We classify groups according to their characteristics.
Animals with backbones are called vertebrates. The 5 vertebrate groups are:
They exchange oxygen and carbon dioxide across gills, lay eggs (oviparous) and fertilise externally.
Exchange gases through moist, permeable skin and lay externally fertilized eggs.
-Reptiles and Birds
Exchange gases via their lungs and lay internally fertilised eggs.
Give birth to live young, which grow inside the body of the mother. Eggs are fertilised internally.
Multicellular. Cells lack a cell wall and chlorophyll, feed heterotrophically (food from environment)
Multicellular. Cells have chlorophyll and a cellulose cell wall. Obtain food autotrophically (food from photosynthesis)
Multicellular. Cells lack chlorophyll. Have a cell wall with no cellulose. Feed saprophytically (dead organic matter)
Unicellular, exception of seaweed. Have a distinct nucleus.
Unicellular. Without a distinct nucleus.
All organisms have a 2 part name, or binomial name.This system prevents confusion over having many different names for the same species.
For examples, humans are homo sapiens.
Homo is the genus name.
Sapiens is the species name.
Bionmial classification allows scientists to:
- Communicate information about the all the different species.
- Recognise areas of great biodiversity that should be targets for conservation efforts.
What is a species?
A common definition for species is 'organisms that are capable of breeding together to produce fertile offspring.' (Fertile means it can reporduce)
The offspring of 2 different species are known as hybrids. They are usually infertile.
There are some complications with the definition of species because...
- Not all hybrids are sterile. For example many plant hyrbrids are fertile.
- Not all organisms reproduce sexually. Instead they produce asexually.