Lab 1 (Protozoa, Porifera, Cnidaria) Flashcards
Why are these groups considered the more “primitive” animals?
- They are single-celled organisms (protozoans)
- They are multi-cellular animals (metazoan)
- They either have a cellular-level organization or a tissue-level organization
Which group is the single-celled animals?
Protozoan
What characteristics do protozoans share?
- There is no cell wall (this is found only in plant cells) but there is a cell membrane
- Organelles are present, but no tissues or organs
- Cytoskeleton, a network of protein fibres, is present
- Live in water and/or moist soil
What are the three different groups of protozoans?
Amoeba
Paramecium
Trypanosoma
Explain the basics of the Amoeba
- They live in fresh and salt water and in moist soil
- They are bottom-dwellers that require a surface on which they glide
- They feed on microscopic organisms (algae, bacteria, other protozoa)
- Come in many shapes
What is the support in the Amoebas?
- Outer cell membrane provides structure by enclosing and containing the cell contents, and acts as a semi-permeable environmental barrier through which water, nutrients and other products can flow
- Beneath the cell membrane is a thin, clear layer of stiffened ectoplasm
- Inner material is fluid endoplasm
What is ectoplasm strengthened by (in Amoebas)?
By a meshwork of fibrous actin (a protein found in muscles of other organisms)
Where do you find the organelles (in Amoebas)?
In the inner material
What does the endoplasm contain (in Amoebas)?
A network of protein fibres called the cytoskeleton
What is the movement in Amoebas?
- They use extensions of their membranes called pseudopodia to move and change shape
- Endoplasm flows into the leading tip of the pseudopod, where it is converted into stiffened ectoplasm
- Ectoplasm at the “tail end” of the amoeba converts to streaming endoplasm to replenish the forward flow
What is the pseudopod used for in Amoeba movement?
To grasp a surface and pulls the rest of the cell forward
What is the feeding/digestion of the Amoebas?
- They feed using a process called phagocytosis
- Waste products and excess water are removed through the cell membrane
What is phagocytosis?
Where they encircle food items with pseudopodia, forming water-filled food vacuoles that are later digested by enzymes
What is reproduction in Amoebas?
- One of the largest organelles is the nucleus (which carries genetic material)
- They produce via asexual reproduction
What is binary fission in the Amoebas?
They make a copy of their DNA, then create two new nuclei and splits into two new cells
Explain the basics of the Paramecium
- They are active ciliate protozoans found in freshwater that contain a lot of organic matter
- They are “slipper-shaped”
- They feed on small particles like bacteria
What is the support in the Paramecium?
- They have a thin, clear outer ectoplasm lying beneath the cell membrane
- They have an inner endoplasm containing organelles and the cytoskeleton
What is the movement of the Paramecium?
- The entire outer surface of the organism is covered with hair-like cilia
- The oar-stroke action of the cilia moves the animal forward or in circles
What is the feeding/digestion of the Paramecium?
- The oral groove is lined with cilia that draw food particles into the endoplasm (where food vacuoles are formed for later digestion)
- Waste products and excess water are removed through the cell membrane
- Large, round, contractile vacuoles are responsible for maintaining osmotic balance
What is osmotic balance?
pumping excess water out when needed
What is the reproduction of the Paramecium?
- They have nucleus (micronucleus) and one or more micronuclei
- Can reproduce asexually (binary fission) or sexually (conjugation)
What is conjugation?
Where DNA is swapped with another individual
Explain the basics of the Trypanosoma
- They are a parasite that can cause serious illness (sleeping sickness, Chagas’ disease)
- They usually need an intermediate blood-sucking insect host in order to infect their human host
What is the support of the Trypanosoma?
- The same structures are present in Amoebas and Paramecium
What is the movement of the Trypanosoma?
- They have a whip-like organelle at one end called a flagellum (which moves the organism through its fluid environment)
What is the feeding/digestion of the Trypanosoma?
- They absorb their food from its hosts’ blood or other blood or other body fluids directly through its cell membrane
What is the reproduction of the Trypanosoma?
- Both the large nucleus and the kinetoplast contain DNA
- Reproduce via binary fission and sexual reproduction
Explain the basics to the Phylum Porifera
- Sponges
- They are multi-cellular organisms
- They have no tissues or organs
- They are a collection of different kinds of cells that carry out specific tasks in an organized way
- They have cellular-level organization
- Adult sponges are sessile
- Adult sponges may be colonial or solitary
What are some characteristics shared by Poriferans?
- Pore and canal system
- Choanocytes
- Spicules
- Spongocoel and osculum
What is the support of the sponges?
- The body wall is reinforced with rigid, pointy, crystalline calcium carbonate structures called spicules
- Other poriferans lack spicules (they rely on spongin for structural rigidity
What are spicules?
They act as a skeleton, providing support
What is the feeding/digestion of the sponges?
- The body wall comprises a system of canals and pores
- Finger-like projections point outward along the length of the body wall (these are radial canals)
- Radial canals open into the body cavity, called the spongocoel, via small openings (apopyles)
- Between adjacent radial canals called incurrent canals
- Water (containing food particles and oxygen) first enter the incurrent canals
- Then it passes through tiny openings (prosopyles) into the radial canals, moves through the apopyles, then into the spongocoel and finally out through the osculum, removing waste products
- This process of water movement is facilitated by the action of choanocytes
What are choanocytes?
