Unit 1 - Characteristics of Living Organisms 

Characteristics of Living Organisms

Biology is the study of living organisms, which are divided into 5 groups and the groups are

Kingdoms:

• Animal
• Plant
• Fungi
• Protoctists
• Prokaryotes

Characteristics of a living organism -

M - Movement: an action by an organism or part of an organism causing a change in position or place.

R - Respiration: Is the chemical reaction that breaks down nutrient molecules in living cells to release energy for metabolism.

S - Sensitivity: The ability to detect or sense stimuli in the external environment and to make appropriate responses.

G - Growth: A permeant increase in size and dry mass by an increase in cell number or cell size or both.

R - Reproduction: is the process that makes more of the same kind of organism.

E - Excretion: the removal of toxic material, waste products from metabolism (chemical reaction in cells, including respiration) and substances in excess of material.

N - Nutrition: The taking in of materials for energy, growth and development; plants require light, CO2 and water and ions; animals require organic compounds and ions.

Basic Classification

There are millions of species of organisms on earth. ==A species id defined as a group of organisms that can reproduce fertile offsprings.== These species can be classified into groups, by features that they share, eg - all mamals have bodies covered in hair, feed young from mammary glands and have external ears (pinnas).

The Binomial System

Organism were first classified by a Swedish naturalist called Linnaeus in a way that allows sud division of living organisms into smaller and more specialised groups.

The Species in these groups have more and more features in common the more subdivided they get.

He named organism in latin, using binomial system, where the scientific of a organism is made up of two parts, starting with %%Genus%% (always given a %%capital letter%%) and ==Species== (staring with a ==lowercase letter==)

So when typed binomial names are always in italics, Example Homo Sapiens which indicates they are latin.

The sequences of classification is:

1. Kingdom
2. Phylum
3. Class
4. Order
5. Family
6. Genus
7. Species

Originally, organisms were classified using morphology (the over all form and shape of the organism, example - whether it had wing or legs) and Anatomy (the detailed body structure as determined by dissection)

An example of Linnaeus’s System of Classification

Kingdom → Animalia

Phylum → Chardata

Class → Mammalia

Order → Primates

Family → Hominidae

Genus → Homo

Species → Homo Sapiens

As the technology advanced, microscopes, knowledge of biochemistry and eventually DNA sequences allowed us to classify organisms using a more scientifically way.

The study of DNA sequences of different species, show that the more similar the base sequence is in the DNA of two species, the more closely related those 2 species are.

This means that the base sequences in a mammal’s DNA are more closely related to all other mammals than to any other vertebrate groups.

The sequences above show the Brachinus armiger are more closely related to Brachinus hirsutus than to any other species in the list as their DNA sequences are identical expect for last but one base.

As the DNA sequences are used to code for, amino acid sequences in protein, as the similarities in the amino acid sequences can also be used to determined how closely related species are.

The common cell structures:

The cells of living organisms contain cytoplasm, cell membrane, DNA as genetic material (either found in the nucleus or free in the cytoplasm)

When cells are view under a electron microscope, all cells also contain: ribosome for protein synthesis, enzymes for respiration (in many but not all cells, found in mitochondria)

There are 5 kingdoms:

The first division of living things in the classification system is to put them into one of 5 kingdoms, they are :- animals, plants, fungi, protoctists and prokaryotes.

Main Feature in animals are :-

• Multicellular
• Cell contains a nucleus but no cell walls or chloroplast.
• They feed on organic substances made by other living things.

Main Features in Plants are :-

• Multicellular
• Cells contain a nucleus, chloroplast and cellulose cell walls.
• They all feed by photosynthesis.

Main Features in all Fungi :-

• Usually multicellular
• Cells have nuclei and cell walls (not made cellulose).
• Do not photosynthesis but feed by saprophytic (feed on dead or decaying material)
• The fungi reproduce by making spores that can be carried by the wind
• Most fungi are saprotrophs or parasitic (on alive material) nutrition.

Features of Protoctists :-

• Most are unicellular but some are multicellular
• All have nucleus, some may have cell walls and chloroplasts
• Some protoctists photosynthesis and some feed on organic substances
• Examples: Ameba, Plasmodium

Main Features of Prokaryotes :-

• Example Bacteria, Blue green algae
• They are often unicellular
• Cells have cell wall (not made of cellulose), and cytoplasm but no nucleus or mitochondria.

Features of Virus :-

• Virus are not cells
• They are made up of genetic material, rounded by a protein coat.
• Viruses are paracites which multiply when it enters another organism (host)
• Virus are not in any kingdom, they are classified on the basis of the type of genetic material and the protein coat they have.

Vertebrates

All animals that have vertebral column or backbone.

All vertebrates have internal skeleton made of bone and cartilage

Example: Fish, amphibians, reptiles, birds, and mammals.

Invertebrates

Invertebrates are animals that do not have vertebral column or backbones.

Arthropods species have segmented bodies, an exoskeleton and joint legs.

Hard exoskeleton allows arthropods to live on dry land.

As they grow they mold their exoskeleton, some mold once in their lives others mold only during early stages of life.

Ferns and flowering Plants

Ferns and flowering plants multicellular.

Some parts of any plants are green, cost by the presence of the pigment chlorophyll which absorbs energy for sunlight for the process of photosynthesis.

Both ferns and flowering plants have transport systems consists of small vessels ( xylem and phloem)

The plant kingdom includes organisms such as ferns and flowering plants.

Features of Ferns

• Ferns are a group of plants that have strong stems, roots and leaves.
• The leaves have waxy cuticle.
• Fern have leaves called fronds
• Don’t produce flowers but instead produce by spores produced on the underside of the fronds.

Features of flowering plants

• Flowering plants have true stems, roots and leaves
• Reproduce sexually by the means of flowers and seeds
• Seeds are produced inside the ovaries found at the base of the plant.
• Can be divided into 2 groups monocotyledons (Wheat plants) and dicotyledons (sunflowers)

Distinguishing between Monocotyledons and Dicotyledons -

• Flowers -
  • Flowers formed from monocotyledon contain petals in multiples of 3
  • Flowers from dicotyledons contain petals with the multiples of 4 or 5
• Leaves -
  • Leaves from monocotyledon have parallel leaf veins
  • Leaves from dicotyledon have reticulated (interconnected and form a web like network in the leaf) leaf veins.