Module 4: Geographic Variation, Speciation and Evolutionary Rates

Charles Darwin

he observed that living organisms alter their physical and anatomical structure over time in order to better adapt to changing environments

Geographical variation

variations in genetically dependent traits between populations across a species' natural geographic range.

species

a group of organisms that share similar traits and can interbreed to produce fertile offspring

Speciation

he mechanism by which new and distinct organisms emerge in the course of evolution.

Allopatric Speciation

The form of speciation caused by geographical isolation

Allopatric Speciation

A physical barrier separates the population in this case.

Parapatric Speciation

speciation in which no physical boundary separates the organisms

Parapatric Speciation

they're standing next to each other. This is caused by a drastic change in the habitat. Individuals in these areas can interbreed, but they develop different characteristics and lifestyles as a result.

Peripatric Speciation

speciation in which new species emerge from a small isolated peripheral population

Sympatric Speciation

It refers to the evolution of new species from living ancestral species in which both species remain in the same geographical area

Species

often defined as a group of individuals with similar characteristics, where they can interbreed to produce fertile offsprings

Typological Species Concept

According to this theory, there are only a finite number of different types of living organisms on Earth.

Typological Species Concept

Aristotle and Plato stated this concept in their philosophies

1954 and 1956

Cain regarded the Typological species concept as the ___ concept in these years

morphospecies concept

ain regarded the Typological species concept as the ___

essentialist species concept

As the members of the species or a taxon can be identified by their essential characteristics, a group of scientists

morphspecies

species can be distinguished from other species by their physical characteristics and classified by their morphological characteristics.

Nominalistic Species Concept

is the assumption held by Occam and his adherents that nature only creates individuals

Nominalistic Species Concept

Species are man's creation. They ignore definite existence in nature. These ideas lack a theoretical foundation.

Nominalistic Species Concept

it believes that the species have been invented to be referred to big numbers of individuals jointly.

Biological Species Concept

A new idea known as the _______ emerged in the middle of the 18th century

genus

a community of interbreeding natural populations that are reproductively separated from other such groups

Reproductive community

For the purpose of reproduction the individuals of a species recognise one another as potential mates.

Ecological Unit

The species' members differ from each other due to many attributes, but all the members cooperatively form a unit. They interact with other species as a unit in any environment.

Genetical unit

Species comprises a large, inter-communicating gene pool, although the individual is simply a non-permanent vessel comprising a small part of the contents of the gene pool for a shorter duration.

Evolutionary Species

is a lineage (an ancestral- descendant sequence of populations) evolving separately from others and with its own unitary evolutionary role and tendencies

Simpson 1961

he defined it as "an evolutionary species is a lineage (an ancestral- descendant sequence of populations) evolving separately from others and with its own unitary evolutionary role and tendencies".

Evolutionary Species

a single lineage of ancestral-descendant population which draws its identity from other such lineages and has its own evolutionary tendencies and historical fate

Wiley 1978

He stated that "an evolutionary species are a single lineage of ancestral-descendant population which draws its identity from other such lineages and has its own evolutionary tendencies and historical fate".

Taxonomic Microspecies Biological Evolutionaey Successional

different types of species

Taxonomic Species

It includes a group of morphologically similar organisms

Microspecies

The population is obtained from a single parent.

Biological Species

It includes the population that involves sexually reproducing individuals.

Evolutionary Species

It is a combination of sexually reproducing organisms, phyletic lineages and uniparental organisms

Successional Species

It includes phyletic lineages.

Geographical Isolation and Hybridisation

factors affecting speciation

Geographical Isolation

Because of geographical changes, a few members of a population become separated from the rest of the species. Later, this isolated community spreads to a new land and gradually develops into a new species with new adaptations to its climate.

Natural selection

the process through which populations of living organisms adapt and change. Individuals in a population are naturally variable, meaning that they are all different in some ways.

Genetic drift

n evolutionary change in allelic frequencies of a population as a matter of chance. It occurs in very small populations but its effects are strong.

Hybridisation

a man-made way of creating new organisms.

Zebroid

It is a hybrid cross between a male zebra (Equus quagga) and a female donkey (Equus asinus) or with any other female members of the horse family.

Liger

It is a hybrid cross between a male lion (Panthera leo) and a tigress (Panthera tigris).

Clines

provide insight into many controversial topics in ecology and evolution, such as the degree and existence of natural selection, the mechanism

cline

a gradient of a phenotypic or genetic character within a single species.

Hybrid zones

are areas where closely related species interbreed to produce admixed offspring and can be linear or mosaic in structure.