Diversity of organisms

Learning Objectives List the five kingdoms used to classify plant and animals Discuss the plant kingdom with the flowering plant as an example Discuss the animal kingdom with the human as an example

Classification In order to organise information about the wide variety of life on earth a system of classification is required. Taxonomy is the study of classification.

Classification Old systems of classification were based on separating life into two categories: Animals and Plants. With developments in science came the discovery of new forms of life A more updated five kingdom system was proposed. It has since gained widespread acceptance by the scientific community.

Five kingdom system of classification Life on earth can be divided up into 5 Kingdoms Monera Protista Fungi Plantae Animalia

Five kingdom system of classification Each of the five kingdoms can be further subdivided into smaller categories. Each successive category contains organisms that are more and more similar. The final category into which organisms can be placed is the species. Members of the same species are capable of interbreeding to produce fertile offspring.

Monera (Prokaryotae) This kingdom contains about 10,000 identified species of bacteria. It is estimated that there are many more. Bacteria were the first organisms on earth. They are by far the most numerous organism on the planet.

Monera – main features They are mainly microscopic and single celled organisms. They do not have a membrane enclosed nucleus. They do have membrane enclosed organelles such as mitochondria and chloroplasts. They normally reproduce asexually.

Monera

Protista (Protoctista) Contains a wide variety of organisms from large plant-like algae seaweeds to single-celled organisms such as Amoeba. Protists are found almost anywhere water is present.

Protista – main features Contains single celled (Amoeba) and simple multicellular organisms (Algae) They have a membrane-enclosed nucleus Some feed by taking in organic substances (they absorb nutrients through the cell wall) Others can produce their own food by photosynthesis

Protista

Fungi Examples of fungi include mushrooms, mildews, moulds and yeasts. Fungi play a vital role in that they break down dead organisms and allow minerals to be recycled.

Fungi - main features They are mainly multicellular. They are composed of threads called hyphae. A Hypha consists of one or more cells surrounded by a tubular cell wall. Cell walls are made of a carbohydrate called chitin. They are unable to make their own food. Their method of reproduction involves spores.

Fungi

Learning Check Why do we have a system of classification? What is the study of classification called? What are the main differences between members of the first two kingdoms mentioned? What are the 5 kingdoms called?

Plants This kingdom includes the mosses, ferns and seed-producing plants. Seed producing plants can be further sub-divided into flowering and non-flowering.

Plants – main features All plants are multicellular Their cells have cell walls made of the carbohydrate cellulose Their cells often have large vacuoles They are eukaryotic – the have a true nucleus and membrane enclosed organelles). Chloroplasts containing the pigment chlorophyll which enables photosynthesis. All plants are autotrophs. They reproduce asexually and sexually.

Plants

Animals This kingdom includes jellyfish, flatworms, snails, roundworms, segmented worms, frogs, lizards, birds and humans. The first animals evolved in the sea about 700 million years ago.

Animals – main features All organisms in this Kingdom are multicellular They are eukaryotic - have a nucleus and membrane enclosed organelles Animal cells have no cell walls All animals are heterotrophic – they cannot produce their own food They normally reproduce sexually.

Animals

Learning Check What are the main differences between plants and animals with regard to cells? What other features distinguish plants from animals?