Lec. 15 Intro to Animals

Question 1

Animals

1 How many
2 # of species
3 Where did they originate
4 What is its lineage called
5 What are its closest relatives and how long ago

Answer 1

1. How many? Between 3-10 million animals exist
2. Species:1.4 million to date
3. Originated from single celled eukaryotes
4. Occurs in lineage called Opishokonta (fungi, animals, choanoflagelletes)
5. Choanoflagelletes are closest living relatives to animals (common ancestor 900 million years ago)

Question 2

What are the key traits in which animals form a monophyletic clade

Answer 2

1. multicellular eukaryotes with no cell walls but extensive ECM (includes proteins)
2. Heterotrophs
3. Move under own power at some point in life cycle
4. Neurons that transmit electrical signals and muscle cells that change shape of body by contracting (other than sponges)

Question 3

What type of data is collected to base the origin of animals from? (4) Also what is the most ancient lineage of animals? Are animals monophyletic?

Answer 3

1. Fossils
2. Comparitive morphology (compare their structures)
3. Comparitive development (Hox genes)
4. Comparitive genomics (DNA)
   Sponges are most ancient lineage
   Yes! they are monophyletic

Question 4

Porifera (Sponges)

1. Are they a monophyletic group?
2. How do sponges have the basic toolkit need for multicelluarity?
3. Do sponges have complex tissue?
4. Do sponges have epithelium?

Answer 4

1. Sponges may be paraphyletic (contains some but not all descendants of common ancestors)
2. Cell-cell adhesion, cell-ECM adhesion, Epithelium
3. Sponges do not have complex tissue (just clump of cells)
4. Some sponges have true epitheliun layers which are essential to animal form and function

Question 5

Sponges first

What are some of the sponge “firsts” (3)

Answer 5

1. Earliest animal to appear in the fossil record
2. First sponges appeared more than 700 mya
3. Most common ancestor due to presence of multicellular sponges and absense of other multicellular organisms in fossil record

Question 6

How do sponges share characteristics with choanoflagelletes

Answer 6

1. both are bethnic (live at bottom of aquatic environments) and sessile (not freely moving)
2. Both feed using cells with nearly identical morphology
3. Trap organic debris (choanoflagelettes-flagella, sponges-choanocytes)
4. Feeding occurs at cellular level
5. Form colonies

Question 7

How do sponges differ from choanoflagelletes

Answer 7

1. Sponges contain specialized cell types that are dependent on each other (cant live as single cell). Some occur in organized layers surrounded by ECM

Question 8

Origin of embryonic tissue layers

1. Diploblasts
2. Triploblasts
3. Germ layers

Answer 8

1. Diploblasts- animals who have two types of tissues ort germ layers (Ectoderm-outside skin, Endoderm-Inside skin)
2. Triploblasts- animals whos embryos have 3 germ layers (ecotoderm-outer skin, endo-inner, meso, middle)
3. Germ layers- develop into distinct adult tissues and organs

Question 9

Deep homology and convergent evolution in diploblasts

What chracteristics are shared between diplo and triploblasts
What characteristics are missing in diploblasts

How is similarity achieved

Answer 9

Shared:
- mesoderm like cells called mesoglea, genes coding for structural components of mesodermal cells
- some can change shape of their bodies
- actin and myosin
Missing:
- Mesodermal specification genes
- Well defined mesoderm
- True muscles

Convergent evolution with deep homolgy

Question 10

Body symmetry

1. Body symmetry
2. What animals have radial symmetry
3. Which exhibit bilateral symmetry?
4. Which evolved first?

Answer 10

1. Body symmetry- key morphological aspects of animals body plans
2. Radial- cnidarians, ctenophores, sponges have 2 planes of symmetry
3. Bilateral- single plane of symmetry and long narrow bodies (humans ie and all triploblasts)
4. Radial symmetry evolved first

Cnidarians are actually biradially symetric in their internal morphology

Question 11

The action of what causes symmetry of bilaterians

Answer 11

1. Hox genes- regulate anterior-posterior axis
2. Dpp genes- regulate dorsal-ventral axis

Question 12

Body symmetry is associated with nervous system

1. How are symmetry and nervous system related in sponges?
2. What do neurons do?
3. How did the evolution of CNS coincide with cephalization

Answer 12

1. Sponges lack nerve cells and symmetry
2. Transmit/process information in form of electrical signals (nerve cells organized into a nerve net in cnidarians and ctenophores)
3. Evolution of head (responsible for feeding, sensing environment, and processing info) are concentrated in CNS

Question 13

Why is basic bilateran body shape known as tube within a tube

Answer 13

Inner tube- gut with a mouth on one end and anus on other (endoderm)
Outer tube- forms nervous system and skin (ectoderm)
Mesoderm- in between muscles and organs

