rapid specification in snails and nematodes

Question 1

what happens during fertilization

Answer 1

sperm and egg create a zygote with a new genetic blueprint

Question 2

what happens during cleavage

Answer 2

rapid cell division
increases cell number but not the size

Question 3

what happens during axis formation

Answer 3

establishment of body plan
timing and mechanism may vary among species, some during oocyte formation, cleavage, or gastrulation

Question 4

types of axes (3)

Answer 4

dorsal-ventral
anterior-posterior
left-right symmetry

Question 5

three layered structure (germ layers) formed in gastrulation

Answer 5

endoderm (inner layer)
mesoderm (middle layer)
ectoderm (outer layer

Question 6

what is the dorsal-ventral axis and factors establishing it

Answer 6

back-belly
gravity and sperm entry point

Question 7

what is the anterior-posterior axis and what type of molecules form them

Answer 7

head-tail
signaling molecules from the dorsal region of the blastopore

Question 8

what is the left-right symmetry and what are the molecules and genes involved in its formation

Answer 8

asymmetry
molecules and genes involved in bilateral symmetry

Question 9

what happens during the primary organ formation

Answer 9

differentiation of the germ layers into tissues and organs

Question 10

what happens during organogenesis

Answer 10

further development of organs from the tissues

Question 11

what is a zygote

Answer 11

fertilized egg

Question 12

what happens during gastrulation

Answer 12

dramatic cell arrangement
establishes body axes
formation of 3 germ layers

Question 13

what is a blastopore

Answer 13

mouth-like opening in the archenteron

Question 14

what determines the coiling direction of snails

Answer 14

axis formation or during cleavage and gastrulation, specifically during the formation of left-right symmetry

Question 15

azz

Question 16

species used for studying development due to ease of lab maintenance

Answer 16

model organisms

Question 17

when and how does cell fate determination happen

Answer 17

during cleavage and gastrulation, embryonic cells acquire their specific functions

Question 18

what are eukaryotic organisms and to what do they divide into

Answer 18

has a nucleus and distinct chromosomes (genetic material) that undergo cell division (mitosis)
- multicellular eukaryotic organism
- metazoan

Question 19

what are multicellular eukaryotic organisms

Answer 19

cells from mitosis stay together, forming a complete organism (plant, fungus, or animal)

Question 20

what are metazoans

Answer 20

(animals) defined by undergoing gastrulation - which further leads to the formation of body axes

Question 21

how many animal development pathways are there

Answer 21

35 metazoan phyla: 35 animal development pathways (not linear)

Question 22

how does mitosis happen

Answer 22

cell divison that creates new cells with identical genetic material

Question 23

(basal animal key points) what are dipoblasts

Answer 23

animals with two germ layers (endoderm and ectoderm) with little to no mesoderm
- ex. cnidarians (jellyfish) / ctenophores (comb jellies)

Question 24

(basal animal key points) what does ectoderm develop into

Answer 24

outer layer - skin, nervous system

Question 25

(basal animal key points) what does mesoderm develop into

Answer 25

middle layer - muscles, bones, connective tissues

Question 26

(basal animal key points) what does endoderm develop into

Answer 26

inner layer - lining of digestive tract

Question 27

(basal animal key points) info

Answer 27

Recent studies suggest Ctenophores, not sponges, are the most ancient animal group. (Cnidarians having the oldest lineage is still debated)

Question 28

(basal animal key points) info (challenges for traditional distinctions)

Answer 28

(1) Sponges have genes for a nervous system, but lack one, suggesting it was lost in their evolution. (2) Some Cnidarians might have a form of mesoderm and exhibit bilateral symmetry in certain life stages, challenging the traditional distinction between diploblasts and triploblasts.

Question 29

(basal animal key points) what gives rise to organs and tissues

Answer 29

germ layers

Question 30

(basal animal key points) characteristics of animals that gives them a left and right side that are mirror images of each other

Answer 30

bilateral symmetry

Question 31

(basal animal key points) traits evolving independently in different lineages

Answer 31

evolutionary divergence

Question 32

(animal body plans distinction) traditional: what are the characteristics of dipoblasts - cnidarians and ctenophores (3)

Answer 32

(1) Radial symmetry (body parts arranged around a central axis) (2) Two germ layers (ectoderm & endoderm) (3) No mesoderm

Question 33

(animal body plans distinction) traditional: what are the characteristics of tripoblasts - all other animals (3)

Answer 33

(1) Bilateral symmetry (left-right mirror image) (2) Three germ layers (ectoderm, mesoderm, endoderm) (3) Mesoderm forms muscles, bones, etc.

Question 34

(tripoblastic animals) advantages of having a mesoderm (2)

Answer 34

mobility: supported by muscles body size: mesoderm gives rise to a circulatory system which supports larger bodies

Question 35

(tripoblastic animals) what are the two main branches of tripoblastic animals

Answer 35

protostomes deuerostomes

Question 36

tripoblastic animals that forms the mouth first during gastrulation

Answer 36

protostomes ex. mollusks (snails), arthropods (spiders)

Question 37

how does the coelom of protostomes form

Answer 37

schizocoely - develops from a solid mass of mesoderm cells hollowing out

Question 38

what are the two main branches of protostomes

Answer 38

(ecdysozoans) - to shed / arthropods, nematodes (molt their external skeletons) (lophotrochozoans) characterized by spiral cleavage, trochophore larva (free-swimming larval stage with cilia), and lophophore (feeding structure in some adults / ex. clams)

Question 39

what does planktonic mean

Answer 39

living in open water and drifting with the currents

Question 40

tripoblastic animals that forms the anus first during gastrulation

Answer 40

deuterostomes ex. chordates (humans, fish, frogs), echinoderms (starfish, sea urchins)

Question 41

how does the coelom of deuterostomes form

Answer 41

enterocoely - pouches from the gut extend to form the body cavity

Question 42

what features do chordates and vertebrates share (2)

Answer 42

notochord pharyngeal arches

Question 43

what are notochords

Answer 43

a rod-shaped a that precedes the development of the backbone

Question 44

what are pharyngeal arches

Answer 44

structures in developing embryos that eventually form parts of the head and neck

Question 45

what are maternally active genes

Answer 45

genes in the egg that are inherited from the mother and influence development before the zygote's genes are activated.

Question 46

what are blastomeres

Answer 46

cells formed by cleavage

Question 47

the classification of deuterostomes and protostomes is based on ____________

Answer 47

embryonic development

Question 48

(snails as devbio model) why are snails longstanding model organisms?

Answer 48

abundance easy lab maintenance variation rapid development and cfd

Question 49

(snails as devbio model) mosaic development of snails (2)

Answer 49

(1) early blastomere removal leads to missing adult structures (2) cells responsible for specific organs are highly localized

Question 50

differentiate autonomous and regulative development

Answer 50

autonomous: cfd is predetermined and removing a cell early results in a missing structure regulative: cells can compensate for the loss of neighboring cells, adjusting their fates

Question 51

characteristics of snail embryo cleavage

Answer 51

(1) spiral cleavage (planes are not straight, but at oblique angles (2) blastomeres are packed tightly together like bubbles (3) fewer cell divisions before gastrulation

Question 52

(snails as devbio model) cfd of blastomeres

Answer 52

predetermined (mosaic development)

Question 53

(snails as devbio model) characteristics during blastula stage

Answer 53

early embryo with a hollow center (blastocoel) blastocoeal are absent or very small - called stereoblastulae

Answer 54

cleavage

Answer 55

gastrula