Download What Is an Animal?

Chapter 17
The Evolution of Animals
PowerPoint® Lectures for
Campbell Essential Biology, Fourth Edition
– Eric Simon, Jane Reece, and Jean Dickey
Campbell Essential Biology with Physiology, Third Edition
– Eric Simon, Jane Reece, and Jean Dickey
Lectures by Chris C. Romero, updated by Edward J. Zalisko
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Domain Bacteria
Earliest
organisms
Domain Archaea
The protists
(multiple
kingdoms)
Kingdom
Plantae
Domain Eukarya
The three-domain
classification
system
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Kingdom
Fungi
Kingdom
Animalia
Figure 14.25
What Is an Animal?
• Animals are:
– Eukaryotic
– Multicellular
– Heterotrophic organisms that obtain nutrients by ingestion
– Able to digest their food within their bodies
• Animal cells lack the cell walls that provide strong support in the
bodies of plants and fungi.
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• Most animals have:
– Muscle cells
– Nerve cells that control the muscles
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• Most animals:
– Are diploid
– Reproduce sexually
– Proceed through a series of typically similar developmental stages
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Early Animals and the Cambrian Explosion
• Animals probably evolved from a colonial flagellated protist that
lived in Precambrian seas about 600–700 million years ago.
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• At the beginning of the Cambrian period, 542 million years ago,
animals underwent a rapid diversification.
• During a span of about 15 million years:
– All major animal body plans we see today evolved
– Many of these animals seem bizarre
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Figure 17.4a
Animal Phylogeny
• Biologists categorize animals by:
– General features of body structure
– More recently, using genetic data
• One major branch point distinguishes sponges from all other
animals because, unlike more complex animals, sponges lack true
tissues.
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Sponges
• Sponges represent multiple phyla.
• Sponges include sessile animals that lack true tissues and that
were once believed to be plants.
• The body of a sponge resembles a sac perforated with holes.
• Choanocyte cells draw water through the walls of the sponge
where food is collected.
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Pores
Amoebocyte
Skeletal
fiber
Central
cavity
Choanocyte
(feeding cell)
Water
flow
Flagella
Choanocyte
in contact
with an
amoebocyte
Figure 17.8
MAJOR INVERTEBRATE PHYLA
• Invertebrates:
– Are animals without backbones
– Represent 95% of the animal kingdom
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Sponges
No true tissues
Cnidarians
Radial symmetry
Ancestral
protist
Molluscs
Flatworms
Tissues
Annelids
Roundworms
Arthropods
Bilateral symmetry
Echinoderms
Chordates
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Figure 17.5
• A second major evolutionary split is based on body symmetry.
– Radial symmetry refers to animals that are identical all around a central
axis.
– Bilateral symmetry exists where there is only one way to split the
animal into equal halves.
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Radial symmetry. Parts radiate from the center, so any slice
through the central axis divides into mirror images.
Bilateral symmetry. Only one slice can divide left and right
sides into mirror-image halves.
Figure 17.6
Sponges
No true tissues
Cnidarians
Radial symmetry
Ancestral
protist
Molluscs
Flatworms
Tissues
Annelids
Roundworms
Arthropods
Bilateral symmetry
Echinoderms
Chordates
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Figure 17.5
Cnidarians
• Cnidarians (phylum Cnidaria) are characterized by:
– The presence of body tissues
– Radial symmetry
– Tentacles with stinging cells
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• The basic body plan of a cnidarian is a sac with a gastrovascular
cavity, a central digestive compartment with only one opening.
• The body plan has two variations:
– The sessile polyp
– The floating medusa
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Mouth/anus
Tentacle
Gastrovascular
cavity
Polyp form
Coral
Hydra
Sea anemone
Gastrovascular
cavity
Mouth/anus
Tentacle
Medusa form
Jelly
Figure 17.9
• Cnidarians are carnivores that use tentacles, armed with
cnidocytes (“stinging cells”), to capture prey.
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Sponges
No true tissues
Cnidarians
Radial symmetry
Ancestral
protist
Molluscs
Flatworms
Tissues
Annelids
Roundworms
Arthropods
Bilateral symmetry
Echinoderms
Chordates
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Figure 17.5
Molluscs
• Molluscs (phylum Mollusca) are represented by soft-bodied
animals, usually protected by a hard shell.
