Animal Tissues

Body of a multicellular animal is formed of many cells. Group of cells similar in structure , function and origin form a "Tissue". Branch of Biology that deals with the study of tissues is known as 'Histology'. Animal cells have narrow space around them which contains fluid called as Extra cellular fluid/ Intercellular fluid. ORIGIN OF TISSUES: All tissues originate from the cells of any of the three germ layers - ectoderm, mesoderm and endoderm. TYPES OF TISSUES: 4 major types of tissues are there- Epithelial tissues, Connective tissues, Muscular Tissue and Nervous Tissue. 1.1. Epithelial Tissues : ( Gr. Epi - Upon thele - nipple) Epithelial tissues are the tissues composed of one or more layers of cells covering the external surface of the body and internal organs or lining the cavities in the body and viscera There are no blood vessels supplying nourishment to these tissues but they receive nutrients from underlying connective tissues. Structure: These tissues consist of variously shaped cells arranged closely in one /more layers. There is little intercellular material between the cells and cells are held together by intercellular junctions. Epithelia rests on a thin basement membrane which is made up of Glycoproteins and collagen fibres. Types: On the basis of arrangement and shape of cells, the epithelia are classified into two groups:- Covering & Glandular Epithelia

MORPHOLOGY

Morphology is the study of general appearance and structure of an organism or its parts. External Morphology deals with external features of an organism without dissecting it. Internal Morphology deals with internal structure of an organism seen after dissecting it. Animals are grouped as chordates and non - chordates. Earthworm & Cockroach are non - chordates. Frog and Rat are chordates. 1.1 EARTHWORM:-  Earthworms belong to phylum Annelida, Genus - Pheretima and species - Posthuma. There are about 500 sps. out of which 13 are found in India (a) Habitat:- These are found in moist soil, living in upper layer to a depth of about 30 - 45 cm In dry climate, they come out on the ground (b) Habit:- These are nocturnal, feed upon decaying organic matter in the soil, leave their faecal deposit as 'Warm Castings', dig their burrows and move by muscular contractions. (c) External morphology:-  Shape:- Cylinderical, elongated, pointed arteriorly and slightly rounded posteriorly. Size:- full grown worm is about 150 mm long and 3 - 5 mm wide Colour:- Reddish brown. Dorsal surface is darker than ventral surface and has a dark median line Segmentation:- Entire body has 100 - 120 segments / metameres Externally the segments are separated / divided by annuli & internally by Septa. Each annuli corresponds to a septa except the first four. This type of segmentation, which is both, external and internal is called 'Metameric Segmentation' or 'Metamerism'. Mouth:- It is present at the anterior end of first segment 'Peristomium'. A small fleshy 'Prostomium' hangs over mouth. Anus:- It is slit like opening in the last segment 'Anal segment' (Pygidium). Female genital pore:- It is a small opening on ventral side of 14th segment. Eggs pass out of this Male genital pores:- A pair of openings present on ventral side of 18th segment. Male reproductive fluid and sperms come out of this. Nephridiopores:- These are numerous, very fine openings of excretory organs, scattered irregularly over all the segments except the first two. Clitellum:- A band of glandular skin called 'clitellum' covers the segments 14, 15, 16. It secretes mucus and albumen which helps in fertilization. On the basis of clitellum, body of earthworm is divisible into preclitellar, clitellar and post - clitellar regions Setae:- In all the segments, except first, last and clitellum, there is a ring of s - shaped setae which are made of chitin. These help in holding the substratum and during copulation.

Internal Structure of Angiospermous Plants

The plant body is made up of cells which organize themselves to form Tissues. Tissues organize to form tissue system. The study of the internal structure of plants is known 'Plant Anatomy'. 1.1 Tissue: -It is a group of similar or dissimilar cells performing a common function and having a common origin. Types of tissues:-Two types -Meristematic and Permanent. 1. Meristematic Tissues(Meristems): -These are a group of cells which are in a continous state of division. These tissues divide to form new cells which differentiate to give rise to permanent tissues. Types of meristems: -  A. On the basis of origin & development, these are of three types:  i. Promeristem: -It is a group of initial cells that lay down the foundation of an organ or plant part. ii. Primary meristem: -It is formed from promeristem. Primary body, tissue differentiation and their organization' results from activity of primary meristem. iii. Secondary meristem: -These are formed secondarily from permanent tissues which acquire the power of division. B. Depending on their position in plant body, these are of three types: i. Apical meristem: -Present at the tips of stem, root and their branches. Responsible for growth in length. It is dome like with outer layer-Tunica& inner mass-Corpus. It has promeristem which differentiates into three regions: - * Dermatogen: -Outermost layer; gives rise to epidermis of the stem. In roots, it forms 'Calyptrogen' which is a mass of tissues which forms root cap. In dicots-it forms epilema of roots. * Periblem: -next to dermatogen. Forms cortex of root and stem. * Plerome: -lies internal to periblem. Cells elongate here and form procambuim which later forms Xylem & Phloem. ii. Intercalary Meristem: -It is located in between the regions of permanent tissues. These cells divide and continue to add new cells. These are responsible for growth in length. Present at bases of node, internodes and leaves. iii. Lateral Meristem:-These occur on sides & increase the girth of plant.

