Tissues Level

In multicellular animals and plants, groups of similar cells are organized into loose sheets or bundles, performing similar functions. These are called tissues. Each tissue has a particular function in the life of the organism, e.g. muscle tissues, glandular tissues, xylem tissues, phloem tissues, etc. They are specialized for contraction (movement), secretions, conducting, water, and translocation of sugar, protein, etc.

The class

Organ and system

Different tissues having related functions assemble together in a structure to carry out its function with great efficiency. Such structures are called organs, and they are specialized to perform particular functions. For example, stomach, which is an organ, has a function of food, digestion, protein, but has a secretory epithelium, which secretes the gastric juice and muscular tissues, tissues smooth for conducting the valve of the stomach and mixing the food with the enzyme thoroughly and moving the food to the posterior end. The formation of organs also has a selective value because this leads to an efficient accomplishment of their function, both quantitatively and qualitatively. In animal organs, formation is far more complex and defined. Organs are part of organ system where total functions involved in one process or phenomenon are carried out.

The second level of organization is much less defined, definite in plant than it is in animal. At the most, we might distinguish roots, stems, leaves, and reproductive structures, clear-cut functions. The distinguishing features can be assigned to each of these structures.

Are involved in ensuring the plant storage of food and producing water and minerals. In shoot supporting the entire plant while the leaves are primary organ for food manufacture. Flower or other reproductive structures are involved in producing the next generation reproduction.

The complexity of the organ system of animal is associated with far greater range of functions and activities than is found in plant.

Individual, whole organism

Various organs in plant and various organ system in animal are assembled together in form an individual, the whole organism. The whole organism has its individuality as far as its characteristics are concerned.

It is different from other members of the same species in certain respects. The various functions, processes, and activities of an organism are coordinated. In animal all the systems work in coordination with each other. For instance, if a man is engaged in continuous and hard exercise, not only his muscles are working, but there is an increase in the rate of respiration and heartbeat to supply the muscles with increased oxygen and food which they need for continuous exercise.

In animals, the coordination is achieved by means of the nervous system and endocrine system, whereas in plants, only long-term regulation of activities is brought about by hormones.

Organisms work as a whole and it interact and respond to environmental change as a whole.

Population

A population is a group of living organisms of the same species located in the same place at the same time. Examples are the number of rats in a field of rice, the number of students in your biology class, or the human population in a city.

Population is a higher level of biological organization than an organism (whole) because here a group of organisms of the same species is involved. This level of organization has its own attributes, which come into being by living together of a group of organisms of the same species.

Some of these attributes are gene frequency, gene flow, age distribution, population density, Population pressure, etc. All these are new parameters that have appeared due to the population of an organism. You will study them in detail in Population Ecology.

Population of different species (plants and animals) living in the same habitat forms a community. Communities are dynamic collections of organisms in which one population may increase and another may decrease. Due to fluctuation in habitat factors, some communities are complex and well interrelated; other communities may be simple. In a simple community, any change can have a drastic and long-lasting effects.

The foregoing accounts make it clear that an organism can be studied at different levels of organization. It can be studied at the subatomic, atomic-molecular, macromolecular, organelle-cell-tissue, organ, and organ-system levels.

We can also look at it as an individual, as a part of a population of similar individuals, as a part of a community that includes other populations, and as a part of a community of an ecosystem, which includes abiotic factors as well as living organisms.

The foregoing accounts make it clear that an organism can be studied at different levels of organization. It can be studied at the subatomic, atomic-molecular, macromolecular, organelle, cell-tissue, organ, and organ system level. We can also look at it as an individual, as a part of a population of similar individuals, as a part of a community that includes other populations, and as a part of a community of an ecosystem, which includes abiotic factors as well as living organisms.

The organism’s interaction can change, take many shapes. It may be predation, parasitism, commensalism, mutualism, and competition.

The world of today is enormous in size. It has been reproducing and evolving since the time of its origin. Today, almost all parts of the world are mutants in living organisms. The distribution of organisms in space can be studied through biomes.

Biome is a large regional community primarily determined by climate. It has been found that major types of plants determines the other kind of plants and animals. These biomes have therefore been named after the type of major plants and major features of ecosystem.

Living World in Time Since the time of origin of life on this planet, various organisms are involved and dominated this planet during various periods of geological time chart. This has been found by the evidence obtained from the discovery and study of fossils, which allows biologists to place organisms in a time sequence.

As geological time passes, a new layer of sediments is laid down, and the older organisms should be deeper layer, provided the sequence of the layers has not been disturbed. In additional, it is possible to date/age rocks by comparing the amounts of certain radioactive isotopes they contain. The older sediment layer has less of these specific radioactive isotopes than the younger layers.  A comparison of the layers gives an indication of the relative age of the fossils found in the rocks. Therefore, the fossils found in the same layer must have been alive during the same geological period.