AP Biology

Lecture #49Non-Vertebrate Animals

Characteristics of Animals

• Animals are:• Multicellular• Heterotrophs• Eukaryotic• Have tissues and differentiated cells• Eat• Reproduce and Develop• 1.3 millions species have been identified,

estimates of 10 to 200 million exist

Early Embryonic Development• Sperm and egg meet

through fertilization to form a zygote

• The zygote undergoes mitosis, called cleavage

• A blastula, or multi-celled hollow ball forms

• These cells form tissue layers that make up a gastrula

Eras of Animal Life

• Neoproterozoic Era (1 B 542 mya): First fossilized animals are from this time period.

• Paleozoic Era (542 251 mya): the Cambrian explosion occurs, huge diversity of animal species, including vertebrates, evolve

• Mesozoic Era (251 65.5 mya): animal life spreads across the planet

• Cenozoic Era (65.5 mya present): dinosaurs, birds, and mammals all evolve

Body Plans

• Animals can have radial symmetry, in which the parts of an animal radiate out from the center (starfish)

• Or they can have bilateral symmetry, with equal left and right sides (lobsters, humans)

• Animals with a distinct forward facing head at the top of the body have gone through cephalization.

Tissue Layers• The tissue layers of an animal

embryo are called germ layers, and form organs.

• The ectoderm is the outermost layer and forms the skin and nervous system.

• The endoderm is the inner layer of the embryo and turns into the digestive system.

• Some animals have a third layer, called the mesoderm, which forms the other body organs.

Body Cavities

• Some animals have body cavities, a fluid-filled space that separates the digestive tract from the outer body wall, this is called a coelom.

• Pseudocoelomates have a body cavity that is formed from a different type of tissue.

• Acoelomates do not have body cavities.

Protostomes and Deuterostomes• Protostomes, like

worms and bugs, develop a mouth first during fetal development.

• Deuterostomes, like people and starfish, develop an anus before they develop mouths.

Invertebrates

• Invertebrates are animals without a backbone.• The main phyla we will talk about are:

– Porifera– Cnidaria– Platyhelminthes– Nemotodes– Mollusks– Annelids– Arthropods– Echinodermata– Some chordates

Invertebrates

Parazoa

• Invertebrates: animals without backbones

• Closest lineage to protists

• Loose federation of cells (unspecialized); no tissues

• Phylum.: (only one) Porifera (sponges)

The Sponges – Phylum Porifera

• Phylum Porifera are the sponges.• They may have radial symmetry, or no

symmetry.• They are non-motile filter feeders.• Individual cells are specialized, but they have

no true organs.

Phylum Porifera

General InformationSize range – 1 cm to2 meters in diameter

Giant Barrel sponges

Eumetazoa: Animals with true body tissueThe Radiata, I

• Diploblastic• Radial symmetry• Phylum: Cnidaria (hydra, jellies, sea

anemones, corals)– tissues, but no organs– two cell layers– predators

• tentacles surround gut opening

• extracellular digestion– release enzymes

into gut cavity– absorption by cells

lining gut

hydra

stinging cellwith nematocyst

trigger

dischargednematocyst

undischargednematocyst

tentacles

mouth

sensorycell

stingingcell

Stinging cells of Cnidarians

The Radiata, II

• Phylum: Ctenophora (comb jellies)

• 8 rows of comblike plates of fused cilia (largest animals that use cilia for locomotion)

• Tentacles with colloblasts (adhesive structures that capture prey)

Eumetazoa: The Acoelomates• Phy: Platyhelminthes

(flatworms, flukes, tapeworms)

• Bilateral; no body cavity• Predators, scavengers,

parasites• Some cephalization~

development of brain concentration of sense organs in head

ectoderm

mesoderm

endodermacoelomate

Eumetazoa: Pseudocoelomates, I

• Body cavity partially derived from mesodermally derived tissue

• Phylum: Rotifera• 1st with a complete

digestive tract• Hydrostatic skeleton• Parthenogenesis: type of

reproduction in which females produce offspring from unfertilized eggs

Eumetazoa: Pseudocoelomates, II

• Phylum: Nematoda (roundworms)

• Very widespread group of animals (900,000 sp. ?)

• Cuticle (tough exoskeleton)• Decomposition and nutrient

cycling• Complete digestive track; no

circulatory systemmany are parasitic

• hookworm• Trichinella spiralis

C. elegans

The Coelomates: Protostomes, I

• Phylogenetics debated….• Phy: Nemertea (proboscis and

ribbon worms)• Complete digestion and closed

circulatory system (blood)• Phy: the lophophorates (sea

mats, tube worms, lamp shells)• Lophophore: Circular shaped

body fold with ciliated tentacles around the mouth

The Coelomates: Protostomes, II• Phylum: Mollusca (snails,

slugs, squid, octopus, clams, oysters, chiton)

• Soft body most protected by a hard shell of calcium carbonate

• Foot (movement), visceral mass (internal organs); mantle (secretes shell); radula (rasp-like scraping organ)true coelem• increases complexity &

specialization of internal organs

• There are 3 types of mollusks:• Gastropods: sea slugs, snails and slugs• Bivalves: clams, oysters, mussels, and scallops

(2 hinged shells)• Cephalopods: built for speed and motility,

include squid and octopi; have sophisticated sense organs.

Phylum Mollusca

Class Cephalopoda squids, octopus, cuttlefish, nautilus

The Coelomates: Protostomes, III• Phylum: Annelida

(earthworms, leeches, marine worms)

• True body segmentation (specialization of body regions)

• Closed circulatory system• Metanephridia: excretory

tubes• “Brainlike” cerebral

ganglia• Hermaphrodites, but

cross- fertilize

leechfan worm

The Coelomates: Protostomes, IV• Phy: Arthropoda trilobites

(extinct); crustaceans (crabs, lobsters, shrimps); spiders, scorpions, ticks (arachnids); insects (entomology)

• 2 out of every 3 organisms (most successful of all phyla)

• Segmentation, hard exoskeleton (cuticle)~ molting, jointed appendages; open circulatory system (hemolymph); extensive cephalization

Arthropod groups

insects6 legs, 3 body parts

crustaceansgills, 2 pairs antennaecrab, lobster, barnacles, shrmp

arachnids8 legs, 2 body partsspiders, ticks, scorpions

The Coelomates: Deuterostomes, I

• Phylum: Echinodermata (sea stars, sea urchins, sand dollars, sea lilies, sea cucumbers, sea daisies)

• Spiny skin; sessile or slow moving

• Often pentaradial• Water vascular system• They are radially symmetrical

as adults, and bilateral as larvae.

Water Vascular System

• Madreporite• stone canal• ring canal• radial canal• lateral canals• Ampulae• tube feet