MICROORGANISMS AND THEIR EFFECTS ON LIVING

THINGS

CHAPTER 1 (FORM 5)

WHAT IS MICROORGANISMS?

Microorganisms / microbes:- Living things which are so small- Cannot be seen with naked eye- Only visible under the microscope

MICROORGANISMS CLASSIFICATION

FungiBacteria

Protozoa

Viruses

Algae

BACTERIA

GENERAL STRUCTURE OF A BACTERIUM

CHARACTERISTICS OF BACTERIA

• Unicellular – made up of one cell• Length – few micrometres• Cell wall – peptidoglycan [complex

polysaccharide combined with amino acids]• Slimmy capsule outside cell wall – protection• Plasma membrane• Doesn’t have a nuclear membrane to enclose its

DNA

• Stores food in the form of glycogen granules in its cytoplasm.

• Flagella – used for swimming

• Exist in different shapes. [spherical, rod-shaped, comma shaped, spiral / spring shaped]

VARIOUS SHAPES OF BACTERIA

REPRODUCTION OF BACTERIA

ASEXUALLY

• Binary fission• Each binary fission takes 20 - 30 minutes

SEXUALLY

• Conjugation process

Notes:

Favourable condition for reproduction of bacteria are dark, moist, and moderately warm conditions, and with the presence of nutrients.

BINARY FISSION OF BACTERIA

CONJUGATION

SPORE FORMATION IN BACTERIA

If conditions are unfavourable for reproduction:

1. Bacteria will form spores.

2. Spores have thick walls to protect themselves against dryness, strong light or extreme temperatures.

3. Wall of the spores breaks open and become active when favourable conditions return.

MODES OF NUTRITION AMONG BACTERIA

1. Photosynthesis – some bacteria have chlorophyll & able to make their own food by using light energy.

2. Chemosynthesis – some bacteria make their own food by using chemical energy obtained from oxidising chemicals such as ammonia & nitrite.

3. Saprophytic nutrition – a group of bacteria known as putrefying bacteria obtain food from dead and decaying organisms / matter.

4. Parasitic nutrition – some bacteria are parasites. They obtain food from other living organisms & cause diseases.

FUNGI

CHARACTERISTICS OF FUNGI

• Do not have chlorophyll• Colourless• Hypae – each hypa contains cytoplasm & multinucleated• Cell wall – made of chitin• Unicellular – some fungi such as yeast

REPRODUCTION OF FUNGUS

ASEXUALLY

• Spores• Budding

SEXUALLY

• Conjugation

BUDDING IN YEAST

MODES OF NUTRITION AMONG FUNGI:

1. Saprophytic nutrition – Obtain food from dead & decaying matter. Secrete enzymes onto food to digest it & absorb the products of digestion. Eg:bread moulds & yeast.

2. Parasitic nutrition – Eg: fungus which causes potato blight (phytophthora infestants) & fungus which causes athlete’s foot (Tinea)

PROTOZOA

CHARACTERISTICS OF PROTOZOA

• Unicellular animals – have structure of general animal cells.

• Found in aquatic habitats or semi-aquatic habitats.

• Examples: Amoeba, Paramecium and Trypanosome.

MODES OF NUTRITION AMONG FUNGI:

• Saprophytic nutrition :

Example: Amoeba and Paramecium – feed on decaying matter at the bottom of ponds and drains.

• Parasitic nutrition:

Plasmodium and Trypanosome – parasites of human beings, feed on cells in the human body and cause diseases

VIRUSES

CHARACTERISTICS OF VIRUSES

• Smallest microorganisms (20 – 400 nm)• Various shapes (spherical, rod-shaped or rocket-

shaped)• Simple structure • Doesn’t have a plasma membrane, cytoplasm or

nucleus.• Made up of two components:

a. nucleic acids – DNA or RNA (contains information)

b. protective protein coat

• Characteristics of living things:

a. They have nucleic acids

b. They can reproduce

• Characteristics of non-living things:

a. They do not respire, feed or excrete

b. They can be crystallised

• Can reproduce in a living host cell by using materials from the host to make new viruses.

REPRODUCTION OF A BACTERIOPHAGE

ALGAE

CHARACTERISTICS OF ALGAE

• Green plants• Unicellular and multicellular• Spherical, oval-shaped or filamentous• Sea algae – can be a few metres tall (not

microorganism)• Contain chloroplast – make own food by photosynthesis• Reproduce sexually: conjugation• Reproduce asexually: binary fission and fragmentation• Live either aquatic or semi aquatic habitats