Lecture 16-17

Question 1

Criteria for Species Concept

Answer 1

Biological Reality
Objectivity
Predictability
Reproducibility
Operational
Define a Fundamental Unit of Evolution
Wide Range Applicability

Question 2

Nominalist Species Concept

Answer 2

Species do not exist in nature, only individuals exist
Advantage: Operational
Disadvantage: Ignores a fundamental unit of evolution, Reality

Question 3

Typological Species Concept

Answer 3

Species are fixed entities, and variation is simply an incomplete manifestation of the “eidos”
Advantage: Stable classification
Disadvantage: Ignores variation, reality

Question 4

Biological Species Concept

Answer 4

A species is a group of actually or potentially interbreeding natural populations that is reproductively isolated from other such groups
Reproductive community: members of one species cannot mate with another and produce viable offspring-integrity of the community is protected by isolating mechanisms
Ecological unit: all members of biological species fill the same niche and interact as a unit with other species that share the common environment
Genetic unit: all individuals are genetically compatible and share in the free exchange of genetic material throughout the pool
Reproductive isolating mechanisms: mechanisms that retain the reproductive integrity of the species
Advantages: deals with populations, not individuals; variation is accounted for; incorporates genetics; is not based upon morphological descriptions; mechanism for speciation
Disadvantages: asexual species/lateral gene transfer not accounted for; allopatric distributions of identical species; operationality; authoritarianism; circularity confounds process with pattern; hybrid swarms/ring species

Question 5

Evolutionary Species Concept

Answer 5

An evolutionary species is a single lineage of ancestor-dependent poulations which maintains its identity from other such lineages and which has its own evolutionary tendencies and historical fate.
Evolutionary Tendencies: free to evolve differently from their sister species; evolve or not, disperse or not, go extinct or not
Advantage: Wide scale applicability; temporal component; attempts to take into account phylogeny
Disadvantage: Evolutionary tendencies is vague; measure historical fate; operationality

Question 6

Ecological Species Concept

Answer 6

Based on competitive exclusion (only one species can fill one niche); definition of the niche = definition of the species
Advantage: defined without reference to the organisms; reduces total numbers of species
Disadvantage: defined without reference to the organism; defining what is a niche can be as difficult as defining a species; niche stability; operationality; is there a one to one correspondence of niche and species

Question 7

Phylogenetic Species Concept

Answer 7

An irreducible cluster of organisms, diagnosably distinct from other such clusters, within which there is a potetial pattern of ancestry and descent
Distinguishable traits (variable feature within a group) from characters (invariant feature within a group)
Advantage: brood applicability: sexual and asexual; operational; pattern based
Disadvantage: distinguishing characters from traits; a priori knowledge of what a population is; creates a huge number of species