How the Living Organisms interact with the Environment

Living organisms and the physical environment have a close relationship. They interact with each other. The biosphere is the parts of Earth inhabited by living organisms. The biosphere consists of specific geographical areas known as biomes. A biome is a collection of different types of ecosystems. The ecosystems include grasslands, rain forests, streams, lakes, sea, deserts etc., with various types of organisms starting from bacteria, fungi, algae, and various other types of plants and animals. There are millions of known species of organisms and there are many millions to be discovered. Each organism lives in a specialized regional environment within the ecosystem known as the habitat. An organism can live in a specific habitat because it is adapted to live in that habitat. Deep-sea vent, bottom of sea, arctic rivers, and river banks, etc. are examples of habitat.

Organisms living in a specific environment interact with the environment and also with themselves in very different ways. There are big trees growing along the bank of the stream. Since the trees are very big, they make half of the stream a shady area, and this may make the temperature of the water a bit lower than that in the middle region. It is because the water at the bank side is not directly heated by the sun. Similarly, there are many algae floating in the water freely, and this may reduce the penetration of sunlight. So the light intensity under the water may be decreased. All the organisms living in an environment along with that physical environment form an ecosystem. The organisms living in a fresh water pond, along with the pond, form an aquatic ecosystem. All organisms on land along with their environment form the terrestrial ecosystem.

The energy flow in an ecosystem obeys the laws of thermodynamics. It is an open system. An open System allows the free flow or exchange of energy and matter such as water, carbon dioxide, nitrogen, food materials, and even the movement of organisms from one ecosystem to another. There are producers, consumers, and decomposers in ecosystems. The producers are the photosynthetic organisms or the autotrophs. The producers of the ecosystem take energy from sunlight and convert it into chemical energy. This energy is passed on to consumers and then to decomposers, which cycles back the materials to the environment. But the energy flows only in one direction and is not cycled back. Herbivorous animals consume the organic food synthesized by the producers, which form the primary consumers.

These herbivores form the food of carnivores, which are the secondary consumers. And finally the decomposers act on the dead remains of all these organisms including the producers. decompose the organic materials into inorganic materials, and thus cycle back the materials to the environment. This forms the food chain in the ecosystem. In each step of the food chain energy is also transferred. In each step a portion of the energy is lost in the form of heat. Thus, heat is flowing in one direction and is not cycled back. The energy enters the ecosystem from the sun through producers and leaves the ecosystem in all steps of the food chain in the form of metabolic heat.

The materials in the form of nutrients required for life are cycled between organisms and the environment. The materials are absorbed by the producers for synthesizing the nutrients and are cycled among the consumers and finally returned to the environment by the activity of saprophytes and other decomposers such as fungi and bacteria. Considering the flow of energy and nutrients in the ecosystem and in the biosphere, it can be considered a single living organism.

Tags: Bio Technology, Bio Genetics , Life Forms, organisms

Size & Complexity of Living Organisms

Living organisms greatly differ in size and complexity of their body. They range from minute unicellular bacteria to very big multicellular organisms such as blue whales and redwood trees. Primitive cell forms such as bacteria and blue-green algae are very simple in organization and function. The cells and organisms are very small and cannot be seen with the naked eye. A microscope is needed for observing these microorganisms. The multicellular organisms and their cells are very complex in organization and function. The body of higher plants and animals consists of billions of various types of specialized, structurally and functionally complex cells. Therefore, their body and its function is highly complicated.

Variations in the body size affect various other body measurements differently. This is because the volume of cells and so the volume of the entire organism increases much faster than the surface area. Entire single-celled organisms and most primitive multicellular organisms use their cell surfaces to acquire nutrients and dispose of wastes. But the amount of nutrients needed, and the quantity of wastes produced, is related to cell volume. Since the surface area to volume ratio of a cell decreases as its size increases, cells have an upper limit on how much volume they can sustain with a given surface area. Large organisms have less surface area relative to mass than do small organisms. This relationship affects the efficient exchange of material between the body and the environment. Allometric relationships describe the effect of body size on biological features. These relationships can reveal general patterns of how organisms function; for example, how much they sleep, their food requirements, and their brain size.


Allometric relationships also have practical applications, as in the proper determination of drug dosages for animals of differing body sizes. For multicellular organisms, increases in overall body size are mostly due to increases in cell number, not cell size. This is also because of surface area to volume ratio limitations on cells.

The evolution of complexity in multicellular organisms is driven by the specialization of cells. Multicellular complexity requires coordination among body cells. Internal communication mechanisms such as hormones and the nervous system help make this possible. Complexity also requires many body cells to give up reproduction in support of a relatively few cells that do reproduce.

