WJEC AS Biology Unit 2.1 - Classification and Biodiversity

Classification

• Putting/placing organisms into groups based on their evolutionary relationships

• Places organisms into discrete and hierarchical groups with other closely related species

Taxonomic levels

• Domain

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

• More closely related down the levels

Binomial system of naming organisms

• Genus + species used to generate unique binomial name

• Avoids confusion between organisms in scientific communications

• Universal - same in all languages

Taxa

• Groups within a system of classification

• Taxa are discrete

  • At any level of classification, an organism belongs in one taxon and in no othe

The need for classification

• A phylogenetic classification system allows us to infer evolutionary relationships

• Can predict other characteristics of a new or organism based on knowledge of its species

• Ease of communication

• More useful to count families when describing health of an ecosystem or rate of extinction

Tentative nature of classification

• Classification may change as additional information becomes available

• system for classification depends on our current knowledge

• Systems may be altered as knowledge advances

• Classification can change to incorporate new nucleotide base sequencing

The 3 domain system

• biochemical evidence shows the kingdom prokaryotes can be split into 2 separate groups based on fundamental biochemical differences. All other organisms have eukaryotic cells

• Eubacteria

• Archaea

• Eukaryota

• The organisms of each domain share a distinctive, unique pattern of rRNA, which established their close evolutionary relationship

Eubacteria

• the true bacteria

• Prokaryotic cells structure

Archaea

• Bacteria

• Prokaryotic cell structure

• Includes the extremophile prokaryotes

Extremophiles

Organisms able to exist, survive and grow in extreme environmental conditions, e.g. extremes of temperature, pH, salinity and pressure

Eukaryota

• Includes all eukaryotic organisms

  • Plantae

  • Animalia

  • Fungi

  • Protoctista

The 5 Kingdom system

• Prokaryotae

• Protoctista

• Fungi

• Plantae

• Animalia

• Prokaryota = eubacteria and archaea

• Protoctista, Fungi, Plantae and Animalia = Eukaryota

Prokaryota

• composed of prokaryotic cells, which lack a nuclear envelope and membrane-bound organelles (the cell wall does not contain cellulose or chitin)

• Microscopic

• Includes all bacteria, Archaea and Cyanobacteria

Protoctista

• mainly single cell eukaryotes

• No tissue differentiation

• Some have only one cell, some have many similar cells

Fungi

• Heterotrophic eukaryotes

• Cell walls of chitin

• Most have filaments called hyphae

• Reproduce by spores

Plantae

• multicellular eukaryotes

• Photosynthetic

• Cellulose cell walls

• Some reproduce with spores, others with seeds

Animalia

• Nervous coordination

• Multicellular eukaryotes

• No cell wall

• Heterotrophic

• Great range of body plans, most are motile at some stage in their life cycle

Summary of 5 kingdoms

The use of physical features to assess relatedness

• look for type of features → discover the type of evolution which has taken place

Divergent evolution

• The development of difference structures over long periods of time, from the equivalent structures is related organisms

• Similar development/evolutionary origin

• Share a recent common ancestor

• Gives rise of homologous structures

Adaptive radiation

Divergent evolution

Homologous structures

Structures in different species with a similar anatomical positions and developmental origin but different functions, derived from a recent common ancestor. Have evolved from the same original structure for different functions

Convergent evolution

• The development of similar features in unrelated organisms over long periods of time, related to natural selection of similar features in a common environment

• Difference developmental/evolutionary origin

• Do not share a recent common ancestor

Analogous structures

Using structures to assess relatedness

Assessing relatedness with genetic evidence via biochemical methods

Genetic profiling

DNA hybridisation

DNA base sequences

Amino acid sequences

Species

Biodiversity

Differences in biodiversity

Importance of biodiversity

Assessment of biodiversity in a habitat

Assessment of biodiversity within a species at a genetic level

Genetic polymorphism

How generic biodiversity can be assessed

Abundance

Richness

Assessment of biodiversity at a molecular level

Generation of biodiversity

Natural selection

Types of adaptations

Anatomical adaptations

Physiological adaptations

Behavioural adaptations