Exam 3

Question 1

Describe the evidence that supports the theory that mitochondria and plastids evolved by primary (and sometimes secondary) endosymbiosis.

Answer 1

The mitochondria and plastids(basically the mitochondria of plants) both have two plasma layers; their own DNA; they have their own proteins that carry out process that sustains life; use O2 to make ATP; use fission to create new mitochondria

Question 2

Describe the evidence that suggests that mitochondria were acquired before plastids in eukaryotic evolution.

Answer 2

All eukaryotes have mitochondria but only a few have plastids.

Question 3

Define secondary endosymbiosis and explain its role in the evolution of photosynthetic protists.

Answer 3

Secondary endosymbiosis is when a larger eukaryote engulfs another eukaryote that has undergone primary endosymbiosis( the eukaryote engulfed a prokaryote to use it(prokaryote) to its(eukaryote) advantage.

Question 4

List examples of symbiosis in animals.

Answer 4

1. Sea anemones (Cnidaria) that contain zoxanthellae (dinoflagellate protists)
2. nudibranch mollusks that have photosynthetic algae on their backs.
3. spotted salamander eggs that contain green algae.
4. the origins of mitochondria and chloroplasts way back in the early history of eukaryotes.

Question 5

Describe the formation of tissue layers in embryos.

Answer 5

Tissue layers a formed through a process called gastrulation. In this process, a hollow cluster of cells forms into a blastula. The blastula then can reorganize into two primary layers: the endoderm (inner layer of tissue around the digestive tract) and the ectoderm( very outer layer of the blastopore). This blastula can form two types of organisms: Diploblastic( just endo and ectoderm) or Trophoblastic(endoderm, mesoderm, and ectoderm)

Question 6

Identify some examples of body parts/organ systems that arise from endoderm. (Likewise for ectoderm and mesoderm.)

Answer 6

Endoderm: Lining of the gastrointestinal and respiratory tract; the Liver; Epithelial lining of the urinary bladder and urethra

Mesoderm: Connective tissues, Cartilage, and Bones; the Kidneys; the Gonads(ovaries and testes)

Ectoderm: Cental Nervous System(brain and spinal cord); Epidermis(skin) and its appendages(hair and nails)

Question 7

Explain the adaptive significance and function of different symmetry patterns.

Answer 7

Radial: Usually used by stationary or slow moving organisms (such as the Cnidarians) so that they can sense what happening around them in a 360-degree motion. This type of symmetry doesn’t have a left or right side and if the organism is cut in half, the parts would look the same.

Bilateral: This type of symmetry has a left and right side and allows the organisms to sense in all directions (up, down, left, right, etc). This is advantageous to organisms that move constantly so that they can hunt prey and/or escape predators.

Question 8

Explain the significance of cephalization.

Answer 8

Cephalization is the concentration of the nervous system into one place, the head. This concentration allows for a more complex brain which leads to a more complex and intelligent organism.

Question 9

Describe how segmentation can be important in the evolution of body shape/structure/function.

Answer 9

Allows organism to duplicate organs and identical body structures, such as arms and legs. Segmentation also separates different body functions into different body systems (such as digestive, respiratory, cardiovascular, etc.)

Question 10

Discuss the advantages of a complete digestive tract.

Answer 10

1. allow for continuous intake of food

2. more efficient at absorbing nutrients than an incomplect digestive tract

Question 11

Identify the functions of skeletons and give examples.

Answer 11

1. To provide support: spinal column allows humans to stand upright
2. To provide protection: the rib cage and skull protects sensitive organs from external forces
3. To provide movement: bones along with muscle allows organisms to move

Question 12

List the characteristics (synapomorphies) of animals.

Answer 12

1. extracellular matrix containing collagen and elastin
2. multicellularity with division of labor
3. heterotrophic methods of food acquisition

Question 13

Describe the anatomy of sponges.

Answer 13

The anatomy of a sponge consists of…

1. Pores: allows water into the sponges central cavity
2. Osculum: large hole at the top of sponge where water exits
3. Choanocytes: specialized cells that filter food from water
4. Spicules: skeletal structures made of calcium carbonate (CaCO3), silicon dioxide, and proteins (they look like tiny spikes)
5. Archaeocytes: specialized cells that make spicules, digest and moves food, and carry sperm cells to eggs

Question 14

Describe the classes of Cnidaria and their body forms.

Answer 14

There are three classes of the Phylum Cnidaria.

1. Hydrozoa: Obelia (kinda looks like a polyp)
2. Scyphozoa: Jellyfish
3. Anthozoa: Coral and Sea Anemonies

Question 15

Identify the synapomorphies that define the classes of Platyhelminthes.

Answer 15

Platyhelminthes are flatworms consists of three classes:
1. Cestoda (tapeworms): Synapomorphies- body form 3 tape like regions. Has suckers and hooks. Lacks mouth and digestive system

2. Trematoda(flukeworms): Synapomorphies- possess oral and ventral suckers (no hooks). Characterized by being parasitic complete life cycle
3. Turbellaria (Planarians): Synapomorphies- highly cephalized with eye spots (ocelli), incomplete gut, and flame cells called osmoregulate (meaning that if you touch it, it will feel as though your hand it on fire

Question 16

Describe each of these basal phyla in terms of tissue layers and body cavities.

Answer 16

1. Porifera (Sponges)
   Tissue Layers: None
   Body Cavity: None (They are Acoelomates)
2. Cnidarians (Jellyfish, Coral, and Sea Anemonies)
   Tissue Layers: 2 (endo and ectoderm)
   Body Cavity: None (They are Acoelomates as well)

Question 17

Contrast the early embryology of protostomes and deuterostomes. Describe the fate of the blastopore and the origin of the mesoderm and coelom.

