Chapter 30- Introduction to Animals, Sponges and Cnidarians

Characteristics of Animals

• Multicellular

• No cell walls

• 600 million to 1.5 billion years old

• Monophyletic

What is extracellular matrix?

allows animals to stick together and communicate

How do animals obtain nutrient?

Through ingestion

Are animals heterotrophic or autotrophic?

Heterotrophic- consume other organisms for carbon and energy

How do fungi and plants obtain nutrition?

Fungi absorb; Plants photosynthesize

Do all animals have tissue?

Yes, most animals do except sponges do not

Do animals reproduce sexually or asexually?

Most sexually, some asexually

Which stage is dominant in animals: haploid or diploid?

Diploid (2N)

What are the only haploid (1N) cells in animals?

Gametes

What protist do animals share a common ancestor with?

Choanoflagellates

Characteristics of choanoflagellates

• They are single celled or colonial

• live in salt and fresh water

• protist

What is cleavage?

Embryonic cell division, the ball stay’s the same size but the cells get tinier

What is the sequence of embryonic stages?

Zygote → cleavage → blastula → gastrula

What is gastrulation?

Rearrangement of the embryo; formation of 3 germ layers.

What does the ectoderm form?

Outer covering and nervous tissue.

What does the endoderm form?

Lining and organs of digestive tract.

Characteristics of diploblasts?

• Radial symmetry

• Neural net (nervous system)

• Only Cnidaria’s

• No coelom

• 2 germ layers (ectoderm, endoderm)

What forms from the mesoderm?

Circulatory system, muscles, some organs.

Characteristic of triploblasts

• Bilateral symmetry

• Central nervous system (CNS)

• Coelom development

• 3 germ layers (ectoderm, mesoderm, endoderm)

What is a coelom?

A fluid-filled space separating the outer body from the digestive tract, lined with mesoderm

Functions of a coelom?

• Cushions organs

• absorbs shock

• acts like a skeleton

• allows organ movement

• provides space

Acoelomate phylum and characteristic?

platyhelminths (flatworms); no body cavity.

Pseudocoelomate phylum and characteristic?

• Nematoda (roundworms)

• cavity partially lined with mesoderm (one side only)

Coelomate phyla and characteristic?

• Annelida

• Mollusca

• Arthropoda

• cavity fully lined with mesoderm (both sides).

What does “A” stand for in coelom terms?

Absent (no cavity)

What does “Pseudo” stand for?

Partial (1 mesoderm side only)

What defines a “true” coelom?

Totally surrounded by mesoderm

Characteristic of protostomes?

• Blastospore becomes the mouth

• spiral and determinate cleavage

• Ex: Mollusks, Annelids, Arthropods

Characteristics of deuterostomes?

• blastospore becomes the anus

• radial and indeterminate cleavage

• Ex: echinoderms, chordates (including humans)

Lophotrochozoans Characteristics

• They don’t molt

• Lophophore (feeding)

• trochophore (larval stage)

• Ex: Mollusca, Annelida

Ecdysozoans Characteristics

• They molt

• Have a tough outer layer (exoskeleton)

• Ex: Arthropoda, Nematoda

Deuterostomes Characteristics

• Don’t molt

• Anus forms first

• flexible development (can form twins)

• Ex: Echinodermata, Chordata, Humans

Key difference between the three clades?

• Lophotrochozoans grow without molting

• Ecdysozoans molt

• Deuterostomes: anus forms first, no molting.

How many times has segmentation evolved?

At least 3 times (homoplasy)

Advantage of segmentation?

Allows for specialization.

What percent of named animal diversity are "cute" animals?

Less than 0.5%.

What are key features of sponges (Porifera)?

• No germ layers

• no tissues (parazoa)

• asymmetrical

• no body cavity

• filter feeders

• sessile adults

• swimming larvae with cilia

• mostly marine

• hermaphroditic reproduction with internal fertilization

What are the three components of sponge body walls?

• Outer epithelial cells

• middle mesophyll with amoebocytes

• inner choanocytes (specialized cell)

How many cnidarian species are there?

10,000

Where do most cnidarian species live?

Marine environments

Characteristics of cnidarians

• Diploblastic

• eumetazoans (true tissue)

• Radial symmetry

• Gastrovascular cavity (incomplete)- digestive system

• No coelom

What is a cnidocyte?

Specialized stinging cell.

What is a nematocyst?

Organelle that contains an injectable thread.

What is the structure of corals and their ecological importance?

• Corals are cnidarian polyps with calcium carbonate skeletons

• have symbiotic dinoflagellates (protist)

• are ecosystem engineers supporting 500 million people

What causes Reef damage?

• Reef damage is caused by coral bleaching from increased temperatures which kicks dinoflagellates out of coral animal.

Is the Jellyfish Apocalypse a real concern?

No, jellyfish populations fluctuate naturally, and the phenomenon is overstated.