Cnidarians

What are the 4 key features of Cnidarians?

Radial symmetry

Soft bodied animals with stinging tencatacles around mouth

Solitary/colonial

Speciaized cells and tissues

Epidermis

Outer layer of cells that covers the Cnidarians body

Mesoglea

Space inebtween gastrodermis and epidermis; may contain wandering amebocytes. Thin in polyps, thick in medusa

Explain photosynthetic symbiosis in Cnidarians.

Some Cnidarians host many species of protists. This species of protists are photosynthetic, meaning they perform photsynthesis in order to make their own food. This food is also for the Cnidarian, which provides protection to these protists, therefore making a symbiotic relationship.

What is a caveat of photsynthetic symbiosis?

Cnidarians which have this relationships can only survive in sunlit, shallow waters that are nutrient poor (Coral reefs).

Where is the nerve net located in Cnidarians?

Around the mouth

Explain the function of the two sensory cells.

Ocelli are eyespots which detect light. Statocysts ensure that the animal is able to balance

Where are the sesnory organs located?

around the bell of the Cnidarian.

Explain how the medusa form moves.

When stimualted by the nervous system, the epidermal cells will contract, causing a jet propulsion force, moving the Cnidarian forwards.

How do medusae do respiration, exretion, and transport without an internal transport system?

They use diffusion to exchange gases and get rid of waste through their body walls, the pores as they live in clean constantly flowing water. To excrete, they simply put back the indgiested food through the mouth/anus.

How do the polyps in Cnidarian reproduce? What method?

Aseual reproduction. Budding

How does budding work

A bud grows on a polyp. This bud will fall off and grow into a new polyp.

How does the medusa form of polyps reproduce?

Sexual reproduction. The medusae will release a gamete, fertilization will occur, and then this will turn into a ciliated (swimming) larva. The larva will settle, then become a polyp.

Examples of Hydrozoa

Portuguese man of war, Hydra

Schyphozoa

“True” jellyfish

Anthozoa examples

Coral, Sea anemone

What does the life cycle of a Hydrozoa consist of?

A primary polyp stage, and a short medusa stage

How do hydrozoan polyps grow?

in branching, sessile colonies

Size of hydrozoan colonies

few cm-1m

How do feeding, reproduction, and defense occur?

Through specialized polyps in the colonies

How does reproduction in hydrozoan polyps occur?

A specialized reproductive polym will bud off tiny medusae, which produce egg and sperm

What is distinct about Hydras, setting them apart from other species in Hydrozoa?

They live as solitary polylp (not colonial), lack the medusae stage, live in freshwater, and are motile

How do Hydras move?

By somersaulting

How do HYDRAS reproduce?

Sexually, by prodcuing sperm and eggs through their body walls, or asexually, through budding.

Why are some Hydras hermaphrodites?

Because they have both reproductive organs, producing both sperm and egg

Is the portuguese man of war a single organism? Why/Why not?

Not, it is a colonial polylp. It contains many specialized polylps working together.

How does the portuguese man of war float?

It has a gas filled poylp.

How long can portugues man of war’s grow until

30 cm long

Name the 4 specialized poylps found in the portuguese man of war.

Float poylp, feeding poylp, reproductive poylp, and tentacle poylp (stinging)

What are nematocysts?

They are a specilized type of cell found on Cnidarian tentacles. They contain a poison loaded dart which fires when triggered by touch.

What are the effects of the nematocysts of the portuguese man of war?

intense burning, swelling, and allergic reactions

What does the life cycle of the class Scyphozoa consist of?

A dominant medusa stage which is large, free swimming, and long living, with a short poylp stage that is limited to the tiny larva

What are the dimensiosn of the largest recorded jellyfish?

3.6 m in diameter, tentacles are upto 30 m long

What does the life cycle of the class Anthozoa consist of?

It only consists of a polyp stage.

How does sexual and asexual reproduction in Anthozoa occur?

In sexual repdouction, the poylp releases gametes into the water, and upon fertilization, a ciliated larva will form from the egg, and settle to make a new poylp. Asexual reproduction=budding.

What is the main characteristic of Sea anemones? how do they feed

They are solitary marine poylps found in low tide zones to the deep sea. They feed using their tentacles and nematocysts.

What do sea anemones species lviing in shallow waters rely on?

photosynthetic symbionts, which provide energy

What are key characteristics of corals?

They are mostly colonial polylps, they resemble tiny sea anemones, and produce a harde calcium carbonate exoskeleton (limestone)

How do corals reproduce?

Asexual reproduction, budding

What is one major role of coral reefs in the ocean ecosystem?

They provide habitat for thousands of marine species.

What are some key facts about the Great Barrier Reef?

It is over 2000 km long, wider than 80 km in some areas, and has more mass than the largest human cities.

How does coral bleaching occur?

When corals expel their symbiotic algae, zooxanthellae.

Where do the symbiotic algae, zooxanthellae, found in coral live, and what do they provide?

Inside coral tissues and provide photosynthesis.

What triggers the expulsion of zooxanthellae in corals?

Environmental stressors such as rising ocena temperatures, pollution, UV radiation, and ocean acidification

What is ocean acidification?

Ocean acidifcation occurs dues to the excess amount of CO2 in the earths atmosphere, which is absorbed by the ocean. This forms carbonic acid, which lowers the ocean’s pH level.

How does coral bleaching occur?

Through the expulsion of photsynthetic symbionts - they give algae their colour.

What are the impacts of coral bleaching?

Corals lose their main energy source, and may starve and die.

What are some ways we can protect our coral reefs?

Through reducing carbon emissions, cutting down on pollutions, practicing ocean friendly choices.

What is an example of a symbiotic relationship in coral reef ecosystems?

Clownfish and sea anemones.

How are coral reefs important to humans?

They provide food, materials (like shells and pearls), coastal protection, and support tourism and cultural value.

How could corals and sea anemones be useful in medicine?

They produce bioactive chemicals, which have the potential to be anti-cancer drugs

Why are nematocyts important to scientists?

They help them study nerve function.