Announcements:

1. Labs meet this week

2. Lab manuals have been ordered

3. Some slides from each lecture will be on the web

4. Study questions will be posted after each lecture

Monera AnimaliaFungiPlantaeProtista

Prokaryotes Eukaryotes

MetazoaProtozoa

HeterotrophicAutotrophic

Absorptive Ingest/digest

What is an Animal ?

1. Animals are multicellular, heterotrophic, eukaryotes that ingest and digest their food.

2. Animals lack a cell wall.

3. Are capable of moving (during some point in their lives).

4. All animals have regulatory genes called Hox genes.

•To date > 1.5 million species of animals have been described by biologists

• ~ 10, 000 new species are described each year

•Estimates of the total number of animal species are around 10 million.

What is a Species?

Species Concepts:

1. Typological species concept: species are distinct, unchanging entities defined by unique, morphological features. This concept has been abandoned by biologists.

It ignores evolution: species are not “unchanging entities”

Some Problems with the Typological Species Concept

1. Artificial selection: artificial selection for oil content in corn

High oil

Low oil

Natural selection: Trinidadian guppies

Sexual Dimorphism: the sexes differ morphologically

Some Problems with the Typological Species Concept

Sailfin molly

femalemale

Alternative morphs:

e.g. horn polymorphisms in beetles

Some Problems with the Typological Species Concept

Hornlessmorph

Hornedmorph

Cline: a change in in morphology along an environmental gradient

Some Problems with the Typological Species Concept

Size in yarrow

Some Problems with the Typological Species Concept

Latitude

Drosophila subobscura

Cryptic species: some species are similar morphologically but differ in other important ways

Some Problems with the Typological Species Concept

Western meadowlark

Eastern meadowlark

What is a species?

Species Concepts:

2. Biological species concept: a species is a population or group of populations that can potentially interbreed and produce viable,fertile offspring, but that is reproductively isolated from other populations.

There is tremendous morphological variation within Homo sapiens. But all humans can potentially interbreed.

In contrast, some species are very similar morphologically but can not interbreed…

Western meadowlark Eastern meadowlark

Mechanisms of reproductive isolation:

1. Prezygotic barriers: prevent mating or fertilization

•Behavioral

Western meadowlark Eastern meadowlark

Mechanisms of reproductive isolation:

1. Prezygotic barriers: prevent mating or fertilization

•Behavioral

•Temporal

Western spotted skunk: summer breeder

Eastern spotted skunk: winter breeder

Mechanisms of reproductive isolation:

1. Prezygotic barriers: prevent mating or fertilization

•Behavioral

•Temporal

•Habitat isolation

Aquatic garter snake Terrestrial garter snake

Mechanisms of reproductive isolation:

1. Prezygotic barriers: prevent mating or fertilization

2. Postzygotic barriers: prevent hybrid from developing into a viable, fertile adult

Some problems with the biological species concept:

1. It is hard to apply especially to fossil data.

2. Species exist in time and space: the biological species concept has no time component.

3. What do we do with asexual organisms?

•Bdelloid Rotifers haven’t reproduced sexually for > 80 million years- each individual is reproductively isolated !

•An estimated 2000 species are completely asexual.

Species Concepts:

1. Typological species concept

2. Biological species concept

3. Evolutionary species concept• Incorporates time

4. Ecological species concept• Incoporates niche

5. Phylogenetic species concept• Incorporates unique, evolved traits

These have all been proposed to solve some of the problems of the other concepts

•To date > 1.5 million species of animals have been described by biologists

• ~ 10, 000 new species are described each year

•Estimates of the total number of animal species are around 10 million.

•How do biologists organize all of this diversity?

Classification and Phylogeny of Animals

•Taxonomy: the branch of biology that deals with the systematic classification and naming of species (or groups of species) (long pre-Darwinian history).

Carolus Linnaeus (1707- 1778)

•Swedish botanist

•Systema Naturae: a classification scheme that used morphology to group organisms into hierarchical categories

Taxonomy

Linnaean Classification

Kingdom

Phylum

Class

Order

Family

Genus

species

•In this scheme the major categories are called taxa

•Higher taxa are increasingly inclusive

•Each species is given a unique binomial name: Binomial nomenclature

Taxonomy

Linnaean Classification: an example

Kingdom: Animalia

Phylum: Chordata

Class: Aves

Order: Piciformes

Family: Picidae

Genus: Melanerpes

species: carolinus

Taxonomy

Linnaean Classification: another example

Kingdom: Animalia

Phylum: Chordata

Class: Aves

Order: Piciformes

Family: Picidae

Genus: Melanerpes

species: erythrocephalus

Taxonomy

Linnaean Classification: another example

Kingdom: Animalia

Phylum: Chordata

Class: Aves

Order: Piciformes

Family: Ramphastidae

Genus: Ramphastos

species: sulfuratus

Taxonomy

Keeled toucan

Linnaean Classification Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Class: Mammalia

Subclass: Eutheria

Order: Primates

Suborder: Anthropoidea

Family: Pongidae

Subfamily: ~

Genus: Gorilla

species: gorilla

Taxonomy

Classification and Phylogeny of Animals

•Taxonomy: the branch of biology that deals with the systematic classification and naming of species (or groups of species) (long pre-Darwinian history).

•Systematics: the branch of biology that seeks to understand the evolutionary relationships between groups of organisms (post-Darwinian).

-One of the major goals of systematics is the construction of phylogenies

Systematics

Phylogeny: an evolutionary tree that depicts the relationships between living and extinct species (or higher taxonomic groups)

A CB D

Most recent common ancestor of C and D

Most recent common ancestor of A and B

Most recent common ancestor of A, B, C and D

What kind of information is used to construct phylogenies?

•Characters: organismal features that vary among species (morphological or molecular characteristics)

Systematics

Morphological characters used to construct phylogenies-

•Levels of organization:

1. Cellular level: an aggregation of cells that are functionally differentiated, but that are not organized into tissues

2. Tissue level: cells are organized into tissues that have a specific function

3. Organ level: tissues are aggregated into organs that have specialized functions

spongesjellyfish, corals, etc.

other animals

cellularlevel

tissue level

organ level

Morphological characters used to construct phylogenies

•Type of symmetry: the arrangement of body structures relative to some axis of the body

1. Asymmetrical:

2. Radial symmetry:

3. Bilateral symmetry:

Asymmetrical

Bilateral

Radial

No plane can divide the body into two symmetrical halves

> 1 plane can divide the body into two symmetrical halves

1 plane divides the body into two symmetrical halves

sponges

jellyfish, corals, etc.

other animals

asymmetrical

radial symmetry

bilateral symmetry

Characters used to construct phylogenies

•The presence of different body structures

•Developmental patterns

•Molecular data: DNA / RNA sequence data

What kind of information is used to establish these relationships?

•Characters: organismal features that vary among species (morphological or molecular characteristics)

•Homologous characters: characters that are similar to one another due to shared ancestry (not necessarily shared function)

Examples of homologous characters: Vertebrate forelimbs

•Analogous characters: characters that are similar to one another in function, but not ancestry.

•Analogous characters are not useful in determining the evolutionary relationships between organisms.

Examples of analogous characters: bat wings and insect wings

Bat wing Fly wing

Classification and Phylogeny of Animals

•Taxonomy: the branch of biology that deals with the systematic classification and naming of species (or groups of species) (long pre-Darwinian history).

•Systematics: the branch of biology that seeks to understand the evolutionary relationships between groups of organisms (post-Darwinian).