1.3Chapter 1: Classification and Life

Classification and species — Alhussan Biology - Stage 7 Revision Notes & Topical Questions

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Biology 1.3 Classification and species — Alhussan International Academy — Biology (Stages 7–9) notes: Explain why organisms are classified, define a species, and use two-part scientific names.Classification = sorting organisms into groups using their similarities and differences.…

Importance
Big groups first
Smaller groups
Living organisms
Different species
Identified species

Part 1 of 5Why classify

1Classification

Classification sorting organisms into groups using their similarities and differences.

Features can be easy to see, such as the number of legs or type of flower, or harder to see, such as root length or whether an animal has a backbone.

2Importance

Importance it shows how many different types of living organisms there are, makes them easy to identify and compare,
- and helps scientists worldwide know which organisms are discussed.

3History

Carl Linnaeus sorted organisms by physical features in the 1700s, and modern scientists also compare DNA.

Part 2 of 5Classifying organisms into groups

Big groups first

Big groups first is it a plant or an animal?
Plants make their own food, but animals eat other living things.

Smaller groups

Smaller groups this level is helpful but does not identify particular organisms,
- since birds all have feathers but include an ostrich and a hummingbird.

Living organisms

Living organisms a basic classification covers animals, plants, fungi and other groups, and asks about viruses.

Levels

Levels kingdom, phylum, class, order, family, genus and species, from largest to smallest.
Organisms in each smaller group have more features in common, and members of one species are the most closely related.

Part 3 of 5What is a species

Species

Species a group of organisms that can reproduce to produce fertile offspring (offspring that can themselves reproduce).

Different species

Different species they cannot usually breed with each other.

Hybrids

Hybrids when different species do breed, the offspring are hybrids, which are usually infertile.
A mule, the strong, intelligent offspring of a female horse and male donkey, cannot breed,
- so horses and donkeys are separate species and mules are not a species.

Limits

Limits asexual organisms and fossils cannot be tested by breeding,
- and some species form fertile hybrids,
- so structure, behaviour and DNA are also used.

Part 4 of 5Number of species

Number of species

Identified species

Identified species about 2 million species have been identified.

Estimates

Estimates biologists think there may be as many as 5 million species on Earth.

Why new species are hard to find

Why new species are hard to find they may be very small or rare, live in unexplored places such as the deep ocean,
- or live in areas with many species such as rainforests.

Part 5 of 5Naming species

Local names

Local names they vary and cause confusion, such as the clouded leopard, called the tree tiger in Borneo and the mint leopard in southern China.

Scientific name

Scientific name each species has a two-part name, and similar species share the first part.
Lions are Panthera leo, tigers Panthera tigris, horses Equus caballus and donkeys Equus asinus.
Humans are Homo sapiens.

Rules

Rules the first part is the genus, with a capital letter, and the second is the species, in lower case, both in italics or underlined.

Importance

Importance it tells scientists around the world exactly which organism is meant.

Key terms

Term	Meaning
Classification	Sorting organisms into groups by shared features.
Species	A group of organisms that can breed to produce fertile offspring.
Genus	A group of closely related species.
Kingdom	The largest group in classification.
Scientific name	A two-part Latin name made of genus and species.
Hybrid	The offspring of two different species, usually infertile.