Origins and Patterns of Biodiversity (Bio 2e, Chapters 18-20)

Biological Species Concepts

Species are groups of actually or potentially interbreeding individuals that can mate and produce fertile offspring

Phylogenetic Species Concepts

A species is the smallest set of organisms that share a common ancestor, and can be distinguished from other such sets.

Morphological Species Concepts

Species are collections of living organisms that have some morphological and biochemical traits in common.

Ecological Species Concepts

A species is a set of organisms, adapted to a set of resources, called a niche, in the environment.

Biological Species Concept Author 

This idea was promoted by Ernst Mayr, an evolutionary biologist who worked on birds.

Morphological Species Concept Pros

This is what most taxonomists actually use to classify specimens and describe species.

It is expedient-it can be applied to dead specimens, and even to fossils.

Morphological Species Concept Cons

It is subjective. 

 Species with morphological variation, and complex life histories, pose problems

Phylogenetic Species Concept emphasizes what?

the species as a lineage on the tree of life.

Ecological Species Concept must be what?

a discrete lineage recognizably different from other such lineages and with a distinct evolutionary history.

Speciation

is the origin of new species. With extinction, it is one of two keystone processes of macroevolution

In speciatation what has to occur for new species to originate

reproductive isolation

reproductively isolatation 

When genetic or behavioral mechanisms evolve to keep populations of species from interbreeding

isolation mechanisms

Barriers to allele flow; without it distinct species would be impossible 

Sympatric species

live in the same place

What is this an example of?

Example of sympatric speciation: Variations of Lacewings don’t reproduce due to different mating songs

Two Isolation Mechanisms

Prezygotic, and Postzygotic

Prezygotic isolation mechanisms

biological barriers that prevent mating or fertilization between individuals of different species, occurring before a zygote (a fertilized egg) can form

Postzygotic isolating mechanisms

Act after mating; prevents fertilization or prevents hybrids from passing on their genes

Two Types of Speciation

Allopatric and Sympatric

Allopatric Speciation

Involves a geographic barrier. Physically separates populations and blocks allele flow.

Sympatric Speciation does not involve a what?

geographic barrier.

What is this?

Example of Allopatric Speciation: Two types of squirrels that underwent speciation because of the grand canyon separating the two

Sympatric Speciation results from

intrinsic factors, such as chromosomal changes and nonrandom mating

Mechanisms of Sympatric Speciation

Polyploidy, habitat differentiation, sexual selection, behavioral changes. and ecological niche specialization

Polyploidy

Condition of having more than two sets of chromosomes (3n, 4n, etc.).

Autopolyploidy

Extra chromosome sets come from one species (self-duplication).

Allopolyploidy

Extra chromosome sets come from two different species (hybridization + doubling).

What is this example of?

The Cavendish banana is an example of sympatric speciation through allopolyploidy, with Musa acuminata being one of the sexual parent species.

What is this example of?

Example of Sympatric Speciation: The apple maggot was a species that has originated via host shift. When apples were introduced to North America, a shift to apple hosts promoted sympatric speciation.

Are Hybridization between animal species considered new species

No because they are sterile 

What is this an example of? 

Example of hybridization producing sterile offspring: Edible frog was found to be a sterile frog from a mix between two other frog species 

What is this an example of?

Exception to hybridzation producing sterile offspring: two distinct parent species(infertile) producing fertile hybrids 

The Tree of Life

All organisms on Earth descend from a single, common ancestor.

What is this?

The tree of life, a diagram that represents that actual diversification of organisms from a common ancestor 

What is this?

Old Five kingdom classifcation, it does well grouping organisms based on their characteristic but doesn’t reflect evolution well

What is this?

Tree made from Karl Woese ideas on ribosomal RNA —> indicates three major domains of living things 

Domains

Three large groups of Bacteria (prokaryotes) Archaea(prokaryotes), and Eukarya (eukaryotes) 

Prokaryotic

cells lack a nucleus, Most of the true diversity on the planet is among them

Eukaryotic

cells possess a nucleus and membrane bound organelles

This group is “nested within” the Archaea.

How Many Species are Out There?

approximately 2 million or 8.7 million, though it may be much higher depends on which definition is used

Polling Question:  Which of the following taxonomic groups has the LARGEST proportion of UNDESCRIBED species?

Beetles

Biodiversity encompasses what?

The genetic diversity within populations, communities and ecosystems, and diversity of species or lineages

What is this an example of? 

Example of Biodiversity: It originated from a single species and now have 7500 varieties with each their own distinct characteristic allele pool 

Taxonomic Diversity

The different number of species an ecosystem habitat or location contains

Living things are organized into what?

communities and ecosystems

What is this? 

An example of communities forming from human cultural practices: In this place it was grazed by humans and harbor unique organisms that are connected to their interactions with humans 

What are some major areas of unexplored biodiversity 

Tropical rainforests, ocean floor, microbial world

Global Biodiversity Patterns

Latitudinal gradient, Broad, geographical realms determined by history

Latitudinal Gradient

biodiversity increases from the poles to the tropics

Four Factors that determine Geographical range of species

History, Biological Tolerances, Other Species, a combination of the above

Examples of Physiological Factors Limiting Distribution

Palm trees cannot handle the cold so they stick to the tropics and sub tropics 

What determines Local Biodiversity

Ecological Niches

Generalist species

Have a broad niche

Specialist species

Narrow niche, more extinction prone under changing environmental conditions

What is this 

An example of generalists and specialists 

Phylogeny

a group is a “family tree” describing how species are related.  The branching pattern of different groups of organisms is caused by repeated cladogenesis

Systematics

is the study of phylogeny

Taxonomy

process of describing and naming organisms

What is this

An example of Adaptive Radiation - a single common ancestor rapidly evolves into multiple new species

What is a goal of Systematics

define the tree of life in terms of ordered, monophyletic groups.

monophyletic group

is all the descendants of a common ancestor

Polyphyletic groups

do not share a common ancestor.

Paraphyletic groups

have a common ancestor, but exclude some taxa.

Cladogenesis

the origin of lineages, is the formation of a new branch on the tree of life. Caused by speciation 

Homology

A trait or character state is homologous in two or more different species if they all inherited that trait from their common ancestor.

cladogram

a pattern of loss and acquisition of characters, and the subsequent passing-down of these traits to descendent species

Synapormorphy

derived trait that a group has inherited because the common ancestor of that group had a derived characteristic and passed it on.

Synplesiomorphy

an evolutionarily primitive trait that a group has inherited because the common ancestor of that group had inherited the primitive condition, unchanged, from an earlier group.

What is this?

An example of homology which is a synapormorphy 

Homoplasy

When a character has evolved more than once, if possessed by two species but not present in the common ancestor

What is this?

Example of homoplasy not homology - raised from similar selective pressures

Gondwanan Distrubution

Species distribution across Southern continents of Australia, South Africa, South America, and sometimes India.

What is this?

Biogeographich realms before invasions

What biogeographic realm is North America in?

Nearctic

Convergent evolution is what?

the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.

What is this an example of?

Convergent evolution

Adaptive radiation

rapid evolution of many diverse species from a common ancestor when new ecological opportunities arise.

What is this?

An example of adaptive radiation 

Background extinction rate 

normal, baseline rate of species loss that occurs naturally over long periods of time, due to ecological and evolutionary processes (e.g., competition, predation, habitat change).

Major mass extinction events

•1) The Late Devonian

•2) Mid-Ordovician

•3) Permian-Triassic

•4) Late Triassic

5) Cretaceous-Paleogene.