Bio 204 Exam 3:'(

what are animals

 multicellular eukaryotic heterotrophs that ingest their food

animal cells lack

cell walls

Groups of animal cells are held together by

an extracellular matrix of proteins, the most abundant being collagen

Most animals have tissues

groups of similar cells that function as a unit

most animals use sexual reproduction;

diploid stage dominates the life cycle

Meiosis

is used to form haploid gametes;

fertilization

restores the diploid number by forming a zygote

Zygote undergoes mitosis (cleavage) to form:

a multicellular blastula; 

gastrulation forms

embryonic germ layers

Most animals have larvae

immature forms that are morphologically distinct from the adult

Asymmetry

No definable symmetry

Cannot divide the body into equal halves

EX: sponges

Radial Symmetry

 Top (oral)/ bottom (aboral)

 No left/ right

No back/ front (i.e., no head region)

Any plane divides the animal into equal halves

 Tend to be sessile (don’t move)

EX: sea anemone

Bilateral Symmetry

 Left/ right

Dorsal/ ventral

Anterior/ posterior (i.e., head region; cephalization)

Only one plane divides animal into equal halves; tend to be motile (move around)

EX: crawfish

Diploblastic

two germ layers; radial animals

Triploblastic

three germ layers; bilateral animals

Ectoderm

covers surface of embryo; gives rise to cells in nervous system and those contact with the environment

Endoderm

innermost layer, lining embryonic gut (archenteron); gives rise to lining of the digestive tract

Mesoderm

middle layer in bilaterian animals only; give rise to muscles and most organs (derived from endoderm)

What is a coelom?

fluid-filled cavity lined by a mesodermal peritoneum

Coelomates

possess a true coelom, which functions as a hydrostatic skeleton and isolates organs

Pseudocoelomates

fluid-filled cavity that is not completely lined by mesoderm

Acoelomates

lack fluid-filled cavities of other animals

The presence or absence of a coelom is relevant only  to

triploblastic animals

Protostomes cleavage

spiral & determinate

Protostomes: coelom formation

separate mass

Protostomes: fate of the blastopore (first opening in embryo)

mouth

Deuterostomes cleavage

radial & indeterminate

Deuterostomes coelom formation

fold

Deuterostomes  fate of the blastopore (first opening in embryo)

anus

Who is the sister taxon of animals

Choanoflagellates

Choanoflagellates

Solitary or colonial “protists”

Heterotrophic filter/ suspension feeders – “collar” of microvilli surrounding a flagellum

structured similar to choanocytes (“collar cells”) in sponges and other animals

Possess genes for cellular communication

 What is the significance of the Cambrian Explosion?

Caused big expansion very quickly increased diversity of animals.

Earliest fossils of major living clades

Most are bilaterians (bilaterally symmetrical)

Most have a complete gut (mouth & anus) with a one-way digestive system

Evidence of filter feeding and predation

Aquiferous system

system of canals for pumping water for feeding, respiration, and excretion. pores and canals

Spicules

skeleton 

What does it mean to be monoecious?

Sexually: female and male sex cells within one individual

How do sponges feed?

Choanocytes

sponge anatomy Skeleton is composed of

collagen and spicules provide support and protection

sponge anatomy Spicules may be composed

of calcium carbonate (CaCO₃), silica (Si), or spongin (collagen)

Ostium (pl. ostia)

incurrent opening (little openings)

Osculum (pl. oscula)

excurrent opening (big opening)

Spongocoel

central cavity connecting ostia and oscula

Sponges are multicellular, but they lack:

true tissues

Choanocytes

“collar cells” that circulate water and trap food; resemble choanoflagellates

Amoebocytes

 play roles in digestion and structure

What is cephalization

Formation of a head region

Cnidocytes

 Key innovation for cnidarian success

 Contain toxins for defense and offense

Most common type are nematocysts – sit in capsules and are “sprung”

Oral (mouth) versus aboral (opposite of mouth) ends

Describe the alternation of generations in cnidarians

Egg and sperm 1n

Fertilization 2n

Zygote 2n 

Planula (Larvae) 2n

Developing Polyp 2n 

Mature polyp 2n 

Portion of a colony of polyps  2n 

Feeding polyp 2n

Reproductive polyp and medusa bud

Medusa  

What is coral bleaching?

loss of mutualistic photosynthetic dinoflagellates on account of increased ocean temperatures

Coral reefs

 Provide habitat for thousands of organisms

 Protect coastlines from storms and erosion

 Provide food and medicine

Boost local economies through tourism

why is cephalization beneficial

Indicates direction of movement - head contacts environment first

Special senses are developed– new sensory information is processed by a brain

What is cephalization and why is it beneficial?

