classification and evolution

Classification

Name given to the process by which living organisms are organised into groups

Name of the hierarchy

Taxonomic hierarchy

Seven groups in taxonomic hierarchy

Kingdom

Phylum

Classification

Order

Family

Genus

Species

Broadest and biggest group is…

Kingdom

Smallest and most specific group is…

Species

Classification reasoning

To help identify organisms

To predict characteristics

To find evolutionary links

Explanation: to help identify

Classification provides clear and defined approach so organisms belonging to a species can be easily identified

Explanation: to predict characteristics

If several organisms have specific characteristics it is very likely other individuals in the same group to have that characteristic

Explanation: to help find evolutionary links

Species in the same group probably have the same characteristics because they have evolved from a common ancestor

How are organisms classified?

1. System begins with separating organisms into the three domain system: Archea, Bacteria, Eukaryota

2. These are the broadest levels

3. As you move down the hierarchy there are more groups on each level however fewer organisms in each group

4. Organisms in each group become more similar and share of the same characteristics

5. The system ends with individual species

6. These are the smallest units

Species

The name given to organisms which are able to reproduce to produce fertile offspring

Viable offspring vs fertile offspring

Viable - the offspring produced survives but can't necessarily reproduce

Fertile - they are able to reproduce

System of naming organisms is called…

Binomial nomenclature

• Naming organisms is useful because…

It helps to identify the relationships between species

• Before organisms were named according to physical characteristics, behaviour or habitat

• Problem because some organisms can have more than one common name.

• May have different names in different languages

• Naming consists of two parts…

• First name - Genus ‘generic name’

• Second name - Species

• Should be written in italics, underlined and lowercase with the exception of the capital letter at the beginning of the Genus name e.g lion - Panthera leo

the five kingdoms - why?

• more species were discovered

• more was being discovered about organisms

• it became increasingly difficult to divide living organisms into just two kingdoms

• development of microscopes meant better observation of cellular structures, identifying the significant cellular differences in bacteria from other organisms

What are the 5 kingdoms?

• Prokaryotae

• Protoctista

• Fungi

• Plantae

• Animalia

Prokaryotae - features

1. unicellular

2. no nucleus

3. no membrane bound organelles

4. small ribosomes

5. ring of naked dna

6. no visible feeding mechanisms - nutrients are absorbed through the cell wall or produced internally by photosynthesis

e.g E.coli

protoctista - features

1. mainly unicellular

2. nucleus and other membrane bound organelles

3. some have chloroplasts

4. some are sessile or move using cilia, flagella or amoebic mechanisms

5. nutrients are acquired through photosynthesis ( autotrophic feeders ) or ingest other organisms (heterotrophic feeders) - some are parasitic

e.g amoeba

fungi - features

1. unicellular or multicellular

2. nucleus, other membrane-bound organelles, and a cell wall mainly composed of chitin

3. no chloroplasts

4. no mechanisms for locomotion

5. most have a body or mycellium made of threads or hyphae

6. nutrients are acquired through absorption - mainly decaying material (saphotrophic feeders) - some are parasitic

7. most store their food as glycogen

plantae - general features

1. multicellular

2. other membrane-bound organelles, including chloroplasts, and a cell wall mainly composed of cellulose

3. all contain chlorophyll

4. most are immobile but some gametes travel using cilia or flagella

5. nutrients are acquired by photosynthesis - autotrophic

6. store food as starch

animalia - features

1. multicellular

2. no chloroplasts

3. nucleus and other membrane-bound organelles

4. move with aid of cilia, flagella, and contractile proteins, sometimes in the form of muscular organs

5. nutrients are acquired by ingestion - heterotrophic

6. food stored as glycogen

Scientists are now able to study the evolutionary links between organisms due to…

• study of genetics and biological molecules

• also comparing the similarities in DNA and proteins of different species so that they can discover evolutionary relationships between them

Woese’s system groups organisms using…

differences in the sequence of nucleotides in the cells’ ribosomal RNA (rRNA) as well as the cells’ membrane lipid structure and their sensitivity to antibiotics

Eukarya - ribosomes and form of rRNA

• 80s ribosomes

• RNA polymerase

• contains 12 proteins

Archaea - ribosomes and form of rRNA

• 70s ribosomes

• RNA polymerase of different organisms contain 8 - 10 proteins

• very similar to eukaryotic ribosomes

Bacteria - ribosomes and form of rRNA

• 70s ribosomes

• RNA polymerase contains five proteins

Archaebacteria

can live in extreme temperatures

• hot thermal vents

• anaerobic conditions

• highly acidic conditions

e.g methanogens live in anaerobic sewage treatment plants and make methane

Eubacteria

found in all environments - most bacteria in the eubacteria kingdom

Eubacteria and Archaebacteria are classified as their own kingdoms because…

they have different chemical makeup for e.g peptydoglycan is in the cell wall of eaubacteria whereas in archaebacteria it is not

Woese’s six kingdom system

1. Eubacteria

2. Archaebacteria

3. Protoctista

4. Fungi

5. Plantae

6. Animalia

phylogeny

evolutionary relationships between organisms

Advantages of phylogeny

• Shows evolutionary relationships

• Shows evolutionary timeline

• Is continuous whereas classification requires discrete taxonomical groups so it doesn’t force any organisms into specific unfit groups

• Hierachal nature of linnaean classification implies that different groups within the same ranks are equivalent e.g orchids and cats are in the same family but orchids have existed over 100 million years whereas cats are 30 million which implies that they are the same

• certain groups could have longer histories or different levels of diversity

explain phylogeny tree