ENZYMES

ž  Enzymes are specific proteins which act as biological catalysts that speed up the rate of chemical reactions without undergoing any change themselves

  • ž  A catalyst is a substance which speeds up the rate of reactions without undergoing any chemical changes itself.
  • ž  The molecule on which an enzyme acts is called a substrate. The substrate binds with the active site of the enzyme.
  • ž  Active site is the part of the enzyme to which the substrate molecule attaches.
  • The substance formed as a result of enzyme action is the product.
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DEVELOPMENT OF ORGANISMS AND CONTINUITY OF LIFE (Sexual Reproduction in human)

Asexual Reproduction

Asexual reproduction is the production of genetically identical offspring from one parent.
Therefore asexual reproduction makes new organisms just like the parent. Hence they contain exactly the same genes. A population of organisms produced in this way, and all genetically identical, is known as a clone.
Asexual reproduction occurs in both plants and animals but mainly in simple organisms. Example: vegetative propagation in plants. This is a common natural process in which the part of a plant becomes detached from the parent plant and develops into new individuals. E.g. rose, straw berry, etc.

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RELATIONSHIPS OF ORGANISMS WITH ONE ANOTHER AND WITH THE ENVIRONMENT

ECOLOGY

OBJECTIVES:


* state that sun is the principal source of energy input to biological systems
* Describe the non cyclical nature of energy flow
* Define the following terms and establish the relationship of each in food web: Producer, Consumer, Herbivore, Carnivore, Decomposer, Food chain and Food web
*Describe the energy losses between trophic levels and infer the advantages of short food chains
*Describe and interpret pyramids of Number and Biomass

ECOLOGY is the branch of biology that studies relationships between living organisms and the non-living components of the environment in which they live.
Organism’s interactions may be competitive or beneficial. Organisms may interact with one another in several ways. Some of these relationships include producer/consumer, predator/prey, or parasite/host relationships.

Why do we study Ecology?

Curiosity – How does the world around us work? How are we shaped by our surroundings?
Responsibility – How do our actions change our environment? How do we minimize the detrimental effects of our actions? Overfishing, habitat destruction, loss of biodiversity, climate change.
Sustainability – a property of human society in which ecosystems (including humans) are managed such that the conditions supporting present day life on earth can continue.
Ecology helps us understand complex problems in the nature.

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DIGESTIVE SYSTEM

The digestive system also known as the alimentary canal or gut is a long tube running from the mouth to the anus, with associated organs together with a number of associated glands that help in digestion. The human digestive system is well adapted to all of these functions.
Explain why most food must be digested?
Most food substances are insoluble in water and are made up of large complex organic molecules. They cannot pass through the wall of the villi and the capillaries. So digestion helps to convert large complex insoluble molecules into simple soluble molecules so that they can pass through the wall of the capillaries. There are five processes in digestion.

1. Ingestion

2. Digestion Mechanical digestion Chemical digestion

3. Absorption

4. Assimilation

5. Egestion

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DIFFUSION

Diffusion is the movement of molecules from a region of high concentration to a region of low concentration down a concentration gradient until evenly distributed. Concentration gradient: the difference in concentration between two regions.

Why does diffusion occur?

1. There is a great deal of empty space between molecules of all substances. (The spaces are more in gases, less in liquids, and least in solids). 2. As all the molecules are always in a constant random motion they collide all the time.

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CELL DIVISION

All the multicellular organisms grow from an original single cell (zygote) formed by joining of two sex cells which divides repeatedly to form the cells of the adult organism. New cells come only from the pre-existing cells by cell division. Hence, cell division is very important for the continuity of life.
The process where new cells are derived from other cells is called cell divisions. Before the cell divides the nucleus of the cells divides first (nuclear division) and it is followed by the division of the cytoplasm (cytoplasm division). Chromosomes appear clear only at cell division and they become short and thick. Before that the chromosomes are very long and thin. Each chromosome has a specific shape and size so it is easy to identify different chromosomes. Each chromosome exist in pairs (homologous; exactly the same, pairs).
The nucleus and particularly the chromosomes within it play an important role in the continuity of one generation to another. In definition chromosomes are thread like structures found inside the nucleus which carries hereditary information from one generation to another. Chromosomes contain chemical DNA which makes exact copy of itself during nuclear divisions resulting in the doubling of the chromosomes.
Each species has a fixed number of chromosomes. Example human beings have 46 chromosomes, meaning 23 pairs of chromosomes. The number of chromosomes for one species is the same for all of its body (somatic) cells. The number of chromosomes in a sex cell would be half that of the number found in the body cell. Example the human egg or sperm cell will contain 23 chromosomes and in this case they are not in pairs. Diploid and Haploid cells

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CELLS

Cells are the basic structural and functional unit of life. Cells provide structure and stability to an organism. Cells provide energy and a means of reproduction for an organism. Organisms are made up of cells. Organisms containing only one cell in their body are called unicellular organism. Example Amoeba (animal), Chlorella (plant).

Organisms containing many cells in their body are called multi cellular organisms. Example: rabbit, mango tree. Scientists estimate that our bodies contain anywhere from 75 to 100 trillion cells. Cytology is the study of cells. Cells are very small in size. Cells range in size from 1 to 100 micrometers. Microscope is needed to study the cells. But an ordinary compound microscope is not enough to study the details of a cell. With the help of Scanning Electron Microscope and Transmission Electron Microscope, cell biologists are able to obtain detailed images of the smallest of cell structures.

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