Question 14

Origin of coelum

1. Coelum definition
2. True coelomates
3. Acoelomates
4. Pseudocoelomates
5. Morphological data
6. Molecular data

Answer 14

1. Coelum- an enclosed fluid filled body cavity between tubes (space for O2 and enables internal organisms to move independetly)
2. True coelomates: coelum completely lined with mesoderm
3. Acoelomates- no coelum (no cavity form) such as flatworms
4. Pseudocoelomates- false cavity form (partially lined with mesoderm)
5. Morphological data: predicted gradual evolution
6. Molecular data: predicts coelum arose in ancestral bilaterian

Question 15

Origin of protostomes and deutorosomes

1. Common ancestor?
2. What did ancestor Give rise to?
3. Protostomes
4. Deutorostomes

Answer 15

1. Common ancestor during Cabrian was likely bliterally symmetric triploblast with simple membrane, cephalization, and coelum
2. Ancestor gave rise to radiation of diverse animal linages
3. Protostomes- “first mouth” named for embryonic development of mouth before anus
4. Deuterostomes “second mouth” named for embryonic development of anus before mouth

Question 16

1. How did the 3 germ layers form during gastrulation
   How do they differ in step 3

Answer 16

1. cells move from outside into center of embryo
2. Creates pore outside into center of embryo
3. In deuterostomes: blastopore becomes anus and forms mouth later and in protostomes blastopore may become anus, moth, both, or neither (new view)

Question 17

Segmentation: Modularity

1. What is segmentation?
2. What is a definining characteristic of vertebraes?
3. What monophyletic lineage do vertebrae have
4. What is an invertebrae
5. When did tool kit genes arise?

Answer 17

1. Division of body/body parts into series of similar structures
2. Segmented backbone one of the defining characteristics
3. Monophyletic lineage within the Chordata
4. A paraphyletic group with segmentation conspicuous in annelids and anthropods
5. Arose early in animal evolution and homologous in different phyla

Question 18

Segmentation: Modularity

1. Why are animals segmented differently?
2. What does segmentation enable
3. What is the result of small changes in the expression of “tool kit genes”
4. How does natural selection favor variations

Answer 18

1. Genes subequently lost in some lineages and co-opted in different ways-Convergent evolution of morphological segmentation
2. Segmentation enables specialization
3. Small changes in expression of tool kit genes (like hox genes) can result in novel numbers, shapes, and sizes of body segments
4. Natural selection can favor variations that are adaptive to environments leading to diversification?

Question 19

Feeding

1. What is an animals mode of nutrition
2. How do biologists distinguish what individuals eat
3. How do animals within lineage with similar body plans pursue different foods?

Answer 19

1. Heterotrophs
2. Distinguish what they eat from how they eat
3. Within lineage and similar body plan pursue different food sources if their niche differs. Different lineages with similar niche pursue same food and feeding.

Question 20

WHAT do animals eat

Detrivores
Herbivores
Carnivores
Omnivores

Answer 20

Detrivores- feed on dead organic matter (decaying leaves ie)
Herbivores- Feed on plants or algae (bamboo)
Carnivores- Feed on animals (consume prey)
Ominvores- Combination of plants, animals, fungi, protists, arachae and or bacteria (humans

Question 21

Pariitism

1. Where and what did parasites harvest nutrients
2. Differnence between endoparasites and ectoparisites

Answer 21

1. Harvets nutrients from parts of their host usually much smaller than their victims
2. Endoparasites- lives inside their hosts and have simple, wormline bodies
3. Ectoparasites- live outside their hosts and have limbs or mouthparts that allow them to grasp the hosts

Question 22

Different strategies of eating

1. Suspension feeders
2. Deposit feeders
3. Fluid feeders
4. Mass feeders

Answer 22

1. Suspension- aka Filter feeds capture food by filtering out particles floating in water or air
2. Deposit- Ingest organic material that has been deposited within a substrate or on its surface
3. Fluid- Suck or mop up liquids, like nectar, plant sap, blood, or fruit juice
4. Mass- take chunks of food into their mouths

Question 23

Different strategies of eating

1. Suspension feeders
2. Deposit feeders
3. Fluid feeders
4. Mass feeders

Answer 23

1. Suspension- aka Filter feeds capture food by filtering out particles floating in water or air
2. Deposit- Ingest organic material that has been deposited within a substrate or on its surface
3. Fluid- Suck or mop up liquids, like nectar, plant sap, blood, or fruit juice
4. Mass- take chunks of food into their mouths

Question 24

Sensory Systems and cephalization

1. Key aspects of cephalization
2. What are the common senses of animals

Answer 24

1. Concentration of sensory organs in head regions and great deal of diversity of sensory abilities and structures among the animals
2. Sight, hearing, taste, smell, and touch and most animals have some ability to sense temperature

Question 25

Biliterians
Are cnidarins bilateral/radially smmetric?

Answer 25

Bilaterians are triploblastic, bilaterally symmetric animals
Cnidarians appear radially symmetric but are actually bilaterally symmetric. Some part of genetic tool kit for biliteral symmetry arose before cnidarian and bilateran linages split.