- Specialized flagellated cells that line the radial canals
- The whip-like action of the flagella draws water in from the incurrent canals, trapping food particles and oxygen as water flows past
What are the classes of the Phylum Cnidaria?
Hydrozoa
Scyphozoa
Anthozoa
Explain the basics to the Phylum Cnidaria
- Among the most primitive true multi-cellular organisms
- Tissue level organization (lack true organs)
- They all share a unique feature (stinging cells called cnidocytes)
- They all are radially symmetrical
- Two types of body forms (sessile polyp and free-swimming medusa)
- Some display both forms while others only display one
Explain the basics of the Class Hydrozoa
- Small, solitary cnidarian
- Only exists in the polyp form
- Found in pools, streams and ponds (usually on the underside of aquatic vegetation)
What is the support of the Class Hydrozoa?
- The outer layers of tissue of the animal make up the epidermis or skin
- This animal relies on internal water pressure to maintain its form
What is the movement of the Class Hydrozoa?
- Are sessile and attach to a surface using a sticky substance extruded from glands in the basal disk
- They can move their body parts, including tentacles via a simple network of nerves that control muscle fibres
What is the feeding/digestion of the Class Hydrozoa?
- The circle of long tentacles at the other end should be evident, the mouth lies at their base
- They can move, retract and extend their tentacles in response to environmental stimuli and are used in feeding
- Tentacles are lined with groups of cnidocytes, each of which encloses a stinging organelle called a nematocyst
- Food passed from the mouth into the gastrovascular cavity (where digestive enzymes partially digest the food)
- Cells lining the cavity engulf what remains, and complete the digestion cellularly
- Their digestion is a two-way street: there is no anus, so any waste/scraps are ejected from the mouth
What are nematocysts?
- Tiny capsules containing a coiled, threadlike stinging filament
- Some are small, and are used simply to hold or entangle prey
- Some are large, hollow and equipped with nasty barbs that embed in the prey item before they inject a paralyzing toxin
- Helpless prey can then be safely dragged towards the mouth to be ingested
What seems to trigger the firing of the nematocyst filament?
Disturbing the hair-like cnidocil on the outer edge of the cnidocyte
What is the reproduction of the Class Hydrozoa?
- Can use budding to reproduce asexually
- A new animal, complete with tentacles and mouth, forms from the epidermis, then eventually breaks off from the parent
- Can also reproduce sexually; some species posses both ovaries and testes (monoecious), while others are dioecious and have only one of the two
Explain the basics of the Class Scyphozoa
- True jellyfish
- Made up of 94-99% of water
- Their body parts are arranged in multiples of four so they are said to have tetramerous radial symmetry
- Both polyp and medusa form
- The medusa form are active swimmers
- Both forms posses stinging cnidocytes
What is the support of the moon jellyfish?
- They parasol-shaped surface is called the bell
- Hydrostatic skeleton allows it to maintain its shape
- The outer margin is divided into sections; at each junction there is a bundle of sensory structures called rhopalia
What is a rhopalia?
Consists of a statocyst and an ocellus (used for balance/orientation and light perception, respectively)
What is the movement of the moon jellyfish?
- A simple, decentralized nervous system controls muscle fibres that move the animals bell and allow it to swim in the water column
- The same system controls the tentacles
What is the feeding/digestion of the moon jellyfish?
- Along the margin are many small tentacles; these should not be confused with the four large oral arms
- The tentacles are used to filter tiny prey towards mucous on the margin; prey are collected by the trough-shaped oral arms which direct food to the mouth
- The mouth opens into a short gullet, which leads to the stomach
- Four gastric pushes extend from the stomach
- These structures can be indistinct by themselves, but they also contain the gonads, which are horseshoe shaped and clearly visible
- Near the pushes are thin gastric filaments, which are lined with cnidocytes; these subdue uncooperative prey before digestion takes place in the gastrovascular cavity
What is the reproduction of the moon jellyfish?
- They are dioecious and fertilization takes place externally, after the gonads shed sperms or eggs from the gastric pouches; these are discharged through the mouth
- Young embryos develop in the folds of the oral arms, until, as ciliated larvae, they escape the parent and attach to a substrate.
- There, the larva develops into a tiny sessile polyp called a scyphistoma
- The scyphistoma becomes a multi-tiered strobing, form which tiny medusae called ephyra bud off
- The ephyra mature to become adult jellyfish
Explain the basics of the Class Anthozoa
- Sea anemone
- Marine animal that can live comfortably in intertidal zones as well as depths of up to 75m
- Only the polyp form
What is the support of the sea anemone?
- The body has 3 main regions
1) Oral disc (tentacles and mouth are located)
2) Cylindrical column (forms the main body of the animal)
3) Basal disc (the animal attaches itself to a substrate using sticky glandular secretions) - Hydrostatic skeleton
What is the movement of the sea anemone?
- Strong muscles running the length of the column allows the anemone to retract or extend on response to stimuli
- Muscles also control the tentacles
- Although the anemone is sessile, it can glide very slowly on the basal disc
What is the feeding/digestion of the sea anemone?
- Tentacles, armed with cnidocytes, capture prey
- Food is then drawn into the mouth, where it then passes through the pharynx and into the gastrovascular cavity, where digestion takes place
- Waste goes back out the mouth
What is the reproduction of the sea anemone?
- Gonads resembling thin stacks of small coins are visible on either side of the pharynx
- Sex cells are released from these and pass through the mouth
- Fertilization is external
- Fertilized eggs hatch tiny larvae that settle to the substrate and turn into single polyps
