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Chapter 27: Evolution
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Evolution of Small Organic
Molecules
• Experiments by Stanley Miller in 1953
tested the hypothesis that small organic
molecules were formed at the ocean’s
surface.
• The first atmospheric gases (methane,
ammonia, and hydrogen) were placed into
a closed system, heated, and circulated
past an electric spark to simulate lightning.
• A variety of amino acids and organic acids
formed.
Miller’s experiment
Macromolecules
• There are three hypotheses concerning
how small organic molecules could give
rise to macromolecules:
• The RNA-first hypothesis.
• The Protein –first hypothosis.
• The Clay theory RNA and Protein arose
together
The Protocell
• Before the first true cell, there would have
been a protocell that had a lipid-protein
membrane and used energy metabolism.
• Fox has shown that if lipids are available to
microspheres, the two form a lipid-protein
membrane.
• Other work by Alexandr Oparin has shown
that concentrated mixtures of
macromolecules form coacervate droplets
that a semipermeable boundary may form
around.
The True Cell
• A true cell is a membrane-bounded
structure that can carry on protein
synthesis to produce the enzymes that
allow DNA to replicate.
• It is possible that the sequence of DNA to
RNA to protein developed in stages.
• Once the protocells acquired genes that
could replicate, they became cells capable
of reproducing, and evolution began.
Microevolution
Five Agents of Evolutionary Change
• Mutations provide new alleles and therefore underlie
all other mechanisms that produce variation.
• Genetic Drift changes in gene pool by chance due to
fouder effect or bottleneck effect
• Gene Flow is the movement of alleles between
populations (via migration)
• Nonrandom Mating, when individuals pair up, not by
chance, but by genotype or phenotype.
• Natural Selection, where populations become adapted
to their environment (specialized)
Natural Selection
• Natural selection is the process by which populations
become adapted to their environment.
• Evolution by natural selection requires:
• Variation
• Inheritance of the genetic difference
• Differential adaptedness
• Differential reproduction.
• Three types of natural selection are known:
• Stabilizing selection – an intermediate
phenotype is favored.
• Directional selection – one extreme phenotype
is favored.
• Disruptive selection – both extreme phenotypes
are favored over an intermediate phenotype.
Chapter 30: Animals: Part I
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction o display.
Evolution and Classification of
Animals
• Animals are multicellular heterotrophs that
ingest their food.
• Animals belong to the Eukarya and kingdom
Animalia.
• In general, animals have some form of
locomotion and have tissues and organs.
• The adult is typically diploid and practices
sexual reproduction.
• An embryonic stage undergoes
development.
Evolution of Animals
• It is difficult to trace the complete
evolutionary tree of animals because softbodied animals are poorly preserved as
fossils.
• All animals probably evolved from a
protistan ancestor.
• All the major animal phyla include some
invertebrates, animals without backbones.
• The phylum Chordata is mainly composed
of vertebrates.
Animal diversity
Criteria for Classification
• The classification of animals is based on
the level of organization or number of
germ layers, symmetry, type of coelom,
body plan, and presence or absence of
segmentation.
• An evolutionary tree based on these
features depicts a possible evolutionary
relationship between the animals.
Evolutionary tree
Evolutionary tree
Invertebrates
Characterizing Animals
•
•
•
•
Level of Organization
Type of Body Plan
Type of Symmetry
Type of Coelom
Level of Organization
• Animals can have the cellular level, the
tissue level, or the organ level of
organization.
• One of the main events during animal
development is the establishment of germ
layers.
• If two germ layers (ectoderm and
endoderm) are present, then the animal
has the tissue level of organization; if all
three germ layers are present, the organ
level of organization is attained.
LOOK! These
Are “germ layers”
that are the basis
Of STEM-CELLS!
•
•
•
•
Type of Body Plan
Two body plans are present in the animal
kingdom: the sac plan and tube-within-atube plan.
Animals with a sac plan have an
incomplete digestive system with only one
opening.
