Chapter 20 - Biodiversity of Invertebrates Flashcards
What is an invertebrate?
Any animal without a backbone.
What is an animal? What are their main characteristics?
Multicellular eukaryotes that are heterotrophic and usually ingest food (through a mouth). No cell walls.
What is the basic animal life-cycle (7 steps)?
- Gametes via meiosis, 2. zygote (2n), 3. zygote divides, 4. blastula stage, 5. gastrula stage, 6. some have a larval stage before metamorphosing into 7. an adult.
What is the blastula stage?
A stage of the animal life cycle when the organism is a hollow ball of cells.
What is the gastrula stage?
A stage of the animal life cycle when the hollow ball of cells from the blastula stage folds in on itself creating the ecto- and endoderm.
What are the three layers of tissues that embryonic animals have? What part of the adult animal do they become?
- Ectoderm - outer layer, becomes skin etc. and nervous tissue.
- Endoderm – inner layer, becomes the digestive tract lining.
- Mesoderm – the middle layer (most, but not all, have this), becomes muscles and most internal organs.
When do we think the lineage to animals occurred? When are the earliest animal fossils from?
1 bya.
Earliest fossils are from 575-550 mya.
When was the Cambrian period? Why was there an explosion of animal life then?
535-525 mya.
Perhaps due to increasingly complex predator-prey relationships, an increase in atmospheric oxygen, or warmer temperatures.
What things do we look at when describing and categorizing animals?
Body symmetry, do they have 2 or 3 tissue layers, what those layers develop into, whether the opening in the gastrula becomes the mouth or the anus, and type of body cavity.
What is a protostome? What is a deuterostome?
Animals where the opening in the gastrula turns into the mouth (protostome) or the anus (deuterostome).
What’s the difference between radial and bilateral symmetry?
Radial: primitive animals with a body plan that radiates from a centre with a top/bottom but no left/right
Bilateral: higher animals with a distinct left and right.
What embryonic tissue layers do all animals have and what’s an additional tissue that most animals have?
More primitive animals only have endoderm and ectoderm.
Most also have mesoderm.
What is coelom?
A fluid filled space between the digestive tract and outer body wall. A body cavity that animals with 3 tissue layers can have.
What is a true coelom?
The coelomic cavity (body cavity) is lined on both sides by mesoderm.
What is a pseudocoelom?
The coelomic cavity (body cavity) is only lined on one side by mesoderm tissue.
What are acoeolomate animals?
Animals with no coelomic cavity (body cavity) at all.
What are Porifera? Where do they rank in the complexity of animals?
The sponges! The simplest, most primitive animals. Not really considered “true” animals or eumetazoans.
What is a sessile animal?
Permanently attached to a surface; not free-moving.
Why are sponges considered primitive?
No true tissues, no real symmetry, no coelom, sessile, more like a colony of protists than a true animal.
What is the structure of a sponge’s body like? How do they feed?
An inner layer of collar cells and amoeboid cells. Collared cells called choanocytes have flagella to make a current in the sponge. Water flows through and out the excurrent pore. All sponges are filter feeders.
What are Cnidarians, their basic characteristics and some examples?
Aquatic invertebrates. Radial symmetry, two tissue layers, sessile (coral or anemones) or free floating (jellyfish). Carnivores with tentacles. Incomplete digestive tract (only a mouth). No body cavity. Cnidocytes (stinging cells) for defence and prey.
What are Platyhelminthes and their basic characteristics?
Flatworms! Bilateral symmetry, three tissue layers, but no coelomic cavity (acoelomates), incomplete digestive tract. Can be free-living or parasitic.
What are Gastrotricha and their basic characteristics?
Gastrotrichs a.k.a. hairybacks. Microscopic animals with 3 tissue layers, bilateral symmetry, a complete digestive tract, and a pseudocoelom.
What are Rotifers and their basic characteristics?
Tiny multicellular organisms. Bilaterally symmetrical, have 3 tissue layers, a complete digestive tract, a pseudocoelom, a hydrostatic skeleton, and organs.