Classification and phylogeny

1. 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

2. Monera Animalia
Fungi
Plantae
Protista
Prokaryotes Eukaryotes
Metazoa
Protozoa
Heterotrophic
Autotrophic
Absorptive Ingest/digest

3. 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.

4. •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.

5. 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.

6. 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

7. Natural selection: Trinidadian guppies

8. Sexual Dimorphism: the sexes differ
morphologically
Some Problems with the Typological Species
Concept
Sailfin molly
female
male

9. Alternative morphs:
e.g. horn polymorphisms in
beetles
Some Problems with the Typological Species
Concept
Hornless
morph
Horned
morph

10. Cline: a change in in morphology along
an environmental gradient
Some Problems with the Typological Species
Concept
Size in yarrow

11. Some Problems with the Typological Species
Concept
Latitude
Drosophila
subobscura

12. Cryptic species: some species are similar
morphologically but differ in other important ways
Some Problems with the Typological Species
Concept
Western
meadowlark
Eastern
meadowlark

13. 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.

14. 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…

15. Western meadowlark Eastern meadowlark

16. Mechanisms of reproductive isolation:
1. Prezygotic barriers: prevent mating or
fertilization
•Behavioral

17. Western meadowlark Eastern meadowlark

18. Mechanisms of reproductive isolation:
1. Prezygotic barriers: prevent mating or
fertilization
•Behavioral
•Temporal

19. Western spotted skunk:
summer breeder
Eastern spotted skunk:
winter breeder

20. Mechanisms of reproductive isolation:
1. Prezygotic barriers: prevent mating or
fertilization
•Behavioral
•Temporal
•Habitat isolation

21. Aquatic garter snake Terrestrial garter snake

22. Mechanisms of reproductive isolation:
1. Prezygotic barriers: prevent mating or
fertilization
2. Postzygotic barriers: prevent hybrid from
developing into a viable, fertile adult

23. 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?

24. •Bdelloid Rotifers haven’t
reproduced sexually for > 80 million
years- each individual is
reproductively isolated !
•An estimated 2000 species are
completely asexual.

25. 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

26. •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?

27. 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).

28. Carolus Linnaeus (1707- 1778)
•Swedish botanist
•Systema Naturae: a classification
scheme that used morphology to
group organisms into hierarchical
categories
Taxonomy

29. 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

30. Linnaean Classification: an example
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Piciformes
Family: Picidae
Genus: Melanerpes
species: carolinus
Taxonomy

31. Linnaean Classification: another example
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Piciformes
Family: Picidae
Genus: Melanerpes
species: erythrocephalus
Taxonomy

32. Linnaean Classification: another example
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Piciformes
Family: Ramphastidae
Genus: Ramphastos
species: sulfuratus
Taxonomy
Keeled toucan

33. Linnaean Classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Mammalia
Subclass: Eutheria
Order: Primates
Suborder: Anthropoidea
Family: Pongidae
Subfamily: ~
Genus: Gorilla
species: gorilla
Taxonomy

34. 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

35. Systematics
Phylogeny: an evolutionary tree that depicts the
relationships between living and extinct species (or
higher taxonomic groups)
A C
B 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

36. What kind of information is used to construct
phylogenies?
•Characters: organismal features that vary among
species (morphological or molecular characteristics)
Systematics

37. 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

38. sponges
jellyfish,
corals, etc.
other
animals
cellular
level
tissue
level
organ
level

39. 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:

40. 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

41. sponges
jellyfish,
corals, etc.
other
animals
asymmetrical
radial
symmetry
bilateral
symmetry

42. Characters used to construct phylogenies
•The presence of different body structures
•Developmental patterns
•Molecular data: DNA / RNA sequence data

43. 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)

44. Examples of homologous characters: Vertebrate
forelimbs

45. •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.

46. Examples of analogous characters: bat wings and
insect wings
Bat wing Fly wing

47. 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).