• Many molluscs feed by using a file-like organ called a radula to
scrape up food.
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• The body of a mollusc has three main parts:
– A muscular foot used for movement
– A visceral mass housing most of the internal organs
– A mantle, which secretes the shell if present
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MAJOR GROUPS OF MOLLUSCS
Gastropods
Bivalves
(hinged shell)
Cephalopods
(large brain and tentacles)
Snail (spiraled shell)
Scallop
Octopus
Squid
Sea slug (no shell)
Figure 17.12
Sponges
No true tissues
Cnidarians
Radial symmetry
Ancestral
protist
Molluscs
Flatworms
Tissues
Annelids
Roundworms
Arthropods
Bilateral symmetry
Echinoderms
Chordates
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Figure 17.5
Flatworms
• Flatworms (phylum Platyhelminthes) are the simplest bilateral
animals.
• Flatworms include forms that are:
– Parasites or
– Free-living in marine, freshwater, or damp habitats
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Blood fluke
Reproductive unit
with skin removed
Head
Hooks
Suckers
Tapeworm
Figure 17.13b,c
• The gastrovascular cavity of flatworms
– Is highly branched
– Provides an extensive surface area for absorption of nutrients
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Digestive tract
(gastrovascular
cavity)
Nerve cords
Mouth
Eyespots (detect light)
Nervous tissue clusters
(simple brain)
Planarian
Bilateral symmetry
Figure 17.13a
Annelids
• Annelids (phylum Annelida) have:
– Body segmentation, a subdivision of the body along its length into a
series of repeated parts
– A complete digestive tract with
–
Two openings, a mouth and anus
–
One-way movement of food
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Anus
Brain
Main
heart
Coelom
Digestive
tract
Segment
walls
Mouth
Accessory
hearts
Nerve cord
Waste disposal organ
Blood vessels
Figure 17.15
• The three main groups of annelids are:
– Earthworms, which eat their way through soil
– Polychaetes, marine worms with segmental appendages for movement
and gas exchange
– Leeches, typically free-living carnivores but with some bloodsucking
forms
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MAJOR GROUPS OF ANNELIDS
Earthworms
Polychaetes
Leeches
Giant Australian earthworm
Christmas tree worm
European freshwater leech
Figure 17.14
Roundworms
• Roundworms (phylum Nematoda) are:
– Cylindrical in shape, tapered at both ends
– The most diverse and widespread of all animals
• Roundworms (also called nematodes) are:
– Important decomposers
– Dangerous parasites in plants, humans, and other animals
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(a) A free-living
roundworm
(b) Parasitic
roundworms in pork
(c) Canine heart
Infected with parasitic
roundworms
Figure 17.16
Sponges
No true tissues
Cnidarians
Radial symmetry
Ancestral
protist
Molluscs
Flatworms
Tissues
Annelids
Roundworms
Arthropods
Bilateral symmetry
Echinoderms
Chordates
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Figure 17.5
Arthropods
• Arthropods (phylum Arthropoda) are named for their jointed
appendages.
• There are about one million arthropod species identified, mostly
insects.
• Arthropods are a very diverse and successful group, occurring in
nearly all habitats in the biosphere.
• There are four main groups of arthropods.
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MAJOR GROUPS OF ARTHROPODS
Arachnids
Crustaceans
Millipedes and Centipedes
Insects
Figure 17.17
General Characteristics of Arthropods
• Arthropods are segmented animals with specialized segments and
appendages for an efficient division of labor among body regions.
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• The body of arthropods is completely covered by an exoskeleton,
an external skeleton that provides:
– Protection
– Points of attachment for the muscles that move appendages
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Abdomen
Cephalothorax
(head and thorax)
Antenna
(sensory reception)
Eyes on
movable stalks
Mouthparts (feeding)
Walking leg
Swimming
appendage
Walking legs
Figure 17.18
Arachnids
• Arachnids:
– Live on land
– Usually have four pairs of walking legs and a specialized pair of feeding
appendages
– Include spiders, scorpions, ticks, and mites
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Two feeding
appendages
Leg (four pairs)
Scorpion
Black widow spider
Dust mite
Wood tick
Figure 17.19
Crustaceans
• Crustaceans:
– Are nearly all aquatic
– Have multiple pairs of specialized appendages
– Include crabs, lobsters, crayfish, shrimps, and barnacles
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Two feeding
appendages
Leg (three or more pairs)
Antennae
Crab
Shrimp
Crayfish
Pill bug
Barnacles
Figure 17.20
Millipedes and Centipedes
• Millipedes and centipedes have similar segments over most of the
body.
