Platyhelminthes & Digestive System

What is bilateral symmetry?

Cut in two equal halves along one plane only

What is radial symmetry?

Cut in two equal halves among all planes

What are the major groups of triploblastic animals?

Protostomes and deuterostomes

What two groups make up protostomes?

Lophotrochozoans and ecdysozoans

Definition of protostomes.

Blastopore develops into mouth first

Definition of deuterostomes.

Blastopore develops into anus first

What are the two structures that make lophotrochozoans unique?

Trochophore: free-swimming larvae; lophophore: feeding structure.

Where do lophotrochozoans live?

Live in water

How do lophotrochozoans move?

Move with cilia or muscle contractions

What are examples of lophotrochozoans?

Platyhelminthes, Mollusca, Annelida

What are the characteristics of ecdysozoans?

Molt exoskeleton as they grow; grow new exoskeleton before they molt old one

What are examples of ecdysozoans?

Arthropods, Nematodes, Tardigrada

What features characterize organisms in phylum Platyhelminthes?

Soft, flattened bodies, acoelomate, blind gut (one opening)

What organisms are Platyhelminthes more complex than?

Cnidarians, sponges

What type of animals are Platyhelminthes?

Simple triploblastic animals

What systems do Platyhelminthes not have?

Circulatory or respiratory system (rely on diffusion)

What system does Platyhelminthes have?

Simple nervous system (anterior cerebral ganglion, nerve cords, eyespots sense light)

Do flatworms (platyhelminths) reproduce sexually, asexually, or both?

Both

How do flatworms reproduce sexually?

Hermaphroditic, do not self-fertilize

How do flatworms reproduce asexually?

Fission, fragmentation, some parasites reproduce asexually inside intermediate host

What is the function of flame cells?

Have flagella that move excess water (and some waste) into tubules for removal; expelled through the mouth

Which group of flatworms is primarily free-living (not parasitic)?

Turbellaria

What are the two examples of trematodes?

Liver flukes and blood flukes (Schistosoma)

What system do tapeworms lack?

Digestive system

Where and how do tapeworms live?

Live in intestines, use scolex to hold on

What forms a tapeworm's body?

Repeating units, proglottids (have male and female reproductive organs, formed continuously).

Definition of autotrophs.

Create their own energy

Definition of heterotrophs.

Must eat other organisms for energy

Definition of herbivores.

Eat plants exclusively

Definition of carnivores.

Eat animals exclusively.

Definition of omnivores.

Eat plants and other animals

Definition of intracellular digestion.

Food taken directly into the cells (protists, sponges)

Definition of extracellular digestion.

Food digested in a cavity before moved into cells (more common in animals).

What is a simple digestive system made of?

One opening to the gut, no specialized regions, food taken directly into cells

What organisms have simple digestive systems?

Cnidarians, platyhelminthes

What is a complex digestive system made of?

Alimentary canal more specialized, food processing can occur in stages, separate mouth and anus.

What happens to ingested food?

Temporarily stored or fragmented physically (chewing, grinding with pebbles)

What happens after physical fragmentation of food?

Chemical digestion: breaking down large food molecules via hydrolysis reactions

What are sugars broke down into?

Polysaccharides to monosaccharides

What are proteins broken down into?

Protein to amino acids

What happens to the smaller subunits of food after chemical digestion?

Absorbed through gut lining into the blood

What happens to food not absorbed by the gut?

Excreted from anus

What is the pathway of food in vertebrates?

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum/cloaca

What is function of the mouth (oral cavity?

Entry, fragmentation, chemical digestion

What is the function of the pharynx and esophagus?

Deliver food to stomach

What is the function of the stomach?

Chemical digestion

What is the function of the small intestine?

Chemical digestion, absorption of nutrients

What is the function of the large intestine?

Absorption of water and minerals

What is the function of the rectum or cloaca?

Expel waste through anus

What are the accessory digestive organs in vertebrates?

Liver, gallbladder, pancreas

What is the function of the liver?

Produces bile (emulsifies fat)

What is the function of the gallbladder?

Stores and concentrates bile

What is the function of the pancrease?

Pancreatic juice, digestive enzymes, and bicarbonate buffer