Variety of living organism

Kingdoms

Animal kingdom and plant kingdom

Animal kingdom divides to invertebrates and vertebrates, the vertebrates include; fish, amphibians, reptiles, birds, and mammals.

Vertebrates

Vertebrates are animals which have a backbone (vertebral column). The backbone consists of a chain of cylindrical bones joined end to end.

Backbone protects the spinal cord.

The front end of the spinal cord expands to form a brain which is enclosed and protected by a skull.

There are 5 groups of vertebrates (mentioned above)

Body temperature

Fish, amphibians and reptiles are referred to as cold blooded (poikilothermic). Their body temperature depends on the surrounding temperature.

Warm blooded animals (homeothermic) keep their body temperature more or less constant, despite the variations in the external temperatures.

Warm blooded animals have a thermoregulatory mechanism to keep their body temperature constant.

Mammals

·       Mammals are homeothermic vertebrates with 4 limbs.

·       They have hair or fur

·       They have 2 types of glands in the skin; sweat glands and sebaceous glands(oil)

·       They have mammary glands to produce breastmilk.

·       Mammals give birth to their young.

·       They look after their young ones until they can look after themselves.

·       Presence of ear pinna.

Plants

Dicot leaf                                                         Monocot leaf

The plants (with well-developed xylem and phloem) are divided into non-flowering and flowering plants.

Flowering plants are divided into dicotyledons and monocotyledons.

Comparison between dicotyledons and monocotyledons

Fungi

Fungi includes; toadstools, puffballs, mushrooms and bracket fungi that grow on tree trunks. There is also mold fungi which grows on stale bread, cheese, fruit and other food.

Many of the mold fungi live in soil or dead wood.

Yeasts

Oil droplets and glycogen granules are also present in the cytoplasm of a yeast cell along with other food reserves.

Yeast cells are spherical shape cells. They live in situations where sugar is likely to be available; for example, in the nectar of flowers or the surface of fruits.

The thin cell wall is made out of chitin.

Reproduction of yeast

Yeast cells produce by budding. An outgrowth from the cell appears, enlarges and is finally cut off as an independent cell.

When budding occurs rapidly, the individual does not separate at once and as a result, small groups of attached cells may sometimes be seen.

Fermentation

Yeast is of economic importance in promoting alcoholic fermentation

Yeast cells contain many enzymes, some of which can break down sugar into carbon dioxide.

Glucose                              ethanol (alcohol) + Carbon dioxide + energy (118KJ)

Alcoholic fermentation is a form of anerobic respiration.

Yeast cells are used in breadmaking process, beer and wine production, etc.…

Structure of fungi

Mycelium of Mucor

Many fungi are made up of cells but of microscopic threads called hyphae. The branching hyphae spread through the material on which the fungus is growing and absorbs food from it.

The network of hyphae that grow over or through the material is called mycelium.

Mushrooms and toadstools are the reproductive structures (fruiting bodies) of an extensive mycelium that spreads through the soil or the dead wood on which the fungus is growing.

Fruiting body of mold fungi is called sporangia (sporangium – singular)

The mycelium grows in or on the food as it digests and absorbs the nutrients.

Vertical hyphae grow from the mycelium and hold the fruiting bodies containing spores. Example; Mucor.

Some fungi produce chains of spores at their tips. Example; penicillium.

Structure of fungal hyphae

The hyphae are like microscopic tubes lined with cytoplasm.

In the center of the older hyphae there is a vacuole and the cytoplasm contains many nuclei, glycogen granules and oil droplets. There are no starch granules or chloroplasts.

The hyphae wall is made out of chitin, it is similar to cellulose but the chitin molecule contains nitrogen atoms.

In some species of fungi, there are incomplete cross walls dividing the hyphae into cell-like regions.

Nutrition of fungi

Most fungi are saprotrophs living on dead organic matter.

The hyphae secrete enzymes into the organic material and digest it to liquid products which then are absorbed back in to the hyphae and used for energy or for the production of new cytoplasm or hyphal wall.

Some fungi species produce cellulase enzyme which digest cellulose.

Saprotrophic fungi are the decomposes in most food webs and are largely responsible for the recycling of essential nutrients in the environment.

Reproduction of fungi

Fungi reproduce by releasing microscopic single cell spores.

Different types of fungi have different methods for reproduction;

1.  The spores are budded of from the tips of special hyphae. Each spore contains a little cytoplasm, one or more nuclei depending on the species.

2.  Some fungi species produce vertical hyphae. Each producing fruiting bodies called sporangium containing spores. Example; mucor.

3.  Penicillium fungus produce vertical hyphae form the mycelium and at their tips, produce chains of spores. These give the colony a blue green color and a powdery appearance

The type of reproduction in fungi is an example of asexual reproduction

When the spores are dispersed in air currents or by other methods and land on a suitable organic matter, they germinate to produce a new mycelium.

Bacteria

Bacteria can only be seen by higher powers of microscopes, because they are very small organisms consisting of single cells.

Their cell walls are made up of a complex mixture of protein, sugars and lipids. Some bacteria have slime capsule outside the cell wall. Inside the cell wall, there is a cell membrane and a cytoplasm which may contain granules of glycogen, lipids and other food reserves.

Each bacterial cell contains genetic material in a form of a single chromosome, forming a loop called as a nucleoid. It is not enclosed in a nuclear membrane. Some bacteria have circular rings of DNA (plasmids) carrying some of the bacterium’s genes.

