Lecture 14: Animal body and development

Question 1

Three ‘macroscopic’ kingdoms of Eukarya

Answer 1

Plantae
Fungi
Animalia (Metazoa)

Question 2

Plantae

Answer 2

photoautotrophs who fix CO2 using water and sunlight

Question 3

Fungi

Answer 3

chemoheterotropic decomposers who digest food outside their body and absorb the nutrients

Question 4

Animalia (Metazoa)

Answer 4

chemoheterotropic hunters who internalizes their food inside body for digestion

Question 5

All animals and plants are ___, as well as most fungi

Answer 5

multicellular

Question 6

From the three (Plants, Fungi, Animals) which have a cell wall?

Answer 6

• Animals don’t have a cell wall
• Plants and fungi have their cellulose and chitin cell wall, respectively, to give structural strength
• Animals secrete compounds such as collagen outside their cells for structural support

Question 7

Life cycle almost always dominated by the

Answer 7

multicellular, diploid adult phase
* Haploid multicellular form does not exist

Question 8

___ are a key feature of animals

Answer 8

Digestive Tracts
Generation of the digestive tract is central to the development of animal’s embryo

Question 9

Development of animal embryo

Answer 9

• An animal zygote initially divides by cleavage
• Cleavage: succession of mitotic cell division which is not accompanied by cell growth
• ‘Binary fission’ without increase in body size
• After multiple cleavages, the zygote becomes the blastula

Question 10

Blastula

Answer 10

has single layer of cell covering a hollow space
* The hollow space inside blastula is called the blastocoel

Question 11

Blastula undergoes __ to become a gastrula

Answer 11

gastrulation

Question 12

gastrulation

Answer 12

One end of the blastula’s surface internalizes, generating the gastrula
* Archenteron: Cavity inside the gastrula
* Blastopore: Opening into the cavity

Question 13

Surfaces of gastrula

Answer 13

Gastrula now has two different surfaces
* Ectoderm faces the environment
* Ecto: ‘outside’
* Endoderm faces the internal space, the Archenteron
* Endo: ‘inside’

Question 14

A ____ occurs in gastrula to complete the digestive tract

Answer 14

second opening

Question 15

One opening becomes the __, the other becomes the __

Answer 15

mouth
anus

Question 16

In terms of the openings in the digestive tract, how do humans develop?

Answer 16

Humans are Deuterostomes, our blastopore develops into the anus, the second opening develops into the mouth

Question 17

Mesoderm

Answer 17

During this development, a third layer of cells develop between the endoderm and ectoderm

Question 18

Gastrulation is the beginning of

Answer 18

cell differentiation
* Different cell layers develop into different tissues and organs

Question 19

Ectoderm develops into __

Answer 19

Skin, hair, nervous systems, jaws, teeth, germ cells, etc.

Question 20

Endoderm

Answer 20

Epithelial surfaces of digestive, respiratory, excretory and reproductive tracts, liver, etc.

Question 21

Mesoderm

Answer 21

Skeleton, muscle, circulatory systems, etc.
* Not all animals have a mesoderm

Question 22

Embryo cells in bilateral animals (including humans) undergo

Answer 22

indeterminate cleavage
*Cells at early embryonic stage are not completely- fixated by their differentiation, and can still become a whole organism if separated

Question 23

Monozygotic twins (identical twins) occur

Answer 23

when an early-human embryo is physically split into two, each developing into an independent fetus

Question 24

Dizygotic twins (fraternal twins/non-identical twins) occur

Answer 24

when two eggs are fertilized simultaneously

Question 25

Body plan

Answer 25

Very fundamental, overall shape/layout of the animal body

Question 26

Three types of symmetry

Answer 26

* Radial symmetry * Bilateral symmetry * No symmetry

Question 27

Radial symmetry

Answer 27

* Body arranged around a single axis that passes through the center of body (informally, 'top-down' axis) * Body parts radiate towards outside from this central axis * Whole body interacts with environment equally from all sides

Question 28

What type of organisms have radial symmetry

Answer 28

* Many sessile or planktonic organisms have radial symmetry * Sessile: living attached to a surface (hydra, sea anemone, etc.) * Planktonic: drifting or weakly swimming (jellyfish etc.)

Question 29

Bilateral symmetry

Answer 29

* Body parts arranged around two axes * Head-Tail (Cranial-Caudal) * Dorsal-Ventral (Anterior-Posterior) * Dorsal side is the 'back' of the animal * The two axis makes a 2-dimensional plane, dividing the animal symmetrically into their 'left side' and 'right side'

Question 30

Where do animals with bilateral symmetry tend to have their central nervous system

Answer 30

Many animals with bilateral symmetry have sensory equipment and the central nervous system at the end of the head

Question 31

No symmetry (sponges)

Answer 31

* Sponges are the basal group of the animal kingdom, who diverged first from the rest of animals * Many sponges can grow into a random shape with no obvious axis of symmetry

Question 32

Kingdom Animalia (aka Metazoa) is a

Answer 32

monophyletic clade derived from a single common ancestor

Question 33

Sponges (Porifera) were the

Answer 33

first group of animals to diverge from the rest of animalia * Sponges lack true tissues such as muscles and nerves

Question 34

Eumetazoa

Answer 34

All other non-sponge animals * All Eumetazoa have true issues

Question 35

Two groups of Eumetazoa

Answer 35

*Basal Eumetazoans generally have radial symmetry (hydra, jellyfish, etc.) * All other Eumatazoans are Bilateria, animals with bilateral symmetry

Question 36

Three major Bilateria clades

Answer 36

* Lophotrochozoa (incredibly diverse clade including clams, snails, squids, earthworms, tapeworms) * Ecdysozoa (incredibly diverse clade including crabs, spiders, nematodes, butterflies) * Deuterostomia (starfish,human)

Question 37

Most animals are

Answer 37

invertebrates (~95%)

Question 38

Part of Chordata are the only group with

Answer 38

vertebrate

Question 39

___ are sister group to eumetazoa

Answer 39

Sponges

Question 40

Sedentary suspension feeders

Answer 40

* Draws in water from their side- pores and out from the central cavity * Filters out food particles suspended in water

Question 41

Sponge body made of two cell layers, filled by the

Answer 41

mesohyl ('middle matter') * All cells have good access to water, no need for circulatory system * No highly-differentiated tissues like the eumetazoans

Question 42

___ are sister-group protists of animals

Answer 42

Choanoflagellate

Question 43

When did animals emerge as a group of organisms

Answer 43

* Molecular and fossil evidences date origin of animals back to ~710 million years ago

Question 44

Choanoflagellate relation to animals

Answer 44

* Choanoflagellates are the closest protists to animals * Choanoflagellate cells look very similar to the collar cells of sponges * Molecular analysis also places choanoflagellates beside animals

Question 45

Some Choanoflagellates such as __have proteins to stick onto other cells, forming a colony

Answer 45

Salpingoeca rosetta * S. rosetta cells also differentiates into various cell types (colonial, individually swimming, etc.) based on environmental cues

Question 46

Why are scientists studying S. rosetta?

Answer 46

Scientists are studying these organisms to investigate the origin of animal multicellularity