(Test 2 material) Species Identification and Classification

Macroevolution

Evolutionary changes creating new species and groups of species

Species

Group of related organisms sharing a distinctive set of attributes in nature, with ~1.75 million identified

How many species are currently identified?

1.75 million species (range of species is between 5 to 50 million)

Subspecies

Distinct population within a species with minor differences

Population genetics

Study of mechanisms causing evolution: natural selection, sexual selection, migration, inbreeding, and genetic drift

What are distinguishing characteristics of species

morphological traits, reproductive isolation, molecular features, ecological factors, evolutionary relationships

Morphology

Physical characteristics of organisms, e.g., poison tree frog color 'morphs'

Drawbacks of morphology

variations in traits. there are many traits to consider

Reproductive isolation

Prevents successful interbreeding between species, e.g., diversity in damselfly penis shapes

Drawbacks of reproductive isolation

1. May be difficult to determine in nature
2. Can interbreed and yet do not
3. Does not apply to asexual species
4. Cannot be applied to extinct species

DNA barcoding (Molecular features)

Method using DNA section to identify species, e.g., comparing DNA sequences, gene order, and chromosome structure to compare between species

Why use molecular features approach

to identify similarities and differences among different populations

Drawbacks of molecular approach

might be hard to identify differences between species since for example 2% difference in genome may not be enough

Ecological niche

Unique set of habitat resources a species requires, influencing the environment and other species

drawbacks for ecological factors

ecological barriers can be difficult to measure

one example for ecological factors

some of the Galapagos finches can only be distinguished by their island habitat

evolutionary relationships

phylogenetic trees based on fossil records or DNA

Biological species concept (according to Ernst Mayr)

Defines species as individuals able to interbreed to produce viable, fertile offspring but cannot interbreed with other species

Other concepts for biological species

evolutionary lineage concept: species should be defined based on separate evolution of lineage

ecological species concept

each species occupies an ecological niche, which is the unique set of habitat resources that a species requires, as well as its influence on the environment and other species

Mechchasims that prevent interbreeding between different species

prezypotic barriers and postzygotic barriers

Prezygotic barriers

Mechanisms preventing formation of viable, fertile individuals between species before zygote formation

Postzygotic barriers

Mechanisms preventing formation of viable, fertile individuals between species after zygote formation

Taxonomy

Describing, naming, and classifying living and extinct organisms

habitat isolation (prezygotic)

geographic barrier prevents contact (i.e. finch speices among gaapagos islands)

temporal isolation (prezygotic)

reproduce at different times of the day or year

behavioral isolation (prezygotic)

behaviors important in mate choice, changes in song (western and eastern meadowlarks)

mechanical isolation (prezygotic)

size or incompatible genitalia prevents mating

gametic isolation (prezygotic)

Gametes fail to unite successfully
Important in species that release gametes into the water or air

hybrid inviability (postzygotic)

fertilized egg cannot progress past an early embryo

hybrid sterility (postzygotic)

interspecies hybrid viable but sterile

hybrid breakdown (postzygotic)

hybrids viable and fertile but subsequent generations have genetic abnormalities

examples of prezygotic barriers

habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation

Binomial nomenclature

Scientific naming system with genus and species epithet, e.g., Canis lupus for gray wolf

systematics

study of biological diversity and the evolutionary relationships among organisms, both extinct and modern

Canis lupus

Gray Wolf (Genus name: Canis always capitalizid, species name: lupus, never capitalized)