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Group of embryonic cells near the dorsal margins of the closing neural tube.
New adaptations are usually modifications of?
- Pre-existing genes and structures
- Ex: Paired fins and jaws
Paired fins permits?
Increased accuracy in maneuverability
Hinged jaws permits?
Gripping and slicing of food items
Who were...Earliest Gnathostome Vertebrates?
Placoderm ancestor...given rise to?
Other gill slits were?
- Modifications of skeletal rods supporting anterior gill slits
- Modifications for respiratory
Subphylum Urochordata are?
- Sea squirts
Subphylum Cephalochordata are?
Mother lays external fertilized eggs
Fertilized eggs develop internally-no food or nutriends given to child-just growing
"Live Birth"(no maternal support)
Maternal nutrition & live birth
3 "subclasses: of fish... What are they?
- 1. Subclass Actinopterygii
- 2.Subclass Actinistia
- 3.Subclass Dipnoi
Members of this phylum exhibit secondary...derived radial symmetry?
Class Amphibia are (animals)?
Protostome with chitinous exoskeleton?
Class Amphibia are?
1st terrestrial vertebrates (tetrapods)
What's the only other successful animal colonizer of land?
What was selective pressure for the amphibians?
Climate cycles of the Devonian
Amphibians, adaptive radiation: Why?
- Lack of competition
- Abundant food
- Minimal predation
Carboniferous Period called?
"Age of the Amphibians"
Amphibians remain tied to water through?
Their physiology & meramorphosis
3 extant orders of Amphibia?
- Order Urodela
- Order Anura
- Order Apoda
- ("tailed ones") salamanders
- Mostly Northern Hemisphere
- Largely temperate in distribution
- ("tail-less ones") frogs & toads
- More specialized than urodelans
- Many adaptations for survival
- ("legless ones") caecilians
- Nearly blind, burrowers
- All tropical
Major Evolutionary Breakthrough?
Amniotic Egg Permits...
Full terrestrial existence
Shelled eggs and membranes permits...
- Retention of water
- Waste storage
- Gas exchange
- Nutrient transfer
- Physical protection
Closest living relative?
3 orders of Reptilia...
- Order Squamata
- Order Crocodilia
- Order Chelonia
Order Squamata are...
Lizards and Snakes
Order Crocodilia are...
Crocodiles and Alligators
Order Chelonia (testudines) are...
Turtles and Tortoises
In what taxon did flight first evolve?
Modified scales (keratin) with multiple functions.
Flight permits exploitations (4)...
- Was aerial reconnaissance
- Access to nutritious food
During early Jurassic (~200 mya)
What extinction opened many niches for class Mammalia?
3 Major lineages of Mammalia that emerged during Mesozoic
- 1. Monotremes
Dorsal hollow nerve cord?
Developmental infolding of an ectodermal plate
Phylum Chordata is divided into 3 subphylas...
What are they?
- 1. Subphylum Urochordata
- 2. Subphylum Cephalochordata
- 3. Subphylum Vertebrata
Sister group to chordates?
Recent shared derived traits
Phyla Chordata have 4 synapomorphies... What are they?
- 1. Notochord
- 2. Dorsal, hollow nerve cord
- 3. Pharyngeal slits
- 4. Muscular post-anal tail
Deuterostome embryonic cleavage difference
- Eight-cell stage
- Radial and Indeterminate
- Grow on top of each other
- Can have identical twins
Protostome embryonic cleavage difference
- Eight-cell stage
- Sprial and determinate
- Grow spirally
Deuterostome blastopore fate
- anus develops from blastopore
Protostome blastopore fate
- Mouth develops from blastopore
Eucoelom forms by outpocketing of the archenteron (enterocoelom)
Eucoelom forms by splitting of mesoderm (schizocoelom)
2 types of Eucoeloms
Eucoelomates divide into 2 clades based on..
- Formation of eucoelom
- Fate of blastopore
- Type of cleavage
Body cavity is completely lined with mesoderm
Body cavity is NOT completely lined with mesoderm
Characteristics of coeloms
- Permits longer size
- Organ growth
- And greater complexity
- Cushion suspended organs
- Actashydrostatic skeletons
Characteristics of animals that have Bilateral Symmetry
- Dorsal, ventral, anterior, posterior
- CephalizationClustering of sense organs, ganglial fusion
- Directional locomotion, avoidance, food-getting
- Most animals : Advantageous
Characteristics of animals that have Radial Symmetry
- Meet environment from all sides
- Oral vs. aboral surface
- Sessile or planktonic
- Of the remaining animal phyla...
- Cnidarians show primitive radial symmetry
- Other phyla are primitively bilaterally symmetrical
Phylum Porifera lack true tissues
An aggregation of similarly specialized cells united in performance of particular function.
4 branching points on Animalia
- 1. Parazoa/Eumetazoa Split
- 2. Radiata/Bilateria Split
- 3. Acoelomate/Coelomate Split
- 4. Protostome/Deuterostome Split
Ontogeny Recapitulates Phylogeny
Theory that stages in organism's embryonic development correspond to stages of its evolutionary history.
Produces testable hypothesis of genealogical relationships only from recent shared derived characteristics (synapomorphies)
Employs all measurable similarities and differences in phenotypic characteristics without consideration of convergence
Names of 2 schools of Phylogeny
Category of classification
What is Phylogeny?
The evolutionary history of a species or group of species.
The study of the diversity of life (includes taxonomy & phylogeny)
What are Animals?
Multicellular, hererotrophic, eukaryotes with tissues that develop from embryonic layers
- Lack cell walls
- Structural proteins (e.g. collagen) hold bodies together
- Unique→ nervous and muscle tissues
- Most with sexual reproduction
- Diploid stage usually dominant
- Zygote undergoes cleavage→ Blastula→ gastrula embryonic germ layers
- Only animals have HOX genes that regulate development of body form
What does HOX genes do?
Control the development of different parts
How is phylogeny determined?
- By assigning a set of characteristics derived from multiple sources
- Comparative anatomy
- Comparative embryology
- Comparative biochemistry
- Comparative molecular biology
Vertebrae phylogeny derived from...
Who is Ernst Haeckel?
- He made the Biogenic Law
The animal kingdom is...
- Other words, all animal phyla share common ancestor
There are over 30 animal phyla
Kingdom Animalia may evolved from...
A colonial flagellated protistan ancestor (choanoflagellate)
Endoderm forms during...
Gastrulation via inward growth