Chapter 15 - Speciation and Phylogeny Flashcards
Speciation
Occurs when the population has changed enough that it diverges from a present species to become a new species.
What are the 4 definitions of species?
- Biological species concept
- Morphological species concept
- Ecological species concept
- Phylogenetic species concept
The biological species concept
Defines a species as:
A group or population, whose members have the potential to interbreed and produce fertile offspring.
The morphological species concept
Defines a species as:
A group or population that have the same physical traits such as size, shape, and appearance
(This concept has been used to classify most the species we have)
The ecological species concept
Defines a species as:
A group or population that have the same ecological niches.
Ecological niche = the role and organism or population plays within an ecosystem.
The phylogenetic species concept
Defines a species as:
The smallest group of individuals that share a common ancestor (and form one branch on the tree of life)
Phylogeny
The evolutionary history of a species, or group of related species.
Determined by comparing morphologies, and DNA sequences between organisms
Reproductive barriers
Prevents closely related species from producing viable offspring.
(ex. a horse and a donkey)
2 types:
1. Prezygotic - occurs before fertilization takes place.
2. Postzygotic - occurs after fertilization takes place
What are the 5 prezygotic barriers?
- Habitat isolation
- Temporal isolation
- Behavioural isolation
- Mechanical isolation
- Gametic isolation
Habitat isolation
A prezygotic barrier
When two species live in the same area, but in different habitats that rarely ever encounter each other.
Temporal isolation
A prezygotic barrier
When organisms breed at different times of the day, seasons, or year.
Behavioural isolation
A prezygotic barrier
When the two species have different mating rituals so they don’t understand each others mating signals.
Mechanical isolation
A prezygotic barrier
When the reproductive parts of two species don’t fit or align.
Gametic isolation
A prezygotic barrier
When the sperm of one species may not be able to fertilize the egg of another species.
What are the 3 postzygotic barriers?
- Reduced hybrid viability
- Reduced hybrid fertility
- Hybrid breakdown
Reduced hybrid viability
A postzygotic barrier
When most hybrid offspring do not survive (they die before making it through the embryonic stage)
Reduced hybrid fertility
A postzygotic barrier
When a hybrid offspring survives, but they may not be able to reproduce.
Ex. Horse + donkey = sterile mule
Hybrid breakdown
A postzygotic barrier
When hybrid offspring can mate successfully with their parent species, or another hybrid, but their offspring are not successful.
Allopatric speciation
When groups from an ancestral species evolve into separate species, due to a period of geological separation (such as a lake or mountain range)
Sympatric speciation
The splitting of an ancestral species, into two or more reproductively isolated species without geological separation
Punctuated equilibria
A term used to describe long periods of time with little change, punctuated by abrupt rapid change
Phylogeny
The history of the evolution of a species or group
(especially in reference to the lines of descent)
Convergent evolution
The evolution of similar features in different species, which can result from living in very similar environments.
Analogy
The similarity between two species due to convergent evolution rather than descent from a common ancestor
Homology
The similarity of two species due to common ancestry
Systematics
Classifies organisms and determines their evolutionary relationships
Cladistics
A type of systematics in which common descent is the primary criteria used to classify organisms by placing them into groups called clades
Shared ancestral characters
A character shared by members of a particular clade that originated in an ancestor that is not a member of the clade
Shared derived characters
A characteristic that is present in a clay due to evolution that is not seen in the ancestor
Outgroup
A taxon outside of the group of interest that is known from other evidence to be closely related to that group of interest
Ingroup
The group of taxa, whose evolutionary relationships are being determined.
(the group you’re focussed on)
Molecular systematics
Uses DNA or assessment of other molecules to assess the relatedness of certain organisms
How can we study the evolutionary history of a species?
- fossils
- homologies
- molecular systematics
