GCSE Biology B2

Classification

Natural Classification: based on evolutionary relationships & genetic similarities

Artificial Classification: based on appearance

Groups: phylum, class, order, family, genus, species

A genus is a group of closely related species.

A species is a group of organisms that can interbreed to produce fertile offspring.

Classification systems change over time as new species are discovered that may not fit in current categories and due to advances in ICT.

Evolutionary trees can show evolutionary relationships.

Species

A species is a group of organisms that can interbreed to produce fertile offspring.

Asexual Reproduction: Make a copy of itself. No interbreeding. Doesn't fit definition of species.

Hybrids: Two organisms from different species interbreed to create infertile offspring. Difficult to classify as they aren't new species.

Evolution is a continuous process as environments and conditions change, causing organisms to change too over time.

The Binomial System: Each species is given a two-part Latin name.

The first part is the genus, the second part is the species.

The Binomial System is a universal language, it is the same in each language - no confusion.

Closely related species have recent common ancestors. They tend to look alike and live in similar habitats (not always). You have to consider how they are related in evolutionary terms and their type of environment.

Pyramids of Biomass and Numbers

Each bar on a pyramid of biomass shows the dry weight of living material at that stage of the food chain.

They are always pyramid shaped - each bar is shorter than the previous one.

Unfortunately, you have to kill the organism to weigh it's dry mass. It's…