B1 - Topic 1 - Classification, Variation and Inheritance

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Unit B1 – Influences on Life

 

Topic 1 – Classification, Variation and Inheritance

 

Kingdom

Phylum

Class

Order

Family

Genus

Species

 

Binomial Naming System

 

·         Easier to identify existing and new species

·         To see how closely organisms are related

·         To identify biodiversity in and area and protect biodiversity hotspots

·         Named using the genus and species

·         Species must be able to have fertile offspring

Fungi

-        Multi-cellular

-        Cell wall (cellulose)

-        Complex cell structure

-        Saprophytic feeders (no chlorophyll)

 

Protoctista

-        Mostly uni-cellular

-        Complex cell structure

 

Prokaryote

-        Uni- cellular

-        Simple cell structure (no nucleus)

 

Animalia

-        Multi-cellular

-        No cell wall

-        Complex cell structure

-        Heterotrophic feeders (no chlorophyll)

 

Plantae

-        Multi-cellular

-        Cell wall (cellulose)

-        Complex cell structure

-        Autotrophic feeders (chlorophyll)

 

 

Viruses do not count as living organisms as they do not show all 7 life processes:

-        Don’t respire

-        Don’t feed

-        Don’t use senses

-        Can’t reproduce without being in a living cell

-        Don’t excrete

-        Don’t grow or move

Phylum Chordata

 

Vertebrates have a back bone (supporting rod that runs the length of their body)

 

Vertebrates                                       Invertebrates

Mammals                                            Molluscs (snails)

Amphibians                                        Sponges

Birds                                                      Arthropods (insects)
Reptiles                                                                Coelenterates (Jelly fish)

Fish                                                        Worms

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Classifying Vertebrates

 

Oxygen Consumption - Organisms can be characterised by the way they absorb oxygen 

Fish: Have gills to gain oxygen from water

Amphibians: Have gills when young then have lungs but can absorb oxygen through moist skin too

Mammals, Reptiles and Birds: Have lungs

 

Thermoregulation - Organisms can be characterised by how their internal body temperature is controlled            

Homeotherms: Keep body temperature constant and often warmer than surroundings by reactions occurring all over the body

Poikilotherms: Body temperature varies based on the surroundings

 

Reproduction - Organisms can be characterised by how the reproduce

Mammals: Viviparous – fertilisation occurs internally and the mother gives birth to young which she feeds milk

Fish: Fertilisation occurs externally

Reptiles: Oviparous – lay eggs

 

Difficulty with Classification

 

·         Species: A group of organisms that can interbreed and produce fertile offspring

·         Some organisms do not breed by sexual reproductions, eg bacteria and fungi, so it is difficult to classify them as the same species

·         The definition of a species is not always clear because two closely related species can breed and produce hybrids

·         Hybrids are usually infertile but not always

·         A ring species is a group of related populations living in neighbouring areas that can interbreed – populations furthest apart cannot however

·         An example is the herring gull

 

Variation

 

·         Two causes of variation: genes and environment

·         The combining of genes from the…