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What is a Species?

We focused on the two main species concepts:

1. Morphological Species Concept

Definition: Species are similar in their appearance

This is what is often used

2. Biological Species Concept

Definition: Two individuals of the same species interbreed with one another in the wild and produce viable and fertile young

It needs Reproductive Isolation

Pre-zygotic barriers: prevents to species to mate with each other
Post-zygotic barriers: if mating was successful the offspring is not viable or infertile

Problems with the Biological Species Concept

Fossils
Organisms with asexual reproduction
Hybrids

Examples: Mule infertile offspring from a horse and a donkey

Red Wolf fertile offspring from a coyote mother and a grey wolf father

Sibling species

Example: Carrion and Hooded Crow

Ring species

Example: Deer Mouse

Definition of a species might not be something that fits neatly in a filing cabinet (Procrustean Fallacy), but could be viewed as peaks in a constantly moving adaptive landscape.