UNIT 1- Nature and Variety

 


What exactly makes something alive? Why are cells considered the building blocks of life? In this post, we'll uncover the key characteristics of living organisms and explore the differences between prokaryotic and eukaryotic cells.


CHARACTERISTICS OF LIVING ORGANISMS:

There are 8 characteristics of living organisms. For this specification, all you need to remember is MRS GRENC. This stands for:

Movement

Reproduction

Sensitivity

Growth

Respiration

Excretion

Nutrition

Control


Now, let's explain these key terms.

Movement= Every living organism moves their body parts as a part of their normal lives. We need                              movement for getting from and to places, even for the smallest of tasks like picking up                            and dropping a pencil.

Reproduction= Producing offspring is necessary and every living organism is capable of doing so.                                   Whether it is a human or an ant or a flower, we all produce offspring.

Sensitivity= This allows us to respond to the environment around us. Responding to touch, sound etc.                        will count as sensitivity

Growth= Every living thing grows is some sort of way or form. From a plant growing taller to organs                   growing inside a baby's body, growth varies in every living organism.

Respiration= A chemical process which takes part in the cells of a living organism. This process breaks                       down glucose to release energy. However, do not confuse this with breathing. Since every                         living organism needs energy, respiration is essential.

Excretion= The removal of waste products from our body is called excretion. 

Nutrition= Living organisms need nutrition to survive. This nutrition comes from the food we eat.                            plants, bacteria and us, we all eat food. Hereby, nutrition is gained and used in our bodies.

Control= This is also knows as homeostasis, and it includes things such as controlling temperature, PH                  levels, and blood sugar levels.


EUKARYOTIC CELLS:

These are cells with a true nucleus. Basically, cells that have a nucleus containing DNA and other membrane bound organelles. Examples of this is plant cells and animal cells.



 Functions:

Cell Membrane= controls what goes in an out of the cell.

Cytoplasm= site of all chemical reactions .

Mitochondria= releases energy.

Nucleus= controls the cell's activities and stores the DNA.

Chloroplast= contains chlorophyll to absorb sunlight for photosynthesis.

Cell wall= gives shape and structure to the cell.

Vacuole= stores cell sap.

Ribosomes= not shown in the diagram but they exist in both plant and animal cell. Their main function is protein synthesis.


PROKARYOTIC CELLS:

Prokaryotic cells are cells without a nucleus where DNA is free in the cytoplasm. These types of cells are mostly found in bacteria. 



Functions:

Chromosomal DNA= also known as the nucleoid, it controls activity and reproduction of the cell.

Flagellum= helps the cell move.

Plasmid DNA= smaller circular rings of DNA.

Capsule= protects the cell and is required for surviving in extreme conditions.


PATHOGENS:

  • A communicable disease is spread by a pathogen.
  • a microorganism that causes disease, e.g. bacteria and viruses.
  • Pathogens survive by doing the following. First, they will infect a host and reproduce or replicate if it's a virus. Then, they spread from their host and infect other organisms. They also have structural adaptations that enable them to cause further disease.


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