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
Prokaryotes
Eukaryotes
Protozoa
Autotrophic
Metazoa
Heterotrophic
Absorptive
Monera
Protista
Plantae
Fungi
Ingest/digest
Animalia
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.
Some Problems with the Typological Species
Concept
It ignores evolution: species are not “unchanging
entities”
1. Artificial selection:
artificial selection for oil
content in corn
High oil
Low oil
Natural selection: Trinidadian guppies
Some Problems with the Typological Species
Concept
Sexual Dimorphism: the sexes differ
morphologically
male
female
Sailfin molly
Some Problems with the Typological Species
Concept
Alternative morphs:
Hornless
morph
Horned
morph
e.g. horn polymorphisms in
beetles
Some Problems with the Typological Species
Concept
Cline: a change in in morphology along
an environmental gradient
Size in yarrow
Some Problems with the Typological Species
Concept
Drosophila
subobscura
Latitude
Some Problems with the Typological Species
Concept
Cryptic species: some species are similar
morphologically but differ in other important ways
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).
Taxonomy
Carolus Linnaeus (1707- 1778)
•Swedish botanist
•Systema Naturae: a classification
scheme that used morphology to
group organisms into hierarchical
categories
Taxonomy
Linnaean Classification
Kingdom
•In this scheme the major
categories are called taxa
Phylum
Class
Order
Family
Genus
species
•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
Keeled toucan
Genus: Ramphastos
species: sulfuratus
Taxonomy
Linnaean Classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Mammalia
Subclass: Eutheria
Order: Primates
Suborder: Anthropoidea
Family: Pongidae
Subfamily: ~
Genus: Gorilla
species: gorilla
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
Most recent common
ancestor of A and B
B C
D
Most recent common
ancestor of C and D
Most recent common
ancestor of A, B, C
and D
Systematics
What kind of information is used to construct
phylogenies?
•Characters: organismal features that vary among
species (morphological or molecular characteristics)
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
sponges
jellyfish,
corals, etc.
other
animals
organ
level
tissue
level
cellular
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
No plane can
divide the body
into two
symmetrical halves
Bilateral
Radial
> 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
bilateral
symmetry
radial
symmetry
asymmetrical
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).