Introduction to Animal Biology

Introduction to Animal Biology

• Personal experience revealed Biology is more than just animals; cells, cell division, genetics, and evolution.
• Despite broad biology training, specific animal study came later in zoology courses.
• Initial fascination with animals drives continued interest in biology.
• Understanding varied biological content enhances animal comprehension.

Defining Characteristics of Animals

• Animals include diverse organisms beyond common perceptions, such as ants and sponges.
• Key shared traits: multicellular, eukaryotic cells, specialized cells.
• Most animals feature cells organized into specialized tissues.
• Animals are heterotrophs, requiring consumption of food.
• Distinct from fungi: animals ingest organic matter, while fungi digest externally and absorb nutrients.
• Most animals exhibit motility at some stage of their life cycle.

Important Vocabulary in Animal Biology

• Symmetry is a key feature, radial symmetry means multiple planes can divide into similar portions.
• Radial symmetry is useful for sessile organisms, enabling multi-directional environmental response.
• Bilateral symmetry has a line down the middle creating similar halves.
• Bilateral symmetry is advantageous for forward movement.

Cephalization and Embryonic Development

• Cephalization in bilaterally symmetrical animals: nervous system concentrated in head.
• Cephalization benefits: mouth and sensory organs located together in the head region.
• Triploblastic animals can be categorized as protostomes or deuterostomes during development.
• Protostomes: first embryonic opening (blastopore) develops into the mouth, second forms the anus.
• Deuterostomes: first blastopore opening becomes the anus, second opening forms the mouth.
• Mnemonic: "M" (mouth) is paired with "P" (protostome); "A" (anus) with "D" (deuterostome).

Germ Layers and Coelom

• Triploblastic animals: possess three germ layers (ectoderm, endoderm, mesoderm).
• Germ layers form different animal structures: ectoderm, endoderm, and mesoderm.
• Diploblastic animals: lack the mesoderm layer, are neither protostomes nor deuterostomes.
• Coelom: body cavity derived from mesoderm, filled with fluid, acts as space for organs.
• Coelom functions: shock absorption, cushioning, and organ development space.
• Animal classification depends on the presence or absence of a true coelom.

Animal Phyla Overview

• Overview of 9 major animal phyla, acknowledging exceptions may exist.
• Phylum Porifera: Includes sponges, aquatic, primarily saltwater, sessile adults.
• Porifera bodies characterized by pores for water, oxygen, and food passage.
• Porifera intracellular digestion inside their cells.
• Porifera lack a gut, organs, and true tissues, without symmetry (some radial exceptions), cephalization, and coelom.
• Phylum Cnidaria: Includes jellies, sea anemones, and hydras, aquatic, saltwater and freshwater.
• Cnidaria has a single gut opening acting as mouth and anus, intracellular and extracellular digestion.
• Cnidaria has polyp and medusa forms.
• Cnidaria have specialized cells with organelles to sting prey.
• Cnidaria exhibit radial symmetry, without cephalization and coelom.
• Phylum Platyhelminthes: Flatworms, aquatic (fresh/saltwater), terrestrial, includes planarians and tapeworms.
• Platyhelminthes features parasitic species, one gut opening, bilateral symmetry, cephalization, and no coelom.
• Platyhelminthes; protostomes

More Animal Phyla

• Phylum Nematoda: Nematodes, hookworms, and pinworms, significant ecological impact
• Nematoda infest crops and parasitize nearly all animals; beneficial to soil ecology.
• Nematoda generally small, live in aquatic and terrestrial environments.
• Nematoda has bilateral symmetry, cephalization, pseudocoelom, protostomes, two gut openings (mouth and anus).
• Phylum Mollusca: Mollusks, micromullusks to giant squid, snails, clams, octopuses.
• Mollusca has mainly aquatic (salt/freshwater), some terrestrial, secrete shells from the mantle.
• Mollusca possess a radula (tongue-like for scraping food) and muscular foot for movement.
• Mollusca symmetry is bilateral, cephalization, coelom, protostomes.
• Phylum Annelida: Annelids, earthworms, leeches, tubeworms; aquatic and terrestrial.
• Annelida segmented bodies/repeating parts, setae (hair-like) for movement/anchoring.
• Annelida has bilateral symmetry, cephalization, coelom, protostomes.
• Phylum Arthropoda: Arthropods, insects, spiders, crustaceans; aquatic and terrestrial (many fly).
• Arthropoda has jointed appendages, segmented bodies, protective exoskeleton.
• Arthropoda larva to adult metamorphosis enable varied resource use.
• Arthropoda has bilateral symmetry, cephalization, coelom, protostomes.
• Phylum Echinodermata: Echinoderms, sea stars, sea urchins, sea cucumbers, saltwater aquatic.
• Echinodermata larvae have bilateral symmetry, adults have radial symmetry.
• Echinodermata can regenerate and reproduce asexually from lost parts.
• Echinodermata lacks cephalization and a brain, but has a coelom and are deuterostomes.

Vertebrates vs. Invertebrates

• Most animal species are invertebrates (approx. 97%), lacking a vertebral column/spine.
• Phylum Chordata: Chordates, vertebrates like fish, amphibians, reptiles, birds, and mammals.
• Chordata defined by notochord which is a flexible rod along the back.
• Notochord presence indicates chordates.
• Chordata has other features: dorsal nerve cord, pharyngeal slits/pouches, postanal tail, thyroid gland.
• Chordata live in aquatic and terrestrial habitats (some fly), exhibit segmented bodies.
• Chordata has bilateral symmetry, cephalization, coelom, deuterostomes.