Eumetazoa (part of animals)

Question 1

What classifies animals that are eumetazoa?

Answer 1

animals that have true tissue (integrated group of cells with a common structure, function or both that are isolated from OTHER tissues by membranous later

Question 2

What other phylum consist of eumatozoa?

Answer 2

bilateria, radiata, deuterostomia, protostomia, lophotrocozoa, and ecdysozoa

Question 3

What is a radial symmetry body plan?

Answer 3

no front and back, or left and right (like jellyfish), they can be cut into different sections and still look the same

Question 4

What are bilateral symmetry body plans?

Answer 4

two sided symmetry. They have a clear, left and right side. Just like humans

Question 5

What are two modes of embryonic development in animals (aka how the gastrula forms)?

Answer 5

1. protostomia: the first opening of the blastopore (gastrula) becomes the mouth and the second is the anus
2. Deuterostomia: the second opening of the blastopore becomes the mouth (blastopore forms the anus and then forms the mouth in opposite end)

Question 6

How do cells divide in terms of protostome development?

Answer 6

• protostome development is that each new row of cells that is added is twisted slightly off centre, and forms a spiral cleavage

Question 7

Why are protostomia determinant types of development?

Answer 7

they are determinant because each new cell is destined to form some part of the later embryo (if you remove the cells, i twill result in the embryo missing an organ)

Question 8

How do cells divid in terms of deurterostome development?

Answer 8

each cell division stacks the new cells directly above the previous ones, forming radial cleavage

Question 9

Why are deuterostomes indeterminate types of development?

Answer 9

they are indeterminate because each embryonic cells are not differentiated –> young embryo’s can split and form 2 different embryos

Question 10

What are the 3 germ layers (tissues?)

Answer 10

endoderm –> digestive tract (gut)
Ectoderm –> outer covering (skin and nerves)
mesoderm —> muscle and other organs

Question 11

What is special about the group “radiata” in terms of germ layers?

Answer 11

they have 2 embryonic cell layers and are considered to be diploblastic (only have endoderm and ectoderm)

Question 12

What is special about the group “bilateria” in terms of germ layers?

Answer 12

they have 3 embryonic cell layers (thats why they out number radiate. They are considered to be triploblastic and have an endoderm, ectoderm and mesoderm.

Question 13

what are coelom?

Answer 13

• present in most triploblastic animals that possess a fluid-filled body cavity
• a true body cavity is called a coelom and it is derived from the mesoderm
  (tissue layer lining coelom and suspending internal organs from mesoderm)

Question 14

What are coelomates?

Answer 14

they are animals that possess a true coelom

Question 15

What are pseudocoelomates?

Answer 15

triploblastic animals that lack complete mesodermal lining

- “fake” coelom

Question 16

what are acoelomates?

Answer 16

they are triploblastic animals that lack a body cavity (just giant masses of cells)

Question 17

What is the function of a coelom?

Answer 17

they cushion internal organs (act as shock proof)

• allow internal organs to shift without coming out of the body (i.e. when your guts move, or when your heart beats
• fluid filled cavities that are used as hydrostatic skeleton

Question 18

What are the 6 agreements in the old tree vs. the new tree

Answer 18

1. kingdom anamalia is a monophyletic group
2. all animals share a common ancestor that was a colonial flagellate
3. sponges are basal animals (the most ancient)
4. Eumetazoa is a clade of animals with true tissues
5. most animal phyla belong to the clade bilateria (bilateral structure where their sides differ but sides are the same)
6. Chordates belong to deuterostomia

Question 19

What are 2 major disagreements in the old tree vs. the new tree?

Answer 19

1. morphology-based tree (old tree) divides bilaterians into two clades: deurterostomes and protostomes
2. recent molecular studies indicate three bilateral clades: deuterostomia, ecdysozoa and lophotrochozoa

Question 20

approx. when did land animals arrive on earth?

Answer 20

~450 million years ago

Question 21

who resembles best the recent common ancestor of all animals?

Answer 21

choanoflagellates (heterotrophic protists with a single flagellum) surrounded by microvilli
their cell morphology was similar to sponges

Question 22

What is one hypothesis on how we went from unicellular organisms to multicellular organisms?

Answer 22

hypothesis was that single cells send signals together and clump up through adhesion, and then as they all clump up together, specific cells start specializing resulting in higher fitness.

• mutations have allowed the specialization as a group of cells may have encountered a certain mutation to make them different than another clumped cell connected to them.
• Infolding caused layers and those layers highly resemble the embryonic development

Question 23

What is the role of natural selection in the evolution of multicellularity?

Answer 23

specialization of cells can make an organism more efficient therefore they can reproduce better and survive. Cooperative aggregation of cells are able to survive better and produce more offspring than their unicellular counterparts therefore they have higher fitness, then the various evolutionary pathways could all be possible