Evolution slides (H1)

EVOLUTION

Learning outcomes: 4(a) Explain why variation (as a result of mutation, meiosis and sexual reproduction) is important in natural selection (b) Explain, with examples, how environmental factors act as forces of natural selection (c) Explain the role of natural selection in evolution. (d) Explain why the population is the smallest unit that can evolve. (e) Explain how genetic variation (including harmful recessive alleles) may be preserved in a natural population.

Concept of Species - Biological Species Concept - Ecological Species concept - Morphological Species concept - Genetic Species concept - Phylogenetic Species concept PG 1

Same species or Different species? Same species, different breeds

What defines a “species”? • There are different approaches to defining how species are identified; each approach is known as a species concept. • The concept of species may be defined in a variety of ways: (A) Biological species concept (B) Ecological species concept (C) Morphological species concept (D) Genetic species concept (E) Phylogenetic species concept 1. Definition 2. Advantages 3. Limitations PG 1

Species is the lowest taxa in the hierarchy of biological classification PG 1

• Definition: A species refers to a group of closely related organisms which are capable of interbreeding in nature to produce viable, fertile offspring and are reproductively isolated from other species. Biological species concept PG 2

Viable but sterile! Female Horse Male Donkey Horse & donkey are not the same species Mule PG 2

Tigress Male Lion Tiger and Lion are not the same species Liger Viable but sterile! PG 2

Miniature Poodle Schnauzer Schnoodle Poodle and Schnauzer: same species Viable & Fertile!