Animal Diversity and Classification Overview

Animal species

Over a million described, many undiscovered.

Invertebrates

Animals without a backbone, majority of species.

Extinct species

Up to 99% of all species are extinct.

Vertebrates

Only 5% of animals, have backbones.

Definition of animal

Multicellular, heterotrophic eukaryotes with tissue layers.

Heterotrophic

Organisms that ingest organic molecules for nutrition.

Cell walls

Absent in animal cells, unlike plants and fungi.

Extracellular proteins

Collagen holds multicellular animal bodies together.

Nervous tissue

Specialized for impulse conduction in animals.

Muscle tissue

Specialized for movement in animals.

Sexual reproduction

Most animals reproduce with a dominant diploid stage.

Zygote

Fertilized egg that undergoes cleavage.

Blastula

Multicellular, hollow ball of cells post-cleavage.

Monophyletic

Animal kingdom evolved from a common ancestor.

Colonial flagellated protist

Common ancestor of animals, lived 770 million years ago.

Choanoflagellates

Related to the ancestor, tiny stalked organisms.

Evolution hypothesis

Cells evolved into a hollow sphere, specialized layers.

Autotrophic

Plants generate organic molecules via photosynthesis.

Exoenzymes

Fungi digest food externally, unlike animals.

Glycogen

Carbohydrate storage in animals, unlike starch in plants.

Impulse conduction

Function of nervous tissue in animals.

Structural adaptation

Features like proboscis for feeding in animals.

Biology's major themes

Animal form and function reflect evolutionary challenges.

Oxygen extraction

Essential challenge for all animals' survival.

Waste excretion

Critical process for animal health and homeostasis.

Proboscis

Moth's straw-like structure for nectar feeding.

Natural Selection

Mechanism for long-term adaptation in organisms.

Physiological Responses

Short-term adjustments to environmental changes.

Hawkmoth

Can forage at temperatures as low as 5°C.

Shivering Mechanism

Preflight warm-up for moth flight muscles.

Muscle Temperature

Maintained at 30°C during flight activity.

Phylogenetic Tree

Diagram showing evolutionary relationships among animals.

Parazoa

Animals lacking true tissues, like sponges.

Eumetazoa

Animals with true tissues, including most phyla.

Cnidaria

Phylum with radial symmetry; includes jellies and anemones.

Ctenophora

Phylum of comb jellies with radial symmetry.

Bilateria

Animals with bilateral symmetry and complex structures.

Cephalization

Concentration of sensory organs at the head.

Bilateral Symmetry

Body plan with distinct left and right sides.

Germ Layers

Embryonic tissue layers forming organs and tissues.

Diploblastic

Organisms with two germ layers: ectoderm and endoderm.

Triploblastic

Organisms with three germ layers, including mesoderm.

Mesoderm

Third germ layer developing into muscles and organs.

Acoelomates

Solid-bodied animals lacking a body cavity.

Pseudocoelomates

Animals with a body cavity not fully lined by mesoderm.

Coelomates

Organisms with a true coelom lined by mesoderm.

Mesenteries

Tissue connecting and suspending internal organs.

Hydrostatic Skeleton

Fluid-filled cavity providing structural support for muscles.

Coelom

Body cavity allowing organ movement and growth.

Coelomate Phyla

Divided into protostomes and deuterostomes.

Protostomes

Includes mollusks, annelids, and arthropods.

Deuterostomes

Includes echinoderms and chordates.

Cleavage Pattern

Arrangement of cells during early embryo development.

Spiral Cleavage

Cell division planes diagonal to embryo's vertical axis.

Determinate Cleavage

Early cell fate is predetermined in development.

Radial Cleavage

Cell division planes parallel or perpendicular to egg axis.

Indeterminate Cleavage

Early cells can develop into complete embryos.

Gastrula Stage

Stage where coelom formation begins.

Schizocoelous Development

Coelom forms from solid mesoderm masses.

Enterocoelous Development

Coelom forms from mesoderm buds off archenteron.

Blastopore

Opening of the archenteron in embryonic development.

Protostome Blastopore Fate

Blastopore develops into mouth.

Deuterostome Blastopore Fate

Blastopore develops into anus.

Phylum Porifera

Includes sponges, characterized by porous bodies.

Choanocytes

Flagellated cells that create water flow in sponges.

Mesohyl

Gelatinous region between cell layers in sponges.

Amoebocytes

Cells that transport nutrients and secrete fibers.

Spicules

Sharp skeletal fibers made of calcium carbonate or silica.

Spongin

Flexible fibers made of collagen in some sponges.

Hermaphrodites

Organisms producing both sperm and eggs.

Regeneration

Ability to replace lost parts in sponges.

Radiata

Oldest eumetazoan clade with radial symmetry.

Phylum Cnidaria

Includes hydras, jellies, sea anemones, and corals.

Radial symmetry

Body plan where body parts radiate from center.

Gastrovascular cavity

Central digestive compartment in cnidarians.

Cnidocytes

Specialized cells for capturing prey in cnidarians.

Polyp

Sessile form of cnidarians, adheres to surfaces.

Medusa

Free-floating, bell-shaped form of cnidarians.

Nematocysts

Stinging capsules within cnidocytes for defense.

Hydrozoa

Class of cnidarians with alternating life stages.

Scyphozoa

Class where medusa form predominates in life cycle.

Anthozoa

Class including sea anemones and corals, only polyps.

Cubozoa

Class of box jellyfish, advanced nervous system.

Budding

Asexual reproduction method in hydras, forming outgrowths.

Zygotes

Dormant forms produced by hydras under stress.

Contractile fibers

Microfilaments in cnidarians enabling movement.

Nerve net

Noncentralized nerve system in cnidarians.

Coral reefs

Habitat formed by calcium carbonate skeletons of corals.

Environmental changes

Factors like global warming damaging coral reefs.

Flatworms

Acoelomates with gastrovascular cavities, diverse habitats.

Parasitic species

Flatworms like flukes and tapeworms that live off hosts.

Species diversity

Over 10,000 cnidarian species, mostly marine.

Life cycle variations

Cnidarians may alternate between polyp and medusa stages.

Classes of Flatworms

Includes Turbellaria, Monogenia, Trematoda, Cestoidea.

Turbellarians

Mostly free-living, nonparasitic flatworms.

Planarians

Carnivorous flatworms from genus Dugesia.

Gas exchange

Flatworms lack specialized organs for this.

Diffusion

Method for nitrogenous waste removal in flatworms.

Ciliated flame cells

Help maintain osmotic balance in flatworms.

Movement of Planarians

Use cilia and mucus for gliding.