Some bacteria have filaments called as flagella for locomotion

Nutrition of bacteria

Few species of bacteria contain a type of chlorophyll and can carry out photosynthesis process to produce their own food. This group of bacteria are called as cyanobacteria.

Most bacteria live in or on their food. They produce and release enzymes which digest the food outside the cell. The liquified products of digestion are then absorbed back into the bacterial cell. 

Respiration of bacteria

Aerobic bacteria are bacteria needs oxygen for their respiration. Anerobic bacteria are bacteria which does not need oxygen for respiration.

The bacteria used in filter beds of sewage plants are aerobic. The bacteria used to digest sewage sludge are anerobic (bacteria which produce methane gas).

Reproduction of bacteria

Bacteria reproduce by binary fission and cell division. Any bacterial cell can divide into two and the daughter cell becomes an independent cell.

In some occasions, cell division occurs every twenty minutes, resulting in a large colony of bacteria, in a very short time. This is one reason for why a small number of bacteria can seriously contaminate our food. This kind of reproduction is known as asexual reproduction.

classification of bacteria based on the shape

1.  Spherical bacteria (cocci)

Staphylococcus                 streptococcus         pneumococcus

(boils)                              (sore throat)              (pneumonia)

2.  Rod shaped bacteria (bacilli) 

Bacillus anthracis                                                 Salmonella Typhi

(anthrax)                                                    (typhoid fever)                                                                       

3.  Spiral bacterium (spirillum) 

Treponema                                                            Vibrio Cholera

(syphilis)                                                              (cholera)

Useful bacteria

Most bacteria are harmless or extremely useful.

Bacteria which feed saprotrophically bring about decay. Bacteria decompose dead matter consisting of excretory products and dead bodies of organisms. Accumulation of dead vegetation and animal bodies will occur in the environment producing bad odor and pollution if they are not decomposed.

Decay bacteria also release essential elements from the dead remains. Example; proteins are broken down to ammonia and ammonia is turned into nitrate.

Protein                              Ammonia     ^{nitrifying bacteria}               Nitrates

The nitrates are taken up from the soil by the plants, which then used them to build up their proteins.

The elements essential for living organisms including, Sulfur, Phosphorous, Iron, Magnesium, are recycled in the course of bacterial decomposition, in a similar way.

Bacteria can be used in the process of genetic modification (genetic engineering)

Harmful bacteria

Disease causing bacteria are called as pathogens. The organism in which they live and reproduce, is called as the host.

Pathogenic bacteria cause diseases because of the damage they do to the host’s cell. But most bacteria also produce poisonous waste products called as toxins.

The toxin produced by the clostridium bacteria (bacteria causing tetanus) is so poisonous that as a little amount can be fatal.  

Viruses

Virus structure

Virus structure

All viruses have a central core of RNA or DNA, surrounded by a protein coat. They have no nucleus, cytoplasm, cell organelles or cell membranes, though some forms have a membrane outside their protein coat called as an envelope.

Viruses are not complete cells and they are particles. They do not feed, respire, excrete or grow.

Virus reproduces only inside the cells of living organisms, using materials provided by the host cell.

The protein coat (capsid) is made up of regularly packed protein units called capsomeres each containing many protein molecules.

Virus reproduction

In the process of virus replication,

·       The virus sticks to the membrane of a suitable host cell.

·       The virus enters the cell, the protein coat breaks down releasing the DNA or RNA.

·       The viral DNA or RNA replicates and directs the host cell to make new protein molecules.

·       The new viruses escape from the host cell

Viruses are able to survive outside of a host cell, but to reproduce they must penetrate into a living cell. Mostly the virus particle sticks to the cell membrane of the host cell and then inject its DNA or RNA into to the cell’s cytoplasm, or the whole virus particle maybe taken in by a process called endocytosis.

The host cell maybe destroyed in the process of reproduction or the virus may escape wrapping themselves in pieces of the host’s cell membrane as they do so. These activities give rise to the signs and symptoms of diseases.

Viral diseases

In humans – common cold, Measles, Poliomyelitis, Mumps, Chickenpox, Herpes, Rubella, Influenza and AIDS. 

In plants – Chlorosis caused by Tobacco mosaic virus

 Protoctista

It is also known as the dustbin kingdom because they are a mixed group of organisms.

Most Protoctista are unicellular organisms which have their chromosomes enclosed in a nuclear membrane to form a nucleus.

Protoctista which looks like animal cells are known as protozoa.

Protoctista which look like plant cells are known as Protophyta

Protozoa

These are unicellular animals; they resemble animals in their feeding because they take in and digest solid food.

Amoeba is a protozoan which moves by a flowing movement of its cytoplasm; it feeds by picking up other microorganisms and bacteria.

Many protozoans propel themselves by structures called as cilia or flagella. Cilia are fine cytoplasmic hairs which cover the surface membranes of some protozoans, and flagella are longer than cilia and occur singly or in pairs. 

Protophyta

Organisms such as Chlamydomonas and euglena possess chloroplasts to make their own food by the process of photosynthesis.

Diseases caused by Protoctista

·       Malaria – Plasmodium Virax

·       Amoebic dysentery – Entamoeba Histolytica 

Prokaryotes and eukaryotes

All the organisms having a nucleus are considered as eukaryotic cell and all organisms with no nucleus, no mitochondria and no chloroplasts are known as prokaryotic organisms.  

Eukaryotic organisms include plants, animals, fungi and Protoctista. And prokaryotic include bacteria.