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Chapter 23: The Animal Kingdom Lecture Outline Enger, E. D., Ross, F. C., & Bailey, D. B. (2012). Concepts in biology (14th ed.). New York: McGraw-Hill. 1
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What is an animal?
Eukaryotic Multicellular
– Have specialized cells – Many have sensory cells that detect changes in
the environment. Lack cell walls Heterotrophic Most can move Most reproduce sexually
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Variety of Animals
See Figure 23.1
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The Evolution of Animals
Early animals were all aquatic. – The first animals were likely small organisms that
floated/swam in the ocean or worms that lived on the ocean floor.
– These animals didn’t need to Deal with rapid or extreme environmental changes Deal with dehydration Expend energy to keep cells in osmotic balance
Terrestrial animals appeared relatively recently. – Arthropods and vertebrates have been the most successful.
99.9% of all animals are invertebrates. – Invertebrates lack a backbone. – Vertebrates have a backbone.
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Animal Evolution
See Figure 23.2
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Temperature Regulation
Body temperature impacts the rate of metabolic activity.
Poikilotherms – Body temperature varies with environmental temperature – Metabolic rate decreases as temperature decreases – Also called ectotherms – Regulate body temperature behaviorally (sunning, moving) – Insects, worms, reptiles
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Temperature Regulation
Homeotherms – Maintain a constant body temperature – Body temperature usually higher than
environmental temperature – Have high metabolic rates – Have higher energy needs than poikilotherms – Also called endotherms
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Regulating Body Temperature
See Figure 23.3
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Body Plans
Animal bodies conform to a few basic body plans.
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Symmetry
Asymmetry – No pattern to individual parts – Only occurs in sponges
Radial symmetry – Body constructed across a central axis – Dividing the body in any plane along that axis results in two
identical parts – These animals do not have a “head” – Starfish, jellyfish
Bilateral symmetry – Both sides of a single plane are mirror images – These animals have a head – Move head-first (cephalization)
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Radial and Bilateral Symmetry
See Figure 23.4
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Embryonic Cell Layers
Animals differ in the number of cell layers of which they are composed.
– These layers are established and most easily seen in the embryonic stage.
Sponges have no body layers. Diploblastic
– Two body layers Endoderm
– Gives rise to inner hollow layer involved in processing food Ectoderm
– Gives rise to outer protective layer
– Jellyfish
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Embryonic Cell Layers
Triploblastic – Have three layers
Endoderm – Gives rise to lining of digestive tract
Mesoderm – Gives rise to muscles and connective tissue
Ectoderm – Gives rise to skin and nervous system
– All other major groups are triploblastic.
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Embryonic Cell Layers
See Figure 23.5
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Body Cavities
Many animals have a body cavity that separates the outer body wall from the gut.
– Called a coelom
Acoelomate – Contain no body cavity – Sponges, jellyfish, and flatworms
Pseudocoelomate – Located between the lining of the gut and the outer body wall – Nematodes
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Body Cavities
Coelomate – This is the cavity that contains the digestive,
excretory, and circulatory organs. – Organs are held in place by sheets of connective
tissue called mesenteries. – The presence of the coelom allows for separation
of inner organs and body-wall muscles. – This allows the organ systems to be more
specialized.
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Body Cavities
See Figure 23.6
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Segmentation
Segmented animals have bodies that are separated into several units.
– These units run along the anterior to posterior axis of the animal.
Associated with specialization of body parts Annelids, arthropods, and chordates
– Annelid segments are all very similar. – Arthropods have specialized head segments.
Posterior segments have legs and appendages. – Chordate segments are most obvious in the vertebral
column and musculature.
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Segmentation
See Figure 23.7
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Skeletons
Skeletons are body parts that provide support. – Serves as a scaffolding for the attachment of
organs – Provides a place for muscles to attach – Most important in terrestrial animals
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Skeletons
Types of skeleton – Endoskeleton — internal
Vertebrates Grows as the animal grows
– Exoskeleton — external Arthropods Hard and jointed Shed and regenerated as animal grows
– Water skeletons Fluid-filled coeloms Compressed by muscles to facilitate movement
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Skeletons
See Figure 23.8
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Marine Lifestyles: Zooplankton
A mixture of different kinds of small animals Drift with currents Feed on phytoplankton and other
zooplankton 70% are crustaceans
– Copepods, krill, etc.
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Marine Lifestyles: Nekton
Includes many kinds of aquatic animals that can swim against the current – Go where they want to
Carnivores – Feed on plankton or other nekton
Jellyfish, squid, cuttlefish, shrimp, sharks, bony fish, turtles, sea snakes, aquatic birds, and mammals
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Marine Lifestyles: Benthic Animals
Bottom-dwelling animals Includes
– Segmented worms, clams, snails, lobsters, crabs, shrimp, starfish, sea urchins, several kinds of fish
Two types – Those that move to find food – Filter feeders
Attached to objects Are sessile Create currents with cilia or use appendages to draw food to
them
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Marine Lifestyles: Benthic animals
Reproduction is difficult for sessile animals because they cannot move. – Sperm swim to the eggs. – Fertilized egg develops into mobile larva
Enables sessile animals to disperse Uses a different source of food from adults to minimize
competition
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The Life Cycle of an Oyster
See Figure 23.9
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Primitive Marine Animals: Porifera
Similar to colonial protozoa Have two layers of cells
– All cells come in contact with the environment. – Each individual cell gets its nutrition directly from the water.
