Invertebrate Animals – Lecture Review

These 40 question-and-answer flashcards cover key definitions, phylum characteristics, life-cycle concepts, and notable examples from the invertebrate lecture notes.

What four cellular-level traits are shared by all animals?

They are eukaryotic, multicellular, heterotrophic, and adults are diploid while their gametes are haploid.

What is the most common mode of reproduction in animals?

Mostly sexual reproduction.

Approximately how many animal phyla are recognized?

About 35 phyla.

Which modern protists are considered the closest living relatives of sponges?

Protistan choanoflagellates.

In animal phylogeny, what distinguishes organisms that have 'no true tissues' from those with 'true tissues'?

Organisms without true tissues (e.g., Porifera) lack organized tissue layers, whereas organisms with true tissues possess differentiated tissue layers (e.g., Cnidaria and all bilaterians).

Which two major symmetry patterns occur in animals and how are they defined?

Radial symmetry—body parts arranged around a central axis; Bilateral symmetry—left and right sides are mirror images with distinct head and tail.

Define a protostome in embryological terms.

In protostomes, the first opening (blastopore) of the embryo becomes the mouth.

Define a deuterostome in embryological terms.

In deuterostomes, the first opening (blastopore) of the embryo becomes the anus.

What is an incomplete digestive system?

A digestive system in which food enters and wastes exit through the same opening (gastrovascular cavity).

What is a complete digestive system?

A digestive system with two separate openings—one for ingestion (mouth) and one for egestion (anus).

List the three primary germ layers found in a triploblastic animal.

Ectoderm, mesoderm, and endoderm.

Place these early embryonic stages in order: blastula, zygote, gastrula.

Zygote → Blastula → Gastrula.

What is metamorphosis in the animal life cycle?

A developmental transformation that changes a larval form into an adult form.

Which invertebrate phylum exhibits asymmetry?

Phylum Porifera (sponges).

Which two phyla include animals that are radially symmetrical as adults?

Cnidaria and adult Echinodermata.

Why are echinoderms considered an exception to the usual symmetry rule?

Their larvae are bilaterally symmetrical, but adults are radially symmetrical.

Do sponges (Porifera) possess organ systems?

No, they lack true organs and organ systems.

How many tissue layers are present in Cnidarian embryos?

Two (diploblastic).

Do Platyhelminthes have a complete or incomplete digestive system?

Incomplete.

Name two phyla that exhibit body segmentation.

Annelida and Arthropoda.

What type of symmetry do adult arthropods possess?

Bilateral symmetry.

Name the three major Sponge cell types and their primary roles.

Choanocytes—create water currents and capture food; Amoebocytes—digest, transport nutrients, and aid in skeleton formation; Pinacocytes—form the protective outer layer.

What is a cnidocyte?

A stinging cell unique to Cnidarians used for prey capture and defense.

What are the two body forms seen in Cnidarians and give an example of each.

Polyp (e.g., sea anemone) and Medusa (e.g., jellyfish).

List the free-living and parasitic classes of flatworms.

Free-living: Turbellaria (planarians); Parasitic: Trematoda (flukes) and Cestoda (tapeworms).

Why are flatworms dorsoventrally flattened?

To maximize surface area for diffusion of gases and nutrients because they lack circulatory and respiratory systems.

Give one example of a freshwater flatworm.

Planaria.

Name the three major Molluscan classes with one example each.

Gastropoda—snail; Bivalvia—clam; Cephalopoda—octopus.

Provide one terrestrial and one aquatic example of molluscs.

Terrestrial: land snail; Aquatic: octopus.

In a typical gastropod, what structure is used for scraping food?

The radula.

Why are earthworms beneficial to soil ecosystems?

They aerate soil, decompose organic matter, and add nutrient-rich castings.

Name the three classes of annelids and an example of each.

Polychaeta—bristle worms; Oligochaeta—earthworms; Hirudinea—leeches.

Describe the movement of nematodes.

Thrashing, whip-like motion using only longitudinal muscles.

Give a medically significant example of a nematode.

Ascaris.

List the four main groups of arthropods.

Insects, Arachnids, Crustaceans, and Myriapods.

Which arthropod group contains the greatest number of species?

Insects.

Provide one aquatic and one terrestrial example of arthropods.

Aquatic: crab; Terrestrial: ant (or spider/grasshopper).

Differentiate between complete and incomplete metamorphosis in insects.

Complete: egg → larva → pupa → adult; Incomplete: egg → nymph → adult.

What is the water vascular system in echinoderms and its primary function?

A network of fluid-filled canals used for locomotion, feeding, gas exchange, and excretion.