Tags: Bio Technology, Bio Genetics , Life Forms, organisms

What are the Hierarchical Levels of Life Forms

Life on Earth is incredibly extensive and to make it easier to study, biologists have broken living systems up into generalized hierarchical levels as given below:

1) Molecules
2) Organelles
3) Cells
4) Tissues
5) Organs 6) Organisms
7) Populations
8) Communities
9) Ecosystems
10) Biosphere

The lowest level of the biological hierarchy begins with molecules. Examples include proteins, DNA, lipids, etc. Many such specialized molecules are organized into cells, the basic unit of life. There are single-celled organisms such as bacteria, amoeba, yeast, etc., in which the body consists of a single cell. When the body consists of more than one cell it is called multicellular. Multicellular organisms are collection of various types of specialized cells. A group of specialized cells carrying out a specific function is called a tissue. For example, muscle tissue, nervous tissue, connective tissue, etc. When different types of tissues are organized together to perform a common function it is called an organ. Examples include, liver, stomach, heart, etc. When a number of organs function together to accomplish a specific function of the body, it forms an organ system. For example, the stomach, liver, intestine, pancreas, salivary glands, etc. work together to form the digestive system. In an organism there are a number of organ systems that work in an associated way to form the organism and its life activities. Each individual organism is a member of a large population, which exists in a habitat.

A population is a group of organisms belonging to a species. A group of different species that live and interact in a particular area or environment is known as a community. The communities, along with the environment in which they exist, are known as ecosystems. An ecosystem consists of biomes, which are large geographical areas of the world. Each biome is a part of the biosphere, which includes the entire living population on the Earth along with its physical environment.

Tags: Bio Technology, Bio Genetics , Life Forms, organisms

Adaptation the special feature of Organisms

The existence of an organism in its environment or habitat is closely related to the special features of that organism or the adaptations. Adaptation is the special feature of an organism's morphology, anatomy, and physiology, which improves its interaction with its environment.


Adaptations usually have the following characteristics.
1) Special features are specially suited to a specific habitat.
2) These special features are often complex.
3) These special features help organisms to live in their environment and capture food, regulate the body's physiology, reproduce, disperse, and defend against enemies.

Adaptation is one of the important factors that drives the process of evolution. Adaptations are created through mutation and natural selection. Evolution requires genetic variation. In order for continuing evolution there must be mechanisms to increase or create genetic variation and mechanisms to decrease it. Mutation is a change in a gene. These changes are the source of new genetic variation. Natural selection operates on this variation. If these variations are suited to the changed environment that organism will outperform the others, which leads to the evolution of the population. If these new changes created through mutation are not suitable for existence in that environment, they will lead to extinction.Natural selection:Some types of organisms within a population leave more offspring than other Over time, the frequency of the more prolific type will increase. The difference ii reproductive capability is called natural selection. Natural selection is the only mechanism of adaptive evolution; it is defined as differential reproductive success of pre-existing classes of genetic variants in the gene pool.

The most common action of natural selection is to remove unfit variants as they arise via mutation. In other words, natural selection usually prevents new alleles from increasing in frequency. This led a famous evolutionist, George Williams, to say "Evolution proceeds in spite of natural selection."

Natural selection can maintain or deplete genetic variation depending on how it acts. When selection acts to weed out deleterious alleles, or causes an allele to sweep to fixation, it depletes genetic variation. When heterozygotes are more fit than either of the homozygotes, however, selection causes genetic variation to be maintained. (A heterozygote is an organism that has two different alleles at a locus; a homozygote is an organism that has two identical alleles at a locus.) This is called balancing selection. An example of this is the maintenance of sickle cell alleles in human populations subject to malaria. Variation at a single locus determines whether red blood cells are shaped normally or sickled. If a human has two alleles for sickle cell, he /she develops anemia-the shape of sickle cells precludes them from carrying normal levels of oxygen. However, heterozygotes who have one copy of the sickle cell allele coupled with one normal allele enjoy some resistance to malaria--the shape of sickle cells make it harder for the plasmodia (malariacausing agents) to enter the cell.


Thus, individual homozygous for the normal allele suffer more malaria than heterozygotes. Individual homozygous for the sickle cell are anemic. Heterozygotes have the highest fitness of these three types. Heterozygotes pass on both sickle cell and normal alleles to the next generation. Thus, neither allele can be eliminated from the gene pool. The sickle cell allele is at its highest frequency in regions of Africa, where malaria is most pervasive. Balancing selection involves opposing selection forces. An equilibrium results when two alleles selected in the homozygous state are retained because of the superiority of heterozygotes. Balancing selection is rare in natural populations.

Tags: Bio Technology, Bio Genetics , Adaptation of organisms