Adults are sessile (non-motile). Most are asymmetrical. Have spicules in a jelly-like material
– Spicules are made of calcium carbonate, silicon dioxide, or protein.
Reproduce asexually by fragmentation or budding Reproduce sexually by external fertilization
– Sperm and egg unite in the water – Fertilized egg develops into free-swimming ciliated larva
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Sponge Structure and Function
See Figure 23.10
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Primitive Marine Animals: Cnidaria
Jellyfish, corals, and sea anemones Have two layers of cells
– Jelly-like material in between cell layers Show radial symmetry Have a single opening that leads to digestive
cavity – Opening surrounded by tentacles
Contain specialized cells called nematocytes that can sting and paralyze
The cells that produce nematocytes are called cnidocytes.
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Phylum Cnidaria
See Figure 23.11
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Cnidaria
Exhibit alternation of generations
– Have both sexual and asexual reproduction
– Medusa is the free-swimming adult stage that reproduces sexually.
– Polyp is a sessile larval stage that reproduces asexually.
See Figure 23.12
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Ctenophora: The Comb Jellies
See figure 23-13
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Platyhelminthes
Also called flatworms Bilaterally symmetrical Triploblastic Lack a coelom Have one opening to the gut Have no circulatory or respiratory systems
– Their flat body allows for the diffusion of gases between environment and all cells.
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Platyhelminthes
Three basic types – Free-living flatworms (planarians)
Bottom-dwellers in aquatic environments Some live in moist terrestrial habitats Carnivores or scavengers that feed on dead organisms
– Flukes Parasitic
– Tapeworms Parasitic
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Platyhelminthes
See figure 23.14
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Flukes
All are parasites (some external, most internal). Life cycles usually involve a vertebrate and
invertebrate host. Example: Schistosoma mansoni
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Life Cycle of Schistosoma mansoni
See figure 23.15
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Tapeworms
All are parasites. Life cycles involve two hosts—an herbivore
and a carnivore (both vertebrates).
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Life Cycle of a Tapeworm
See figure 23.16
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Nematoda
Also called roundworms Unsegmented Have an outer epidermis covered by a thick, flexible
cuticle Triploblastic Have a pseudocoelom Digestive tract is open at two ends
– Mouth at one end, anus at the other Live in diverse habitats
– Water, soil, as parasites Examples of parasitic forms
– Pinworms, heartworms, hookworms
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Nematode Worms
See Figure 23.17
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The Life Cycle of a Hookworm
See Figure 23.18
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Annelida
Segmented worms Bilaterally symmetrical Have bodies with repeating segments
– Most segments are similar to one another. – Segments containing head, reproductive, and digestive
structures are specialized.
Each segment has a coelom. Have well-developed muscular, circulatory,
digestive, excretory, and nervous systems
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Annelida
See figure 23.19
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Types of Annelida
Polychates – Primarily benthic, marine worms – Have paddle-like appendages on each segment – Have heads with sense organs and a mouth – Are filter feeders – Have separate sexes that reproduce sexually
Produce larva called trochophores
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Types of Annelida
Oligochates – Live in soil or freshwater – Earthworms – Do not have appendages or a well-defined head – Are hermaphroditic – Eat dead organic matter, generate air spaces in
soil
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Types of Annelida
Leeches – Live in freshwater or moist terrestrial
environments – Have suckers that allow them to hold on to
objects – Feed on the blood of vertebrates
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Annelids
See Figure 23.20
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Mollusca
Live in marine, freshwater, or terrestrial environments – Majority live in the ocean
Have a coelom Reproduce sexually
– Some are hemaphroditic Have a soft body enclosed by a hard shell
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Mollusca
Most are slow moving, benthic animals Most are herbivores or saprophytes Have free-living larval forms that aid in dispersal Have three body regions
– Mantle, foot, and visceral mass – Visceral mass contains digestive, circulatory, and
reproductive organs. – Most have a radula with teeth.
Used to scrape surfaces for food
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Mollusca
See figure 23.21
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Types of Mollusca
Chitons – Have a series of shells on their backs – Live attached to rocks – Feed on algae
Bivalves – Have two shells – Filter feeders without a radula
Snails – Have coiled shells – Slugs are snails without shells
Octopus and squid – No outer shell
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Types of Mollusca
See figure 23.22
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Arthropoda
Most successful types of animals Have exoskeletons made of chitin
– Must shed to grow Have segmented bodies
– Segments are highly modified. – Most segments have paired appendages. – Body and appendages are segmented.