Answer 17

Protostomes: cells undergo spiral cleavage (2 cells wedge and twist themselves into the top of 4 other cells)
Fate- Protostomes have a determinate development, meaning that each cell already has a specialised job and if one were to split off, it would halt development( the organism dies). Blastopore becomes mouth. Mesoderm forms around the pocket of the gut.

Deuterostomes: cells undergo radial cleavage (the cells become uniform)
Fate- Deuterostomes have an indeterminate development, meaning that the cells haven’t specialised and if they were to separate, then they would just make another organism (twins!). Blastopore becomes anus. Mesoderm forms on top of the gut.

Question 18

Identify which animal phyla are protostomes, which are deuterostomes, and which are in other groups.

Answer 18

Protostomes: Lophotrochozoa and Ecdysozoa
Deuterostomes: Chordates and Echinoderms
Others: Porifera and Cnidarians

Question 19

Describe the characteristics (synapomorphies) of each class of mollusks.

Answer 19

Polyplacophora (Chitons): 7-8 shell plates; mantel fused with shell

Gastropoda (Slugs and Snails): a “head”; coiled shell; shell undergoes torsion

Bivalvia (Muscles, Clams, etc.): gills modified for filter feeding; shell in two halfs; loss of radula

Cephalopoda (Octopus and Squid): closed circular system (blood pumped by heart through blood vessels); beak mouth; siphuncle; seperate shell; tentacles and siphon; cranium; ink sac

Question 20

Describe the characteristics (synapomorphies) of mollusks.

Answer 20

Spicules/shell, mantle, muscular foot, rabula

Question 21

Describe the characteristics (synapomorphies) of annelids.

Answer 21

setae and segmentation

Question 22

Describe the characteristics (synapomorphies) of each class of annelids.

Answer 22

Polychaeta (Marine Worms): Head with sensory appendage; parapodia

Oligochaeta (Earthworms): clitellum (specialized segment of body used for reproduction); hermaphroditic(has both male and female reproductive organs); loss of trochophore

Hirudinea (leeches): same synapomorphies as the earthworms; also have posterior sucker and superficial annuli

Question 23

Describe the characteristics of arthropods.

Answer 23

1. they have a chitinous exoskeleton that they shed during growth
2. paired body parts are jointed
3. segmented body parts separated into regions (head, cephalothorax, thorax, abdomen)

Question 24

Describe the characteristics of each subphylum of arthropods.

Answer 24

Hexapoda
3 segment abdomen

Crustacea

- stalked eyes
- nauplius larva
- 2 pairs antennae

Myriapoda
-lose of compound eyes
chilopods (centipedes)
-fangs, venom

diplopods (millipedes)
-diplosegments

Chelicerata

  - chellicerae 
  - reduced # of walking legs
  - body in two segments: cephalothorax, abdomen

  Pycnogonida -water spiders
  Merostomes
       -long telson
       -book gills

   Arachnida
     -4 paired legs
     -Arachnid lungs and or book lungs
      Scorpions
           -stinger
           -pincers
      Mites & ticks
      Spiders
           -spinnerets

Question 25

Describe the general characteristics of insects.

Answer 25

Insects have an exoskeleton

Insects have three main body parts: head, thorax, and abdomen.

Insects have a pair of antennae on top of their heads.

Insects have three pairs of legs.

Question 26

Distinguish between, hemimetabolous, and holometabolous insects.

Answer 26

Hemimetabolous: incomplete metamorphosis; egg -> nymph (small version of the adult it will turn into) -> adult

Holometabolous: complete metamorphosis egg-> larva-> pupa/chrysalis-> adult(thry grows wings!)

Question 27

Compare and contrast venom and poison.

Answer 27

Venom is injected
Poison is ingested(eaten)
Both are toxic substances that could possibly kill you

Question 28

Explain the advantages and limitations of an exoskeleton.

Answer 28

Advantage: hard shell give excellent protection
Limits: limits size, energy, and leaves organism vulnerable

Question 29

Compare and contrast open vs. closed circulatory systems.

Answer 29

Open circulatory system: blood bathes organs Ex. Lobsters, Crayfish have circulatory system

Closed circulatory system: blood pumped by heart to organs via veins and capillaries Ex. Humans

Question 30

Identify synapomorphies of the Echinodermata.

Answer 30

2nd degree pentaradial symmetry.

Smart connective tissue which liquifies with neural control.

CaCO3 endoskeleton

Loss cerebral ganglia

Water vascular system with madreporite and tube feet with suckers

ambulacral zones where tube feet emerge

Question 31

Describe the unique connective tissues of echinoderms and how they can be adaptive.

Answer 31

They can liquefy their body tissues neurologically and detach their limbs in order to save the rest of the body. They also regrow these appendages. In fact, if you cut one in half they can multiply.

Question 32

Explain how Echinoderms deal with the major challenges that your skeleton deals with.

Answer 32

Protection: endoskeletal plate CaCO3 and spikes that protrude from plate
Movement: hydrostatic skeleton (water vascular system tube feet, w suckers and madreporite)
Structure: endoskeletal plate

Question 33

describe synapomorphies: each class of echinoderms

Answer 33

Echinoderms:
 Crinoidea (sea lillies)
- lack tube feet 
- No Madreporite 
- tube feet with suckers 
- oral side down

Ophithuroidea (Brittle Star)

• no anus
• articulating appendages
• madreporite
• loss of suckers

Asteroidea (the common starfish)

• gonads and guts in arms
• pedicellirae

Echinoidea (sea urchins)

• Test
• Moveable spikes
• pedicellirae
• no arms