Lecture 5- Animal Diversity I Flashcards
What do we get from gastrulation?
A germ layer and the archenteron- the early digestive system
SEQ early embryonic development
- Start with diploid zygote
- Through cleavage, enter the eight-cell stage (zygote is mitotically dividing without growth)
- From eight cell-stage, cleavage again and blastulation to form blastula. Blastula is a hollow ball of cells around blastocoel (blastocoel does not become anything).
- Process of gastrulation (inward folding of blastula) is the last step. Gastrula and germ layers are formed as a result.
What is the archenteron/where is it?
The archenteron is the tube that forms as the blastula folds inward during gastrulation.
What is the name of the bottom of the tube of the gastrula/the entry into the digestive system?
Blastopore
Where is the ectoderm?
Outside of gastrula
Where is the endoderm?
Inside of gastrula
Homeobox genes
Code for proteins that regulate expression of developmental genes, homologous in all animals
Animal Characteristics
- Heterotrophic
- Multicellular
- Extracellular matrix
- Specialized cells/tissues/organs
- Diploid-dominant
- Specific, unique development pattern
Describe symmetry vs. asymmetry in body plan of animal
Symmetry- Arrangement of body structure in relation to axis of body
Asymmetry: No plane of symmetry through body
Radial Symmetry
Any plane through longitudinal axis (sea anemone)
Bilateral Symmetry
Only 1 plane through longitudinal axis (halves)- like a lobster, most animals have this
Cephalization
Development of a head + clustering of sense organs- central nervous system and sense organs, facilitates complex movement
Bilateral Animal Axes
Dorsal/Ventral (dorsal fin= goat’s back, ventral= belly
Anterior/Posterial- front and back (goat’s front includes head, neck etc and goat’s back includes butt)
Germ Layers + when are they formed?
Concentric layers of embryonic tissue, formed during the gastrulation process of embryonic development
What are the types of germ layers (3 layers)
Ectoderm- outer layer, nervous system
Endoderm- inner layer, lines digestive tube and other organs (lungs)
Mesoderm- middle layer, everything else- muscles, skeleton, etc
Diploblasts (how many germ layers?)
Two germ layers- Endoderm and ectoderm
Triploblasts (how many germ layers?)
Three germ layers- Endoderm, ectoderm and mesoderm
Do diploblasts have body cavities?
No, only triploblasts have body cavities
What is the general term for body cavity?
Coelom- fluid-filled space between body wall and digestive tube
Name the three types of coelom morphology
- True Coelomate/Eucoelomate
- Pseudocoelomate
- Acoelomate
Structure of True Coelomate/Eucoelomate
Has ectoderm and endoderm (both outer endoderm and endoderm surrounding digestive tube)
Structure of Pseudocoelomate
Has ectoderm and only one layer of endoderm (only outer endoderm, no endoderm surrounding digestive tube)
Structure of Aceolomate
No coelom, everything is mushed together and there is no fluid-filled body cavity between gut and body wall
Explain Coelom Evolutionary history
True coelom ancestral to pseudocoelom and acoelom. Pseudocoelom and acoelom are derived traits.
Advantages of Coelom
Circulation- no longer need to be flat, hydrostatic skeleton- support and movement
3 Characteristics of classifying by body plan
- Symmetry
- Embryonic tissue layers
- Body cavity
Protostomes vs. Deuterostomes
Protostomes: (Ancestral). Spiral and determinate cleavage. Spiral (cells rotate as they divide) and determinate (set developmental fate from the beginning). The blastopore becomes the mouth, known as first mouth, protostomes develop the mouth first and the anus later in development.
Deuterostomes: (Derived). Radial and indeterminate cleavage. Radial (cells are aligned rather than rotated) and indeterminate (not locked into developmental fate). The blastopore becomes the anus, deuterostomes are known as second mouth, the mouth develops later in development.
Not positive about which was ancestral and which was derived, hypothesis
What are the three defining characteristics that separate protostomes and deuterostomes (bilateria)
- Type of cleavage
- Coelom development
- Fate of blastopore
Sister taxon of Animals
Choanoflagellates
Cambrian Explosion
- First appearance of many body plans in fossil record
- 1st evidence of hard body parts
- Many extant phyla appear, others extinct
SDT of Animals
Multicellularity, heterotrophy, extra-cellular matrix
Extracellular matrix
Proteins outside cell membrane, connect, support cells, made mostly of collagen
True or False: Animal cell walls are composed of collagen
False; animal cells do NOT have cell walls
What is the difference between fungal heterotrophy and animal heterotrophy?
Fungi digest externally whereas animals digest internally
What are homeobox genes responsible for?
Code for proteins that regulate expression of developmental genes
What is the body cavity of bilateria called?
Coelom
True or False: Protostomes have spiral cleavage and determinate development
TRUE
What does it mean for a zygote to undergo cleavage? What is the immediate result of cleavage?
A zygote undergoes mitotic divisions (cleavage) which results in the eight-cell stage embryo
What is a blastula?
An animal embryo at the early stage of development when it is a hollow ball of cells
True or False: Deuterostomes have radial cleavage and indeterminate development
TRUE
True or False: Choanoflagellates can be unicellular or multicellular
False; choanoflagellates can be unicellular or colonial - not muticellular
What is the main protein responsible for supporting the extracellular matrix?
Collagen
True or False: All opisthokonta are ancestrally heterotrophic
TRUE
True or False: Homeobox genes are homologous in all animals
TRUE
What is included in Metazoa? SDT of Metazoa?
Porifera
Cnidaria
Acoela
Echinodermata
Chordata
Platyhelminthes
Rotifera
Mollusca
Annelida
Nematoda
Arthropoda
Multicellular, heterotrophic, Extra-cellular matrix
SDT of Metazoa
Multicellular, heterotrophic, Extra-cellular matrix
What is included in Eumetazoa? SDT of Eumetazoa?
Cnidaria
Acoela
Echinodermata
Chordata
Platyhelminthes
Rotifera
Mollusca
Annelida
Nematoda
Arthropoda
“True Animals”
Tissues and symmetry
SDT of Eumetazoa
“True Animals”
Tissues and symmetry
What is included in Bilateria? SDT of Bilateria?
Acoela
Echinodermata
Chordata
Platyhelminthes
Rotifera
Mollusca
Annelida
Nematoda
Arthropoda
Bilateral symmetry & triploblasty
SDT of Bilateria
Bilateral symmetry & triploblasty
What is included in Nephrozoa? SDT of Nephrozoa?
Echinodermata
Chordata
Platyhelminthes
Rotifera
Mollusca
Annelida
Nematoda
Arthropoda
Coelom & Excretory structures
SDT of Nephrozoa
Coelom & Excretory structures
What is included in Deuterostomia? SDT of Deuterostomia?
Echinodermata
Chordata
Deuterostome development (maybe)
SDT of Deuterostomia
Deuterostome development (maybe)
What is included in Protostomia?
SDT of Protostomia?
Platyhelminthes
Rotifera
Mollusca
Annelida
Nematoda
Arthropoda
Protostome development (maybe)
SDT of Protostomia
Protostome development (maybe)
What is included in Ecdysozoa? SDT of Ecdysozoa?
Nematoda
Arthropoda
Ecdysis: molting/shedding of exoskeleton/cuticle
What is included in Spiralia? SDT of Spiralia?
Platyhelminthes
Rotifera
Mollusca
Annelida
Entirely invertebrates
Name reflects that all undergo protostome development
No specific derived morphological trait
