
3. Two to Four toes are present in their legs. For example two toes in African ostrich, 3 toes in American ostrich and Emu and 4 digits in kiwi.
4. Wings are reduced or absent. Feathers bear barbs. Barbules and barbicels are absent.
5. Tail feathers and oil gland absent.
6. Flight muscles are very much reduced.

EUTHERIA – METATHERIA-PROTOTHERIA-CHARACTERS

DISTINCTIVE FEATURES OF PROTOTHERIA

1. The prototheria are described as primitive unfinished mammals by Romer.

2. The mammary glands of prototheria are modified swear glands unlike the Eutheria. Teatless mammary glands are characteristic of prototheria.

3. Males possess functional mammary glands. The feeding of young with milk by father and mother (parents) 'is known as gynaecomastism.

prototheria-duckbill-ornithorhynchus

MAMMALS-CHARACTERS

 Mammals (Gr: mammae = mammary glands) are highly evolved tetrapods and they are at the top of the animal kingdom. They were originated in Jurassic period about 180 million years ago from mammal like reptiles, the therapsids (extinctcotylosaurian reptiles).mammals
Various orders of mammals came into existence during the early part of Coenozoic era which is regarded as the Golden age of mammals Mammals are highly successful group of vertebrates. They are found in all parts of the world showing wide range of adaptive radiation.
The class Mammalia includes a variety of animals such as moles, rats, rabbits, bats, cats, whales, horses, camels, elephants, apes, monkeys, man etc. There are about 4000 species of mammals spread over in 27 living orders. Parental care, social behaviour are well developed in the class, Mammalia.

MECHANISM OF SNAKE BITE-TREATMENT

 

Snake-Poisonous Apparatus Structure:

The poison apparatus of snakes consists of a pair of poison glands, their ducts and a pair of fangs. In poisonous snakes the poison glands are situated one on either side of the upper jaw. The poison glands are possibly the superior labial glands or parotid glands. Each poison gland is sac-like and provided with a narrow duct at its anterior end. The duct passes forward along the side of the upper jaw and loops over itself just in front of the fang and opens either at the base of the fang or at the base of the tunnel on the fang. The poison gland is held in position by ligaments. An anterior ligament attaches the anterior end of the gland to the maxilla. A posterior ligament extends between the gland and the quadrate. Fan-shaped ligaments are situated between the side walls and squamoso-quadrate junction. The fangs are sharply pointed and are enlarged maxillary teeth. The fangs regenerate when lost.MECHANISM OF SNAKE BITE

Fangs are of two types

IDENTIFICATION OF POISONOUS SNAKES AND NON-POISONOUS SNAKES

DIFFERENCE BETWEEN VENOMOUS AND NON-VENOMOUS SNAKES

Most of the snakes are non-poisonous. Identification of poisonous or non-poisonous snakes is important because sometimes the bite of a non-poisonous snake may lead to death out of fear. The poisonous snakes possess certain characteristics by which it is possible to distinguish them from non-poisonous snakes.

The poisonous snakes are identified by a careful examination of the following points.

1.Nature Of The Tail,

2.Natureof The Ventrals,

3.Nature Of The Scales On The Head,

4.Nature Of The Sub-Caudal Scales,

5.Nature Of Vertebrals.

1.From The Nature Of The Tail

The tail of a snake should be observed first.



If the tail of a snake is flat, laterally compressed and oar-shaped (adaptation to swimming in water), it is a sea snake. All sea snakes are poisonous. The body is covered by small scales dorsally.Eg: Hydrophis, Enhydrina.

If the tail ends bluntly, it is non poisonous.

If the tail is round orcylindrical and pointed, it may be poisonous or non-poisonous. It may be terrestrial or fresh water.

IDENTIFICATION OF  SNAKES  NON-POISONOUS tail

NON-POISONOUS SNAKES

NON-VENOMOUS SNAKES

This topic  detail discuss about different non poisonous snakes and their characters.The previous topic is about different types of poisonous snakes

Typhlops (Blind snake)

1. It is a worm-like snake of about 15 to 30 cms. It lives underground and looks like an earthworm. Eyes are small, covered with scales, so it is almost blind. It is commonly known as blind snake. It is insectivorous, feeding chiefly on termites.Typhlops (Blind snake)

 

 

 

 

 

 

 

 

POISONOUS SNAKES

VENOMOUS SNAKES TYPES

SEA SNAKES

1. All sea snakes are poisonous. These are the most venomous of all snakes.

2. They are identified by the laterally compressed (oar-shape tails.SEASNAKES-hydrophis

 

 

 

 

 

 

 

 

3. The belly plates are small and not broad. Eyes and fangs are small.