Definitions
Species are defined by similar morphological characteristics
Morphological Definition
What is challenge with the morphological definition of species
- Species that look similar but aren't closely related at all!
- Individuals within the species may vary wildly in appearance with each other.
Slide 1
HARE VS. RABBIT
They are two different species!
Hares are larger, faster, and have longer ears + legs.
Rabbits are smaller, fluffier, and overall "cuter".
They even have different diets and social patterns.
Known as the father of modern taxonomy
Carl Linnaeus
What is one structural difference between DNA and RNA?
Double Stranded vs. Single Stranded
T for U
Deoxyribose vs. Ribose sugars
Etc.
Groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups
Biological Definition
A challenge with the biological species definition
- Hybrids
- Single Celled Organisms (how so?)
SLIDE 2
These are two different species! The one on the left is the American alligator, and the one on the right is the crocodile.
A quote he wrote follows, "It all comes, I believe, from trying to define the undefinable".
Charles Darwin
A reason that a harmful mutation may continue to persist in a population!
- Homozygous recessive ... carriers!
- Antagonistic Pleiotropy
- Supergenes
Etc.
A single lineage of ancestor-descendent populations of organisms that maintain their identity from other such lineages and have their own evolutionary tendencies and historical fate
Evolutionary Definition
Describe how we identify if a set of organisms follows (1) of the species definitions (NOT MORPHOLOGICAL). What are some challenges?
Biological & Evolutionary/Phylogenetic
SLIDE 3
WEASEL VS. STOAT
They are different species! Stoats are bigger and have long tails with fuzzy black tips - and weasels have a shorter tail that are the same color as their body. Stoats turn white in the winter - and they have different patterns of movement.
Inbreeding
What is the difference between genetic drift and gene flow?
Drift vs. Migration
Genes are randomly fixed in a population vs. genes are introduced into a population.
A group of morphologically indistinguishable organisms that are, in fact, genetically distinct species.
Cryptic Species
- Cant observe a lineage itself... where do you draw the line?
SLIDE 4
The one on the left is a Dorper sheep, and the one on the right is a Merino sheep! These two - while looking different, are two breeds of the same species!
The subject of Peter and Rosemary Grant's Research
The Galapagos finches!
Explain what parsimony is and what it is used for!
Phylogenetic trees - are used to determine which tree is the most likely to have occurred (the least amount of trait changes). Simplest = best.
SLIDE 5
They are the same species! They are both part of the Anas Platyrhynchos species - also known as mallards! Mallards are sexually dimorphic - meaning that males and females look different from each other.