CHROMOSOMAL BASIS OF INHERITANCE

In heredity, genes are transmitted from parents to the off springs. Certain principles of genetics are followed in this. Genes are located on chromosomes. So, the genetic material is transmitted from one generation to the other by chromosomes. This is inheritance on the basis of chromosomes. Sometimes genes present on same chromosome do not assort independently but remain linked together and pass on to next generation together. This is linkage. (1.1) PARALLELISM BETWEEN GENES AND CHROMOSOMES:- There is a perfect parallelism between genes & chromosomes which can be indicated by following facts:- 1 - Each species has a specific number of chromosomes in its somatic cell. In diploid cell, chromosomes occur in pairs (homologous pairs), one member of pair comes from paternal and other comes from maternal parent. Similarly genes also occur in pairs (Allelomorphic pair); genes in pair are contributed by both parents. 2 - During mitosis, the two chromatids of a chromosome separate into 2 daughter nuclei which later form 2 daughter cells. Similarly, each gene of allelomorphic pair goes into each daughter cell 3 - AT meiosis, chromosomes of each kind (homologous chromosome) separate. Similarly, genes of each kind also separate in meiosis 4 - Chromosomes unite & form a diploid pair after fertilization. Similarly, genes also form a pair after fertilization.

Inheritance

There are different life forms which may be similar at cellular level of organization but at organismal level, a lot of diversity can be seen. Members of a particular species resemble closely & have a set of similar characters by which they are identified. Genetics deals with the study of these characters how these are passed on from one generation to another (ie, parents to offsprings) (1.1) Inheritance: Heredity and Variation Genetics (GK. 'genesis'-descent) is the branch of biology that deals with the study of heredity and variations. The term 'Genetics' was coined by William Bateson in 1906. Offspring resemble their parents. This resemblances might not be 100% which means that difference among the members of a species can also be seen. These differences shown by individual of a species and also by offspring of same parent are called 'VARIATIONS'. The transmission of characters, resemblances and variations, from one generation to the next is called Heredity.

Understanding Life

INTRODUCTION:  Some organisms are living e.g. Bacteria, animals whereas some organisms are non-living. e.g. bricks ,stones. The main difference between the two is of ‘life’. Defining ‘life’ is difficult. Example of virus supports it. A virus doesn't have a life but when it is inside a cell, it becomes active and multiplies showing that it has life. (1.1) ORGANISMS SHARE SOME BASIC AND UNIFIED CHARACTERISTICS : Living organisms differ from each other in many aspects but they have many things in common like all are built up of cells, which have same structure and function. All have same basic characteristics governed by same physical laws like order, energy utilization, regulation, growth, development, reproduction etc. Common feature of living organisms: * Have fixed shape and size. * Are highly organized. It is because of this organization that living being is called ‘organism’. Cell is the basic structure of organization and there are different levels of organization. * All show metabolism i.e. series of biochemical reactions keep going inside cell. Reactions involving breakdown of compounds are ‘catabolic reactions. Reactions involving synthesis of compounds are ‘anabolic reactions’. * Use energy for metabolism and growth. * Show development and reproduce. * Maintain constant body temperature (Homeostasis) * Adapt to environmental changes. * Gradually evolve into new species.

SYSTEMATIC

There are more than 10 million kinds of living organisms like animals, plants, bacteria, viruses which are different from one another. Out of these, nearly 1.2 million animals and 0.5 million plant species have been studied. Many are still unknown. To study and remember each species is practically not possible. So, to make this simpler, Biologists name them. They use techniques for identifying, naming and grouping of organisms. (1.1) BIOLOGICAL CLASSIFICATION: -- To pick an organism of known characters from a huge variety of living organisms is not possible. They must be divided into groups and sub-groups with each having organisms of almost similar characters. Definition- The scientific ordering of organisms in hierarchical series of groups/ sub-groups on the basis of similarities/ differences and their relationships is called Biological Classification. Objectives of biological classification -: 1.to organize vast number of animals and plants into categories and then naming them. 2. To recognize basic unit of classification i.e. Species. Advantages of Biological classification: - 1.It makes identification and study of organisms convenient. 2. It shows relationships among various groups of organisms. 3. It shows evolutionary trend. 4. Study of a representative from each group gives a broad idea about whole group. 5. It helps in study of fossils for finding evolutionary relationships. Systematics/ Taxonomy (Gk.words) Systema-order. (taxis-arrangement nomos-law) Given by de Candolle in 1813. Deals with the identification, nomenclature and classification of organisms. Some scientists consider Systematics and Taxonomy as separate fields. According to G. Simpson (1961), Systematics is the study of diversity of organisms and all their comparative and evolutionary relationships based on comparative anatomy, ecology, physiology and Biochemistry. Whereas Taxonomy is the study of principles and procedures of classification. And Classification is the sub-topic of systematics dealing with ordering of organisms into groups. But all these terms are inter-related and so inter-changeable also.