1 Week 1 Principle of Microbial Diversity.pptx

Species concept

Approaches to define how we identify species and

how species function in nature.

There are four main types of species concept.

1. Biological species concept

2. Morphological species concept

3. Ecological species concept

4. Phylogenetic species concept

Biological species concept

A group of organisms that can interbreed and produce viable, fertile

LIMITATIONS

•cannot be applied to asexual & fossils. & for the organisms about which little known regarding their reproduction like prokaryotes, amoeba, and some animals, plants, and fungi

Ecological species concept

Defines species based on ecological niche and resource competition.

Phylogenetic species concept

Defines species based on shared common ancestry.

Prokaryotes

Single-celled organisms without a defined nucleus or membrane-bound organelles.

Bacteria

Prokaryotic organisms with diverse shapes and cosmopolitan distribution.

Strains

A subset of a bacterial species differing from other bacteria of the same species by some minor genetic differences and distinct functions.

Species fusion theory

Formation of new hybrid species from pre-existing species.

Cladogenesis

Budding of one or more species from a parent species.

Macroevolution

Evolutionary change at the level of new taxonomic groups.

Reproductive isolation

Barriers between species that prevent viable fertile offspring.

Postzygotic mechanisms

Mechanisms that occur after fertilization.

Temporal isolation

Isolation between species due to breeding at different times.

Habitat isolation

Isolation between species due to occupying different habitats.

Behavioral isolation

Isolation between species due to different courtship rituals.

Mechanical isolation

Isolation between species due to structural differences preventing mating.

Gametic isolation

Isolation between species due to sperm being unable to fertilize eggs.

Reduced hybrid fertility

Mechanism that results in hybrids being sterile.

Hybrid breakdown

First-generation hybrids are viable and fertile, but offspring of hybrids are feeble or sterile.

Endosymbiotic theory

Theory that mitochondria and chloroplasts in eukaryotic cells evolved from symbiotic relationships with other organisms.

Gradual speciation

The divergence of populations of a single species to the point of becoming distinct species.

Allopatric speciation

Speciation that occurs due to geographic separation.

Sympatric speciation

Speciation that occurs without geographic separation.

Adaptive radiation

Rapid diversification of a common ancestor into many new species.

Hybrid zones

Areas where genetically differentiated forms or species come into contact and hybridize.

Introgression

The movement of genes between species or populations through backcrossing.

Horizontal gene transfer

The transfer of genes between organisms of different species or kingdoms.

Transformation

A type of horizontal gene transfer in bacteria.

Transduction

Another type of horizontal gene transfer in bacteria.

Conjugation: