Lesson 2 — Species Concepts and Speciation

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What is a Species?

What is a Species?

During Linnaeus' time, species were groups of organisms that could be distinguished from each other.

This idea is not widely accepted today because members of the same species can look very different.

Example: sexual dimorphism - males and females of the same species have different physical features.

Because of this, scientists developed different species concepts to define what a species is from different perspectives.

Species Concepts

Species Concepts

One. Typological Species Concept

Species equals a group of organisms that share a common, idealized physical form. Also called the Morphological Species Concept.

Species are identified mainly through their morphological features (physical characteristics).

Four Postulates:

Two. Nominalistic Species Concept

Three. Biological Species Concept

History

Four. Evolutionary Species Concept

Five. Ecological Species Concept

Six. Phylogenetic Species Concept

How Many Species Currently Exist? Estimated total: about eight point seven million species.

Types of Species Some examples include: Chronospecies Subspecies.

Infraspecific Ranks

Mechanisms of Speciation

Genetic Models Natural selection Genetic drift Mutation.

One. Allopatric Speciation

Two. Peripatric Speciation

Three. Sympatric Speciation

Sympatric via Behavioral Isolation

Four. Parapatric Speciation

Reproductive Isolation

Two Types

Postzygotic.

Rates or Tempo of Speciation Gradualism

Punctuated Equilibrium

Quick Review

Lesson 2 — Species Concepts and Speciation