• Millipedes:
– Eat decaying plant matter
– Have two pairs of short legs per body segment
• Centipedes:
– Are terrestrial carnivores with poison claws
– Have one pair of short legs per body segment
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One pair of legs per segment
Two pairs of legs
per segment
Millipede
Centipede
Figure 17.21
Insect Anatomy
• Insects typically have a three-part body:
– Head
– Thorax
– Abdomen
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• The insect head usually bears:
– A pair of sensory antennae
– A pair of eyes
• The mouthparts are adapted for particular kinds of eating.
• Flight is one key to the great success of insects.
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Head Thorax
Abdomen
Antenna
Eye
Mouthparts
Figure 17.22
Insect Diversity
• Insects outnumber all other forms of life combined.
• Insects live in:
– Almost every terrestrial habitat
– Freshwater
– The air
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• Many insects undergo metamorphosis in their development.
• Young insects may:
– Appear to be smaller forms of the adult or
– Change from a larval form to something much different as an adult
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The larva (caterpillar) spends
its time eating and growing,
molting as it grows.
Figure 17.24-1
The larva (caterpillar) spends
its time eating and growing,
molting as it grows.
After several molts, the
larva becomes a pupa
encased in a cocoon.
Finally, the adult emerges
from the cocoon.
Within the pupa, the larval organs break
down and adult organs develop from
cells that were dormant in the larva.
The butterfly flies off and reproduces, nourished mainly
by calories stored when it was a caterpillar.
Figure 17.24-5
Sponges
No true tissues
Cnidarians
Radial symmetry
Ancestral
protist
Molluscs
Flatworms
Tissues
Annelids
Roundworms
Arthropods
Bilateral symmetry
Echinoderms
Chordates
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Figure 17.5
Echinoderms
• Echinoderms (phylum Echinodermata):
– Lack body segments
– Typically show radial symmetry as adults but bilateral symmetry as
larvae
– Have an endoskeleton
– Have a water vascular system that facilitates movement and gas
exchange
• Echinoderms are a very diverse group.
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Sea star
Tube feet
Sea urchin
Sea cucumber
Sand dollar
Figure 17.25
Sponges
No true tissues
Cnidarians
Radial symmetry
Ancestral
protist
Molluscs
Flatworms
Tissues
Annelids
Roundworms
Arthropods
Bilateral symmetry
Echinoderms
Chordates
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Figure 17.5
SO…….
We are cousins with a
Starfish?
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Sperm
FERTILIZATION
MEIOSIS
Egg
MITOSIS
Zygote
(fertilized egg)
Eight-cell stage
Adult
METAMORPHOSIS
Blastula
(cross section)
Digestive tract
Outer cell layer
(ectoderm)
Larva
Inner cell layer
(endoderm)
Internal sac
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Early gastrula
(cross section)
Later gastrula Future middle
(cross section) layer of cells
(mesoderm)
Key
Haploid (n)
Diploid (2n)
Figure 17.2-8
21%
6%
14%
48%
11%
Living
Vertebrates
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VERTEBRATE EVOLUTION AND
DIVERSITY
• Vertebrates have unique endoskeletons composed of:
– A cranium (skull)
– A backbone made of a series of bones called vertebrae
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Characteristics of Chordates
• Chordates (phylum Chordata) all share four key features that
appear in the embryo and sometimes the adult:
– A dorsal, hollow nerve cord
– A notochord
– Pharyngeal slits
– A post-anal tail
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• Another chordate characteristic is body segmentation, apparent in
the:
– Backbone of vertebrates
– Segmental muscles of all chordates
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• Chordates consists of three groups of invertebrates:
– Lancelets are bladelike animals without a cranium.
– Tunicates, or sea squirts, also lack a cranium.
– Hagfishes are eel-like forms that have a cranium.
• All other chordates are vertebrates.
