Ch 27 Animal Diversity, Ch 28 Invertebrates, Ch 29 Vertebrates, Ch 45 Population and Community Ecology

Animal

Multicellular, eukaryotic, heterotrophic organism that ingests food.

Metazoa

Group containing all animals.

Common characteristics of animals

Multicellular, eukaryotic, heterotrophic, lack cell walls, develop from embryos, possess specialized tissues (most animals).

Heterotroph

Organism that obtains nutrients by consuming other organisms.

Body plan

The overall morphology and organization of an animal.

Hox genes

Master control genes that regulate body plan development during embryogenesis.

Importance of Hox genes

Control the development and placement of body structures.

Embryogenesis

The process of embryo development.

Cleavage

Rapid mitotic divisions of the zygote after fertilization.

Blastula

Hollow ball of cells formed during early embryonic development.

Gastrulation

Process that forms the embryonic germ layers.

Gastrula

Embryonic stage following gastrulation.

Organogenesis

Formation of organs during embryonic development.

Germ layer

Layer of embryonic cells that develops into specific tissues and organs.

Ectoderm

Outer germ layer that forms skin and the nervous system.

Mesoderm

Middle germ layer that forms muscles, skeleton, blood, kidneys, and connective tissues.

Endoderm

Inner germ layer that forms the digestive tract, liver, pancreas, and respiratory lining.

Parazoa

Animals lacking true tissues.

Example of Parazoa

Sponges (Porifera).

Eumetazoa

Animals with true differentiated tissues.

Examples of Eumetazoa

Cnidarians, ctenophores, echinoderms, arthropods, chordates, and most other animals.

Specialized animal tissues

Nervous, muscle, connective, and epithelial tissues.

Types of body symmetry

Asymmetry, radial symmetry, and bilateral symmetry.

Asymmetry

No plane divides the body into equal halves.

Example of asymmetrical animal

Sponge.

Radial symmetry

Body parts arranged around a central axis.

Examples of radial symmetry

Jellyfish, sea anemones, adult cnidarians.

Bilateral symmetry

Only one plane divides the body into left and right halves.

Examples of bilateral symmetry

Insects, worms, humans, fish, birds, mammals.

Secondary radial symmetry

Radial symmetry that evolved from bilaterally symmetrical ancestors.

Example of secondary radial symmetry

Echinoderms.

Cephalization

Concentration of sensory organs and nervous tissue at the anterior end.

Which animals exhibit cephalization?

Most bilaterally symmetrical animals.

Diploblast

Animal with two germ layers.

Germ layers in diploblasts

Ectoderm and endoderm.

Examples of diploblasts

Cnidarians and ctenophores.

Triploblast

Animal with three germ layers.

Germ layers in triploblasts

Ectoderm, mesoderm, and endoderm.

Advantages of the mesoderm

Allows development of muscles, organs, circulatory systems, and greater complexity.

Coelom

Fluid-filled body cavity completely lined with mesoderm.

Functions of a coelom

Protects organs, allows organ growth, cushions organs, and improves movement.

Acoelomate

Animal lacking a body cavity.

Example of an acoelomate

Flatworm (Platyhelminthes).

Pseudocoelomate

Animal with a body cavity partially lined by mesoderm.

Example of a pseudocoelomate

Roundworm (Nematoda).

Eucoelomate

Animal with a true coelom completely lined by mesoderm.

Examples of eucoelomates

Annelids, mollusks, arthropods, echinoderms, chordates.

Advantages of a true coelom

Supports larger organs, efficient circulation, shock absorption, and greater flexibility.

Blastopore

Opening that forms during gastrulation.

Protostome

Animal whose mouth develops from the blastopore.

Examples of protostomes

Arthropods, mollusks, annelids.

Deuterostome

Animal whose anus develops from the blastopore.

Examples of deuterostomes

Echinoderms and chordates.

Spiral cleavage

Cleavage pattern in most protostomes where cells are offset.

Radial cleavage

Cleavage pattern in deuterostomes where cells align directly above one another.

Determinate cleavage

Cleavage in which cell fate is fixed early in development.

Which animals undergo determinate cleavage?

Protostomes.

Indeterminate cleavage

Cleavage in which embryonic cells can develop into many cell types.

Which animals undergo indeterminate cleavage?

Deuterostomes.

Schizocoely

Formation of the coelom by splitting the mesoderm.

Schizocoely occurs in which animals?

Most protostomes.

Enterocoely

Formation of the coelom from pouches pinched off the gut.

Enterocoely occurs in which animals?

Deuterostomes.

Phylogeny

Evolutionary history and relationships among organisms.

Phylogenetic tree

Diagram showing evolutionary relationships.

Sources used to build phylogenies

Morphology, fossils, DNA, RNA, and protein analyses.

Morphological data

Physical characteristics used to compare organisms.

Molecular data

DNA, RNA, and protein evidence used to determine evolutionary relationships.

Choanoflagellates

Protists believed to closely resemble the ancestors of animals.

Choanocytes

Sponge feeding cells similar to choanoflagellates.

Closest living relatives of animals

Choanoflagellates.

Radiata

Group of radially symmetrical eumetazoans.

Bilateria

Group of bilaterally symmetrical animals.

Ecdysozoa

Protostomes that molt an exoskeleton.

Examples of Ecdysozoa

Arthropods and nematodes.

Ecdysis

Process of molting an exoskeleton.

Lophotrochozoa

Protostomes with trochophore larvae or a lophophore.

Examples of Lophotrochozoa

Annelids, mollusks, brachiopods.

Lophophore

Ciliated feeding structure found in some lophotrochozoans.

Trochophore

Free-swimming larval stage of many lophotrochozoans.

Importance of molecular evidence

Has significantly revised animal evolutionary relationships.

Ediacaran Period

Geological period from about 635–543 million years ago containing the earliest multicellular animals.

Ediacaran biota

Early multicellular organisms living before the Cambrian.

Cryogenian Period

Geological period before the Ediacaran characterized by global glaciation.

Cambrian Period

Period approximately 542–488 million years ago.

Cambrian Explosion

Rapid diversification of animal phyla during the Cambrian Period.

Significance of the Cambrian Explosion

Most modern animal phyla first appeared.

Possible causes of the Cambrian Explosion

Rising oxygen, ecological interactions, increased calcium, Hox gene evolution, and environmental changes.

Burgess Shale

Famous Cambrian fossil deposit preserving diverse animal life.

Trilobites

Extinct marine arthropods abundant during the Cambrian.

Why are trilobites important?

They are key index fossils for the Paleozoic Era.

Ordovician Period

Period following the Cambrian when plants first colonized land.

what is the largest mass extinction

End-Permian extinction.

Approximate species lost during the Permian extinction

About 95%.

Effect of the Permian extinction

Opened ecological niches for dinosaurs.

Mesozoic Era

Age of reptiles and dinosaurs.

End-Cretaceous extinction

Mass extinction that eliminated non-avian dinosaurs.

Likely cause of the end-Cretaceous extinction

Meteor impact combined with volcanic activity.

Cenozoic Era

Age of mammals.

Major animal group that diversified after dinosaurs

Mammals.