09. The Biosphere, Early life & Plant diversity

Question 1

What does phylogeny propose that animals are closely related to?

Answer 1

choanoflagellates

Question 2

How are animals differentiated from choanoflagellates?

Answer 2

1. presence of persistent multicellularity
2. formation of gastrula during early development
3. Synthesis of collagen

Question 3

Symmetry in sponges

Answer 3

irregular in form with no plane of symmetry

Question 4

Symmetry in cnidarians

Answer 4

-display radial symmetry
-Enables jellyfish to move up and down water column by flexing muscles
around their bell-like bodies
-Enables sea anemones and corals to wave their ring of food-gathering
tentacles in all directions at once

Question 5

Bilateral symmetry

Answer 5

• most animals are bilaterians

- enables movement in one horizontal direction

Question 6

Key traits of sponges

Answer 6

-Body plan resembles a flower vase, with many small
pores along sides and a larger opening at the top
a. Interior surface lined by choanocytes that function
in nutrition and gas exchange
b. Mesohyl between inner and outer layers contains
some amoeba-like cells that function in skeleton
formation and dispersal of nutrients
c. No reproductive organs, but cells that migrate into
the mesohyl and differentiate as sperm or eggs
d.Gain nutrition by intracellular digestion

Question 7

Key traits of cnidarians

Answer 7

Jellyfish & sea anemones
1. Radial symmetry
2. A mouth surrounded by tentacles
armed with stinging cells
3. Closed internal gastric cavity, the site
of extracellular digestion and excretion
4. An epidermis and endodermis,
developed from a diploblastic embryo,
enclosing a gelatinous mass called the
mesoglea

Question 8

Gastrulation

Answer 8

A highly coordinated set of cell movements in which the cells of the blastoderm migrate inward, creating germ layers of cells within the embryo.

Question 9

What are the two groups bilaterian animals are divided into?

Answer 9

1. In protostomes, the blastopore becomes the mouth

2. In deuterostomes, the blastopore becomes the anus

Question 10

Lophotrochozoans

Answer 10

• make up nearly half of all animal phyla
• annelids and mollusks
• new types of locomotion, feeding, gas exchange, behavior, and reproduction

Question 11

Annelids

Answer 11

-have a cylindrical body with distinct segments
-Head has well-developed mouth and
cerebral ganglion that connects extensive
nervous system
-Digestive system extends through the
body, with specialized organs for crushing,
digesting, excreting ingested food

Question 12

Mollusks

Answer 12

• snails, clams, mussels, squids, octopuses
  -Distinguished by a unique structure
  called the mantle that plays a major
  role in breathing and excretion (shells)
  -can be separated into gastropods, cephalopods, and bivalves

Question 13

Ecdysozoa

Answer 13

-secrete a cuticle made of protein that covers
their bodies and protects their bodies from injury and drying
-molting

Question 14

Arthropods

Answer 14

• named for their jointed legs

- chitin (hard external skeleton)

Question 15

Insects are divided into…

Answer 15

those that undergo metamorphosis and those that do not

Question 16

Complete metamorphosis

Answer 16

-involves a pupal stage in which the tissues of the larvae are reorganized into a very different adult form

Question 17

Hints at early life on earth

Answer 17

-in areas with high temps and no oxygen there were prokaryotes - archaea

Question 18

Archaea

Answer 18

Archaea includes many extremophiles able
to grow & reproduce at:
• Anoxic conditions
• Temperatures as high as 122°C
• Low pH (acidic: 0-0.7)
• Highly saline
• Extreme pressures (200 atmospheres)

Question 19

Bacteria

Answer 19

• Small, single-celled organisms that lack
membrane-bound nuclei and organelles
• Remarkable successful and diverse
• Some capable of photosynthesis
• Bacteria commonly thought of as harmful

Question 20

Horizontal gene transfer

Answer 20

The transfer of genetic material between organisms that are not parent and offspring.
-complicates our phylogenetic tree

Question 21

What are the 4 major transformations in life cycle and structure characterize the evolutionary history of plants?

Answer 21

• multicellular sporophyte protected embryos
• vascular tissues
• seeds and pollen
• flowers

Question 22

Embryophytes “land plants”

Answer 22

-defined as having terrestrial ancestors, even though some are now aquatic