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Tunicates
Figure 17.28b
Mouth
Tail
Lancelet
Figure 17.28a
Ancestral
chordate
Chordates
Tunicates
Lancelets
Hagfishes
Vertebrates
Lampreys
Cartilaginous
fishes
Bony fishes
Mammals
Amniotes
Reptiles
Tetrapods
Amphibians
Figure 17.29
Fishes
• The first vertebrates were aquatic and probably evolved during
the early Cambrian period, about 542 million years ago. They:
– Lacked jaws
– Are represented today by hagfishes
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(a) Hagfish (inset: slime)
Figure 17.30a
• Lampreys:
– Are vertebrates
– Have a cranium
– But lack jaws
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(b) Lamprey (inset: mouth)
Figure 17.30b
Ancestral
chordate
Chordates
Tunicates
Lancelets
Hagfishes
Vertebrates
Lampreys
Cartilaginous
fishes
Bony fishes
Mammals
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Amniotes
Reptiles
Tetrapods
Amphibians
Figure 17.29
The two major groups of living fishes are the:
Cartilaginous fishes (sharks and rays) with a flexible
skeleton made of cartilage
Lateral line
(c) Shark, a cartilaginous fish
Figure 17.30c
And bony fishes with a skeleton reinforced by hard
calcium salts
Operculum
Lateral line
(d) Bony fish
Figure 17.30d
(a) Hagfish
(inset: slime)
(b) Lamprey
(inset: mouth)
Operculum
(c) Shark, a
cartilaginous fish
Lateral line
(d) Bony fish
Figure 17.30
• Cartilaginous and bony fishes have a lateral line system that
detects minor vibrations in the water.
• To provide lift off the bottom:
– Cartilaginous fish must swim but
– Bony fish have swim bladders, gas-filled sacs that make them buoyant
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Amphibians
• Amphibians:
– Exhibit a mixture of aquatic and terrestrial adaptations
– Usually need water to reproduce
– Typically undergo metamorphosis from an aquatic larva to a terrestrial
adult
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(a) Tadpole and adult golden palm tree frog
Red-eyed tree frog
Texas barred tiger salamander
(b) Frogs and salamanders: the two major groups of amphibians
Figure 17.31
• Amphibians:
– Were the first vertebrates to colonize land
– Descended from fishes that had lungs and fins with muscles
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Lobe-finned fish
Early amphibian
Figure 17.32
• Terrestrial vertebrates are collectively called tetrapods, which
means “four feet.”
• Tetrapods include:
– Amphibians
– Reptiles
– Mammals
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Reptiles
• Reptiles (including birds) and mammals are amniotes, which
produce amniotic eggs that consist of a fluid-filled shell inside of
which the embryo develops.
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• Reptiles include:
– Snakes
– Lizards
– Turtles
– Crocodiles
– Alligators
– Birds
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• Reptile adaptations to living on land include:
– Amniotic eggs
– Scaled, waterproof skin
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Dinosaur
Snake
Lizard
Crocodile
Birds
Turtle
Figure 17.33
• Nonbird reptiles are ectotherms, sometimes referred to as “coldblooded,” which means that they obtain their body heat from the
environment.
• A nonbird reptile can survive on less than 10% of the calories
required by a bird or mammal of equivalent size.
• Reptiles diversified extensively during the Mesozoic era.
• Dinosaurs were the largest animals ever to live on land.
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Birds
• Recent genetic evidence shows that birds evolved from a lineage
of small, two-legged dinosaurs during the great reptilian radiation
of the Mesozoic era.
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• Birds have many adaptations that make them lighter in flight:
– Honeycombed bones
– One instead of two ovaries
– A beak instead of teeth
• Unlike other reptiles, birds are endotherms, maintaining a
warmer and steady body temperature.
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Ancestral
chordate
Chordates
Tunicates
Lancelets
Hagfishes
Vertebrates
Lampreys
Cartilaginous
fishes
Bony fishes
Mammals
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Amniotes
Reptiles
Tetrapods
Amphibians
Figure 17.29
Mammals
• The first true mammals:
– Arose about 200 million years ago
– Were probably small, nocturnal insect-eaters
• Most mammals are terrestrial although dolphins, porpoises, and
whales are totally aquatic.