Have well-developed nervous, muscular, digestive, respiratory, circulatory, and reproductive systems
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Arthropoda
See figure 23.23
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Types of Arthropods
Crustaceans – All aquatic – Omnivores
Millipedes and centipedes – Long bodies with many legs
Arachnids – Spiders, mites, and ticks
Insects – Have a head, thorax, and abdomen – Have 3 pairs of legs – Most have wings
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Arthropods
See Figure 23.24
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Echinodermata
Are dueterostomates – Anus develops before mouth
All are marine, benthic animals Most are free-living Most are carnivores or detrivores
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Echinodermata
Display radial symmetry – Have five arms that project from a central axis – Larva display bilateral symmetry.
Have a water vascular system – Water is taken through a pore on the top, then
moves through a series of canals. – Aids in movement of the animal
Have a hard, jointed internal skeleton
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Echinoderms
See Figure 23.25
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Types of Echinoderms
Starfish – Some are carnivores that
eat clams
Sea cucumbers – Sausage-shaped
organisms – Lie on the bottom or
burrow in mud – Some are detrivores,
others are filter-feeders.
Crinoids – Sessile and stalked – Have five arms – Called sea lilies – Filter feeders
Brittlestars Sea urchins
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Types of Echinoderms
See figure 23.26
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Chordata
Have a hollow nerve cord down the back of the body
Have a flexible rod just beneath the nerve cord – Called the notochord
Have a tail that extends beyond the anus Have a pharynx Most are vertebrates
– Notochord only present during embryonic stage
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Invertebrate Chordates
See Figure 23.27
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Types of Aquatic Vertebrates: Fishes
Hagfish and lampreys are the most primitive fish.
– Hagfish are marine scavengers.
– Lampreys are mainly marine (some freshwater). Adults suck blood
from larger fish.
See Figure 23.28
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Types of Aquatic Vertebrates: Fishes
Sharks and rays – Have an internal
skeleton made of cartilage
– Have no swim bladder, so must constantly swim or they sink
– Rays feed along bottom. – Sharks are predatory.
See Figure 23.29
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Types of Aquatic Vertebrates: Fishes
Bony fish – Have skeletons
composed of bones – Have a swim bladder
that controls their density Allows them to
remain at a given depth without swimming
See Figure 23.30
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Adaptations to Terrestrial Life
Animals that live on land have to overcome certain problems. – A moist membrane for gas exchange – Means of support and locomotion on land – Methods to conserve water – Means of reproduction and embryonic
development that doesn’t require water – Methods to survive rapid and extreme climate
changes
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Terrestrial Arthropods
Exoskeleton – Waterproof, which
reduces water loss Have an internal
respiratory system – Tracheal system of thin-
walled tubes – Provides a large surface
area for gas-exchange – Have small openings to
the outside, reducing water loss
See Figure 23.31
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Terrestrial Arthropods
Have Malpighian tubules – Thin-walled tubes that surround the gut – Allows for reabsorption of water
Reproduce by internal fertilization – Protects sperm and egg from drying out
Can reproduce rapidly when conditions become favorable
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The Life History of a Monarch Butterfly
See Figure 23.32
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Terrestrial Vertebrates
Endoskeleton – Provides support in the air – Provides places for muscle attachment
Allows for movement on land
Appendages are necessary for movement on land.
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Amphibians
Lungs – Allow for the exchange of oxygen and carbon
dioxide from the air – Amphibians also breathe through their skin.
Skin must remain moist
External reproduction in water Frogs and salamanders
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Amphibians
See Figure 23.33
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Reptiles
Have internal lungs Have waterproof skin Have water-conserving
kidneys Reproduce via internal
fertilization – Fertilized egg is encased
in an amniotic egg – Protects the young from
dehydration and injury Young need water to
develop.
See Figure 23.34
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Reptiles
See Figure 23.35
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Birds
Skin, lungs, and kidneys reduce water loss Reproduction involves internal fertilization.
– Produces a shelled amniotic egg
Are homeothermic and have feathers – Have high metabolic rates – Feathers insulate and enable flight. – Must incubate eggs
Flight allows – Movement with less expenditure of energy – Quick escape from predators – Ability to cross barriers
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Birds
See Figure 23.36
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Mammals
Homeotherms – High, constant body temperature – High metabolic rate
Have waterproof skin, water-conserving lungs and kidneys
Have hair as insulation Provide milk to their young
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Types of Mammals
Monotremes – Egg-laying mammals – Young lap milk from mother’s fur
Marsupials – Internal development of young – Young complete development in mother’s pouch
In pouch, young drink milk from nipple
Placental – Internal development of young
Stay in mother longer Embryo attached to uterus via a placenta
– Young are born in a more advanced stage Still rely on mother’s milk
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Mammals
See Figure 23.37