Biology AQA new AS level unit 2, classification.

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Classification - organisation of living organisms into groups based on number of accepted principles.

Species - basic unit of classification. a group of organisms that share certain observable characteristics, are able to breed together to produce fertile offspring and occupy same ecological niche. Concept of a species:

  • Members have certain things in common:
  • 1. Similar to 1 another but different from other species - similar genes so resemble each other, similar development patterns, immunological features and eco niche.
  • 2.Capable of breeding to produce living, fertile offspring - belong to same gene pool.

Binomial system - universal. 1st name (genus) is generic. 2nd name (species) is specific. Italics or underlined if handwritten. "Sp" written if species unknown.

Taxonomy - theory and practice of biological classification.

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Classification Continued.

2 forms of classification:

  • 1. Artificial - divides organisms according to differences useful at time. These are analogous characteristics as have same functions but diff evolutionary origins.
  • 2. Natural - based on evolutionary relationships. Classifies using shared features from ancestors, arranges groups into hierarchy, relationships based on homo characters that have similar evolutionary origins regardless of function.

Taxonomy- studies their positions in hierarchical order = taxonomic ranks. Based on evolutionary line of descent. Kingdom, phylum (different body plans to other phylum), classes, order (additional common features), family (subtle differences), genera and species.

Phylogeny - evolutionary relationship between organisms shown in phylogenetic tree.

Species change and evolve, variation due to artificial selection. Many are extinct with no fossil record. Some don't reproduce sexually and some are isolated so no interbreeding. Sterile due to odd number of chromosomes.

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i thought it was v. useful. thanksx

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