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• Mammalian hallmarks are:
– Hair
– Mammary glands that produce milk, which nourishes the young
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• There are three major groups of mammals:
– Monotremes, egg-laying mammals
– Marsupials, pouched mammals with a placenta
– And eutherians, placental mammals
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MAJOR GROUPS OF MAMMALS
Monotremes
(hatched from eggs)
Echidna adult
and egg
Marsupials
(embryonic at birth)
Eutherians
(fully developed at birth)
Kangaroo newborn and mother
Wildebeest newborn
and mother
Figure 17.35
• Eutherian placentas provide more intimate and long-lasting
association between the mother and her developing young than do
marsupial placentas.
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Lemurs, lorises,
and pottos
Ancestral
primate
Tarsiers
Apes
Gibbons
Anthropoids
Old World monkeys
Monkeys
New World monkeys
Orangutans
Gorillas
Chimpanzees
Humans
Figure 17.36
The Evolution of Primates
• Primates evolved from insect-eating mammals during the late
Cretaceous period.
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• Primates are distinguished by characteristics that were shaped by
the demands of living in trees. These characteristics include:
– Limber shoulder joints
– Eyes in front of the face
– Excellent eye-hand coordination
– Extensive parental care
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• Taxonomists divide the primates into three main groups.
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• The first group of primates includes:
– Lorises
– Pottos
– Lemurs
Tarsiers form the second group.
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• The third group, anthropoids, includes:
– Monkeys
– Hominoids, the ape relatives of humans
– And humans
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Ring-tailed
lemur
Tarsier
Black spider monkey
(New World monkey)
Patas monkey (Old World monkey)
Gorilla (ape)
Orangutan (ape)
Gibbon (ape)
Chimpanzee (ape)
Human
Figure 17.37
The Emergence of Humankind
• Humans and chimpanzees have shared a common African
ancestry for all but the last 5–7 million years.
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Some Common Misconceptions
• Chimpanzees and humans represent two divergent branches of the
anthropoid tree that each evolved from a common, less
specialized ancestor.
• Our ancestors were not chimpanzees or any other modern apes.
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• Human evolution is not a ladder with a parade of fossil hominids
(members of the human family) leading directly to modern
humans.
• Instead, human evolution is more like a multibranched bush than
a ladder.
• At times in hominid history, several different human species
coexisted.
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0
?
Homo
Homo
neanderthalensis sapiens
Paranthropus
boisei
0.5
1.0
1.5
Millions of years ago
2.0
2.5
Homo erectus
Paranthropus
robustus
3.0
3.5
Homo
habilis
Australopithecus
africanus
4.0
4.5
5.0
5.5
Australopithecus
afarensis
6.0 Ardipithecus
ramidus
Figure 17.38
• Upright posture and an enlarged brain appeared at separate times
during human evolution.
• Different human features evolved at different rates.
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Australopithecus and the Antiquity of Bipedalism
• Before there was the genus Homo, several hominid species of the
genus Australopithecus walked the African savanna.
• Fossil evidence pushes bipedalism in A. afarensis back to at least
4 million years ago.
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(a) Australopithecus (b) Ancient footprints
afarensis skeleton
(c) Model of an
Australopithecus
afarensis male
Figure 17.39
Homo Habilis and the Evolution of Inventive Minds
• Homo habilis, “handy-man”:
– Had a larger brain, intermediate in size between Australopithecus and
modern humans
– Walked upright
– Made stone tools that enhanced hunting, gathering, and scavenging on the
African savanna
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Homo Erectus and the Global Dispersal of Humanity
• Homo erectus was the first species to extend humanity’s range
from Africa to other continents.
• The global dispersal began about 1.8 million years ago.
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• Homo erectus:
– Was taller than H. habilis
– Had a larger brain
– Gave rise to Neanderthals
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The Origin and Dispersal of Homo Sapiens
• The oldest known fossils of our own species, Homo sapiens:
– Were discovered in Ethiopia
– Date from 160,000 to 195,000 years ago
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• DNA studies strongly suggest that all living humans can trace
their ancestry back to a single African Homo sapiens woman who
lived 160,000 to 200,000 years ago.
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• Fossil evidence suggests that our species emerged from Africa in
one or more waves.
• The oldest fossils of H. sapiens outside of Africa are 50,000 years
old.
• The oldest fossils of humans in the New World are uncertain, but
are at least 15,000 years old.
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• The global consequences of human evolution have been
enormous. Humans can:
– Defy our physical limitation
– Shortcut biological evolution
– Change the environment to meet our needs
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Figure 17.42