Quaestio: How do other organisms obtain and process nutrients?

Nunc Agenda:

Digestion and Absorption.

Nutrition includes ingestion, digestion and absorption (in that order).

Ingestion: The process of taking-in food.

Digestion: The chemical process in which food molecules are broken down into simpler, smaller forms.

Absorption: The process of transporting nutrients across the cell membrane.

More on Digestion. Many times, digestion is preceded by the

mechanical breakdown of food. Food is cut, crushed, or broken before any chemical

reaction takes place. Mechanical Digestion: The process of

physically breaking down food (increases surface area).

Mechanical breakdown of food increases the surface area of the food particles allows digestion to happen more quickly.

Digestion Happens in Stages.

The chemical breakdown of food occurs in stages. Large molecules are broken into progressively

smaller molecules that can eventually be absorbed. Chemical Digestion: The process of breaking

big molecules into smaller ones.Q: What kind of chemical process do you think this is?

A: Hydrolysis! Hydrolysis is the chemical breakdown of bonds (through the addition of water). Hydrolytic enzymes are involved.

Intracellular Vs. Extracellular Digestion

Intracellular Digestion: takes place within the cell environment. Single-celled organisms perform intracellular

digestion on food vacuoles by using lysosomes.

Extracellular Digestion: takes place outside the cell environment. Many multicellular organisms carry out extracellular

digestion. Humans do as food passes through the gastrointestinal system. (i.e. mouth, stomach, small intestine). They then carry out intracellular digestion once food molecules enter cells.

Digestion in Protists.

Protists have intracellular digestion. (unicellular, eukaryotic organisms)

2 example organisms (protozoans): 1. Amoebas 2. Paramecia

The Ameba.

Amebas have pseudopods, or “false feet,” that are used for locomotion and digestion. These projections of the cell move and shift by

filling with cytoplasm. they engulf food particles through phagocytosis. The particle is enclosed in a food vacuole Lysosomes fuse with the vacuole and digestive

enzymes break down the food.

                                                                                                                                                                                                     

Digestion taking place: note number of food vacuoles.

Amoeba proteus engulfing cells of Paramecium sp. by phagocytosis. LM. [Robert Brons/BPS]

Paramecium Digestion. Cilia: Tiny hairlike organelles at the surface of

the cell. Ciliates (I.e. paramecia) are the most complex

protozoans. Their form of locomotion is considered more evolved than that of the flagellates or amoeboids.

Uses of cilia: Locomotion Nutrition

The cilia sweep food particles down the oral groove into the organism’s gullet.

More on Paramecium Digestion. When food collects at the end of the

paramecium’s gullet, the cell membrane bulges inward and pinches off, forming a food vacuole.

As with the amoeba, a lysosome fuses with the food vacuole. Digestion occurs within the food vacuole when the lysosome’s enzymes enter it.

Indigestible material leaves the paramecium through the anal pore.

Paramecium Movies

See Web Movies.

Watch Paramecium Locomotion Watch Paramecium Up-Close (Cyclosis

and Oral Groove Cilia Action)

http://www.microscopyu.com/moviegallery/pondscum/paramecium/

The Hydra. Hydras are coelenterates in the animal kingdom.

(Phylum = Cnidaria). Hydras are about five millimeters long and live in fresh water. They are in the same phylum as jellyfish and coral.

Hydras normally attach themselves to underwater objects.

Hydras have a tubelike body with only one opening: a mouth. The mouth leads to an internal cavity.

The jellyfish Medusa (Phylum: Cnidaria, Class: Scyphozoa)captures a shrimp (Phylum: Arthropoda, Subphylum: Crustacea).

Jellyfish are relatives of hydra.

The Real Medusa

The Hydra

Hydras are only two cell layers thick. Outer Layer:

Ectoderm. Inner Layer:

Endoderm. Forms a

gastrovascular cavity

The hydra’s namesake.

The green hydras we saw in our pond lab have a symbiotic relationship with algae. The algae receive protection within the body of the hydra while the hydra receives a food supply (Algae are phototrophs). Algae contain the photosynthetic pigment chlorophyll.

Chlorohydra viridissima

Hydra in Action.

See Web Movies.

http://www.microscopyu.com/moviegallery/pondscum/hydra/

Digestion in Hydra. The tentacles bring food to the mouth

Digestion is intracellular and extracellular. Endoderm cells secrete enzymes into the

gastrovascular cavity(Extracellular digestion) when dissolved, endoderm cells engulf food and

intracellular digestion takes place Once broken down, food molecules diffuse quickly

across the cell layers of the hydra.

Key Idea: The Hydra has a two-way digestive tract. The mouth is both an entrance for food and an exit for wastes

Question

Compare digestion in the amoeba and paramecium

How is digestion in the hydra similar to protozoans?

The Earthworm.

Classification: phylum Annelida (the segmented worms) in the Animal kingdom.

The earthworm, like the hydra, is multicellular.

Its body system is more complex than that of the hydra.

Nutrition in the Earthworm.

Earthworm anatomy: The earthworm consists of a “tube-within-a-

tube” body design. Outer tube: body wall. Inner tube: digestive system (aka the alimentary

canal).

Digestion in the Earthworm.

one-way digestive path. Food enters through the mouth, proceeds

through the body, and leaves through the anus.

Food is broken down mechanically and chemically in the earthworm.

Advantages to One-Way Digestion.

Can you think of some advantages the earthworm’s form of digestion has over the hydra’s form of digestion?

Advantages. The earthworm doesn’t have outgoing

waste passing through the same opening as its incoming food.

The earthworm can still eat while digestion is taking place. The hydra can only ingest food after digestion is completed.

Allows for specialization of different parts of the digestive system.

What Does an Earthworm Eat?

An earthworm eats large quantities of soil, as well as leaf litter and other decaying plant matter.

Earthworms process the soil, obtaining nutrients from organic matter with it. [Richard Humbert/BPS]

The Details.

Earthworm Digestive Anatomy. Mouth: Where food enters. Pharynx: Pulls food into the mouth with a

sucking action. Esophagus: pushes the food through to the

rest of the digestive tract through peristalsis. Crop: temporarily stores food and gradually

releases it into the gizzard. Gizzard: A thick-walled grinding organ that

crushes food (mechanical breakdown).

More Details.

Earthworm Digestive Anatomy. Intestine: site of chemical digestion and

absorption of nutrients Typhlosole: A fold in the intestinal wall that

increases the surface area for more absorption to take place.

Anus: Where the undigested materials are egested and the digested wastes are excreted.

Earthworm Digestion Animation.

See Web Animation.

http://www.tvdsb.on.ca/westmin/science/snc2g1/wormdig.htm

The Grasshopper.

Grasshoppers are arthropods (kingdom Animalia, phylum Arthropoda). They are in the Insecta class.

What else is in the Arthropod phylum?

Arthropods are identified by their hard exoskeleton (made of chitin!).

Nutrition in the Grasshopper. Digestive Anatomy of the Grasshopper Similar to the earthworm, with the addition of:

Mouthparts (jaws): Adapted for chewing Salivary Glands: Add saliva to food enzymes break

down food. Rectum: Water is absorbed here.

Broad-winged katydid, a herbivore, feeding. [Peter J. Bryant/BPS]

How is earthworm digestion similar to grasshopper digestion? How are they different?

Compare and contrast digestion in unicellular and multicellular organisms.