Animals 1: Sponges+Cnidarians

Question 1

What are the dominant features of animals

Answer 1

• multicellular (diploid phase) eukaryotes
• Heterotrophic
• no cell walls
• dominant diploid phase
• tissues structurally supported by collagen externally

Question 2

How do animals fit in evolutionarily

Answer 2

Found in group Unikonta

evolved from unicellular, flagellated, opisthokont ancestors

closely related to Choanoflagellates

Question 3

What is metazoan and how is it divided

Answer 3

Metazoa = animals (a monophyletic group)

classified based on:

• presence and number of tissues
• body plan/symmetry
• Embryonic origin of tissue
• presence of a body coelom

Question 4

How does the zygote develop

Answer 4

zygote undergoes cleavage as it mitosises to 8 cells

then become a blastula, which is like a hollow ball of cells

it undergoes Gastrulation when an end caves inwards

Then it develops different parts like the Archentreron (inner cavity)

endoderm (seperates Archentreron and Blastocoel (middle cavity) and ectoderm (outer wall)

blastopore = opening to Archenteron

Question 5

What are tissues, and what are the three true tissues

Answer 5

a tissue is roughly defined as a group of cells sharing similar structure and that function as a unit. Via various degress of differentiation originating from up to three types:

Ectoderm → body covering

Mesoderm → muscles

Endoderm → digestive tract

Question 6

What are the three types of symmetry

Answer 6

None : sponges

Radial: cnidarians (can be cut symmetrical in half from any angle)

Bilateral: arthropods (can be cut symmetrically along a single axis). have a front (anterior) end and rear (posterior end). along with a top (dorsal) surface, and bottom (ventral) surface.

Question 7

How does the development of the blastopore into digestive tract effect animal phylogeny

Answer 7

• does the mouth or anus develop from the blastopore
• stoma = mouth
• Proto or Deutero refer to the order of appearance during development of the eventual mouth
• Protostome develop the mouth from the blastopore ex Molluscs, Annelids
• Deuterostomes develop the anus from blastopore, ex echinoderms, chordates

Question 8

What is a Coelom

Answer 8

A body cavity that has different derivations to help classification
Some animals don’t have one

Question 9

What is the first division among animals

Answer 9

Porifera: sponges, no true tissues

Eumatazoa: ‘true animas’ have true tissues (bilaterians + cnidarians and Ctenophora)

Question 10

What is bilateral and how is it divided

Answer 10

Bilaterians: posses true tissues, bilateral symmetry (Deuterostomes + protostomes + acoela)

Deuterostomes (hemichordata, Echinodermata, Chordata)

Protostomes (Platyhelmonthes, Rotifera, Ectoprocta, Brachiopoda, Mollusca, Annelida, Nematoda, Arthropoda)

Acoela

Question 11

Where did animals come from

Answer 11

Animals arose from a unicellular flagellated Opisthokont ancestor.

Question 12

What are animals

Answer 12

Animals are multicellular, chemoheterotrophs with no cell walls but collagen supports externally

Question 13

What percent of animals are invertebrates

Answer 13

~95% of animals are invertebrates (which is ~75% of all life)

Question 14

What was the Cambrian explosion

Answer 14

The Cambrian explosion occurred ~500mya with a rapid diversification of animal life

Many new species, lineages, and body plans arose

All Major groups of animals had ancestors in the Cambrian explosion

Question 15

Why did the Cambrian explosion happen

Answer 15

Why did it happen? Hypotheses include:

• rise in atmospheric O2
• New predator-prey relationships
• Evolution of “Homeobox genes”

Question 16

How are animals classified

Answer 16

Traditional classification of animals is based on body plans and patterns of development including:

• presence and number of tissues
• Body symmetry
• Embryonic tissue origin
• Presence of a body cavity (Coelom)

Question 17

What is Porifera

Answer 17

• Sponges
• simplest animals
• don’t have any true tissues or organs
• posses a single layer of epidermal cells
• Asymmetrical and sessile (immobile)
• Obtain food through suspension (filter) feeding

Question 18

What are Choanocytes

Answer 18

Sponges have specialized cells called Choanocytes which generate water flow through the sponge using flagella and catch floating particles with a mucous coated collar
They have a cell body, then a collar which catches food, then a flagella which pushes water.

Question 19

What do sponges use to move resources?
What do they use for protection

Answer 19

• Amoebocytes assist in movement of resources among cells
• spiny spicules provide protection

Question 20

How do sponges reproduce

Answer 20

Sponges can reproduce sexually

• most are hermaphrodites
• Sperm and eggs are released into water
• Can also reproduce asexually through fragmentation

Question 21

What are Cnidarians

Answer 21

Cnidarians include Jellyfish, Corals, Hydras, Anemones

• they have both muscles and nerves
• Most are predators
• though some corals have a symbiosis with Dinoflagellates to get energy from the sun
• Most Cnidarians are marine, though some are freshwater

Question 22

What are the 2 main body plants of sponges

Answer 22

• 2 main body plans
  
  • A sessile Polyp
  • a Mobile Medusa
• Both are radially symmetrical

Question 23

what kinds of tissues do Cnidarians have

Answer 23

• Cnidarians have both an endoderm and an ectoderm
• but no mesoderm, meaning they are Diploblastic (having 2 tissues)

Question 24

What is Physalis Physalis

Answer 24

the Portuguese Man-O-War (Physalia Physalis) is a hydrozoan that lives in a colony with identical but morphologically distinct “zoids”

Question 25

What stages does a Cnidarian go through in its lifecycle

Answer 25

Fertilized Egg
Planula (larva)
Polyp
Strobila (polyp ready to bud)
Ephyra (Clone of Polyp)
Adult Medusa

Question 26

How do Cnidarians reproduce

Answer 26

Cnidarians can be either hermaphrodite or Separate sexes

Can also reproduce asexually

Question 27

How have animals evolved their tissues

Answer 27

As animals evolved they developed from 0 tissues to 3

• Sponges have no true tissues
• Cnidarians have 2 true tissues but lack the mesoderm
• All other animals have all three tissues (endo, meso, ectoderm)

Question 28

How has animal symmetry changed

Answer 28

Animal symmetry also changes

• Porifera have no symmetry
• Cnidarians have radian symmetry
• All others have bilateral symmetry (excluding adult Echinoderms)

Question 29

What is Cephalization

Answer 29

Cephalization is a trend in bilaterians where nerve tissues and sense are concentrated at one end of the body, resulting in the evolution of a head, eventually with a brain, eyes, and other senses.