Formation of a head region

Allows for free living motile animals

Indicates direction of movement - head contacts environment first

Special senses are developed– new sensory information is processed by a brain

Platyhelminthes Cestoda

edoparasitic tapewokrs (live in animals)

Mollusca Mantle

secretes shell in most species, dorsal layer of skin that secretes shell

Mollusca Radula

 mouth part for feeding, rasping, tongue-like organ (not in bivalves like clams)

Mollusca Foot

adapted for locomotion; varies in shape among different mollusk clades (attached to head)

Mollusca Mantle cavity

contains the respiratory organs (gills)

Mollusca Shell

secreted by mantle; composed of calcium carbonate

Mollusk body plan:

visceral mass

Mollusk Reproductive organs

all mollusks reproduce sexually; most are dioecious

Metamerism

commposed of serial parts

Segments separated by septa

Allows for more precise control of movement

Efficient moverment needs complex nervous and muscular systems

Setae (sing. seta)

bristles for movement)

Bristles made of chitin (hard carbohydrate)

Used for stabilization and movement

In marine species, grow from parapodia (not in earthworms or leeches)

Symbiosis

 Interaction of two different species, in which one or both get benefits

Mutualism

both species benefit

Commensalism

one benefits, other unaffected

Parasitism

one benefits, other is harmed;

endoparasitic

 (inside host)

ectoparasitic

 (outside host)

What is ecdysis?

Covered by a tough exoskeleton called a cuticle that is shed or molted

arthropod Ommatidia

are hexagonal with 6-8 light sensitive cells

 Allow for a wide visual area

arthropod tagmata

body segments (not metamerism)

“Swiss Army Knife” of segments – serve as separate functional units

Two in arachnids, centipedes, and crustaceans (cephalothorax and abdomen); three in insects (head, thorax, and abdomen)

 cons of an open circulatory system

Tissues arent targeted: Less control over blood distribution, requires low metabilisom. Can be vulnerable to infections

 pros of an open circulatory system

 not affected by pressure changes: Allows efficient temperature regulation

clitellum

thickened glandular and non-segmented section of the body wall near the head

How might you distinguish hemichordate “worms” from other worms?

Position of nerve cord

Regular echinoids

 pentaradial symmetry (sea urchin)

Irregular echinoids

secondary bilateral symmetry (sand dollars; heart urchins)

secondary bilateral symmetry (sand dollars; heart urchins)

Hydrostatic pressure for tube feet

Used for locomotion (sometimes feeding)

Madreporite

sieve for water input 

Tube feet found in:

ambulacral grooves

Test

comprising small plates (ossicles) bound together with collagen

Covered by epidermis (skin) with pedicillariae:

pincer-like, surrounded by spines

defense and remove debris from around respiratory structures

What are myomeres?

Obvious segmented muscles

What is the lateral line system?

sense motion

Hox genes

control development of major regions of the vertebrate brain

Origin of jaws

from skeletal support of pharyngeal slits (anterior gill or branchial arches)

Origin of internal fertilization

Claspers - paired appendages

External fertilization Pros:

energetically efficient; potential for lots of offspring

External fertilization cons:

offspring (eggs) unprotected; environmentally constrained

Internal fertilization pros

offspring are protected; parental care; fewer obstacles between sperm and egg

Internal fertilization cons

energetically expensive (for female at least); fewer offspring

Fleshy fin originally an adaptation for swimming, later and

exaptation for walking on land

Limbs with fingers and toes developed from

fleshy lobe fins

Challenges assosiated with the water to land transition of vertebrates Respiration

lungs choanae (internal nostrils) skin (cutaneous respiration)

Challenges assosiated with the water to land transition of vertebrates Support and movement:

 strengthen pectoral and pelvic girdles and limbs

Challenges assosiated with the water to land transition of vertebrates Senses

hearing. Detects airborne sounds vs water motion with lateral line

Challenges assosiated with the water to land transition of vertebrates Origin of tympanic membrane

(ear drum) and columella (stapes)

Challenges assosiated with the water to land transition of vertebrates Water retention/ waste management

concentrate waste products (ammonia in fish; urea and uric acids in tetrapods)

Challenges assosiated with the water to land transition of vertebrates Reproduction

occurs in water for most amphibians (external and internal fertilization)

Challenges assosiated with the water to land transition of vertebrates Metamorphosis aquatic offspring with gills transition to

 adults with lungs

advantages assosiated with the water to land transition of vertebrates

Sunlight

Avoid competition

Find food

Access to atmospheric O2

Escape predators