Lecture 3 Flashcards
What is biodiversity?
Biodiversity is hierarchial
- Genes
- Populations
- Species
- Communities
- Ecosystems
- Biomes
The importance of species
- Protection of natural areas is often done at the community or ecosystem level
- e.g. Wilderness Act (1964), national parks, national wildlife refuges, Marine Mammal Protection Act (1972) - however, most conservation activities focus on the species level
- e.g. Endangered Species Act (1973), Migratory Bird Treaty Act (1918) - most of our most powerful conservation imagery consists of wildlife
Defining species
Since the importance of species is integral to modern conservation, defining species becomes essential
What is Carl Linnaeus’ classification taxonomic categories?
- Taxonomic categories (think "Dear King Phillip Came Over For Good Soup"): Domain Kingdom Phylum Class Order Family Genus Species
- Intermediate categories
- e.g. superfamily, tribe, subspecies
Why is taxonomy important?
- Standardized naming system for communication
- common names:
- change through time
- vary regionally - no two species may bear the same name
- classification files must conform to the International Code of Zoological nomenclature (ICZN)
- valid name is the oldest that has been applied to it AKA generally the oldest name that have been given to an organism sticks
What is speciation?
- Speciation is the origin of two species from a common ancestral species
- speciation bridges the evolution of populations and the evolution of taxonomic diversity
- it links microevolution with macroevolution - responsible for the branching pattern of Darwin’s theory of natural selection
- different species:
- undergo independent divergence
- maintain separate identities, evolutionary tendencies, and fates
What is a species?
Literally, Latin for “kind”. There are many different definitions of species.
What is are the species concepts?
- No one definition of species works in all situations
- a species concept is useful if it:
- classifies organisms systematically
- corresponds to a discrete group of similar organisms
- helps explain how discrete clusters of organisms arise in nature
- represents products of evolutionary history
- applies to the largest possible variety of organisms - no two of these goals always coincide
- therefore, no single species concept will serve most of these purposes
What is typological notion of species?
an individual was a member of a species if it conformed to that “type”, or ideal, in fixed morphological properties
- gave rise to the morphological species concept
What is the essentialist species concept?
each species has an ideal form and certain essence - this comes from Aristotle
What are two common species concepts that have emerged?
- Phylogenetic species concept
2. Biological species concept
What is the phylogenetic species concept?
- emphasize phylogenetic history
- popular among systematists
- e.g. “an irreducible (basal) cluster of organisms diagnosably different from other such clusters, and within which there is a parental pattern of ancestry and descent”
- quote basically says - you know it’s a separate species if there is something that differentiates it from another species
- according to this definition, speciation would occur whenever a population undergoes fixation of genetic difference - even a single DNA base pair!
What is the biological species concept?
- most frequently used concept by evolutionary biologists
- “species are groups of actually or potentially interbreeding populations, which are reproductively isolated from other such groups” (Ernst Mayr, 1942)
- reproductive isolation
- hybrids may or may not be inviable or sterile
- populations do not need to be 100% isolated
What is reproductive isolation?
biological differences or geographic separation between populations that reduces gene flow between them
How many species are there?
- difficult or impossible to answer with certainty
- there are 1.5 - 2 million species currently described
- about 18,000 new species described each year
- estimates of the total number of species on Earth varies widely, but is likely 2-8 million
- the diversity is not distributed evenly across taxa or geographically - (more species are described as cryptic species and not something new)