Animals with the tube-within-a-tube plan
have a complete digestive system.
Two openings allows for specialization
along the length of the tube.
Type of Symmetry
• Animals can be asymmetrical, radially
symmetrical, or bilaterally symmetrical.
• Asymmetrical animals have no particular
symmetry.
• Radial symmetry means the animal is
organized similar to a wheel.
• Bilateral symmetry means the animal has
definite right and left halves.
• Bilateral symmetry leads to cephalization.
• Type of Coelom
• A true coelom (in coelomates) is an internal
body cavity completely lined with
mesoderm, where internal organs are
found.
• Coelomates are either protostomes or
deuterostomes.
• Acoelomates have mesoderm but no body
cavity.
• Animals that have a pseudocoelom have a
body cavity incompletely lined with
mesoderm.
Introducing the Invertebrates
• Sponges are asymmetrical.
• Cnidarians have radial symmetry.
• All other phyla contain bilaterally symmetrical
animals.
• Flatworms have three germ layers but no coelom.
• Roundworms have a pseudocoelom and a tubewithin-a-tube body plan.
Kingdom Animalia
Sub-Kingdom Metazoa
Sub-Kingdom Parazoa
Phyllum Cnidera
Phyllum Porifera
Phyllum Platyhelminths
(jellyfish, hydra, sea anenomae)
(flukes, tapeworm, planeria)
(sponges)
Phyllum Aschelminths
Phyllum Mollusca
(rotifers and nemotes: ascaris)
(snail, clams, octopi)
Phyllum Annelida
(segmented worms)
Phyllum Arthopods
Phyllum Echinodermata
(insects, lobsters, spiders)
(starfish, sea urchins)
Phyllum Chordata
(early and late vertebrates)
Sponges: Phyllus Porifera
• Sponges are mainly marine animals at the
cellular level of organization.
• The sponge body wall has an outer layer
of epidermal cells; a middle layer
consisting of semi-fluid matrix where
amoeboid cells transport nutrients,
produce spicules, and form sex cells; and
an inner layer of collar cells with flagella
that wave water through pores and out an
osculum.
Sponge
Kingdom Animalia
Sub-Kingdom Metazoa
Sub-Kingdom Parazoa
Phyllum Cnidera
Phyllum Porifera
Phyllum Platyhelminths
(jellyfish, hydra, sea anenomae)
(flukes, tapeworm, planeria)
(sponges)
Phyllum Aschelminths
Phyllum Mollusca
(rotifers and nemotes: ascaris)
(snail, clams, octopi)
Phyllum Annelida
(segmented worms)
Phyllum Arthopods
Phyllum Echinodermata
(insects, lobsters, spiders)
(starfish, sea urchins)
Phyllum Chordata
(early and late vertebrates)
Phyllum: Cnidara
• Cnidarians are mostly coastal marine
animals with a tissue level of organization
and radial symmetry.
• They may be a polyp or a medusa or may
alternate between the two forms.
• They have cnidocytes that discharge stinging
nematocysts, long threads that may have
spines and contain a poison.
• Cnidarians are diverse and include sea
anemones, coral, and jellyfishes.
Hydra
• A hydra polyp has an outer layer of
epidermis derived from ectoderm and an
inner layer called gastrodermis derived from
endoderm.
• Mesoglea lies between the two layers and
contains a nerve net that communicates with
muscle fibers so that the animal is able to
move.
• Digestion begins in a gastrovascular cavity
and finishes in gastrodermal cells.
• Nutrients and gases are distributed from
layer to layer by diffusion.
Anatomy of Hydra
Kingdom Animalia
Sub-Kingdom Metazoa
Sub-Kingdom Parazoa
Phyllum Cnidera
Phyllum Porifera
Phyllum Platyhelminths
(jellyfish, hydra, sea anenomae)
(flukes, tapeworm, planeria)
(sponges)
Phyllum Aschelminths
Phyllum Mollusca
(rotifers and nemotes: ascaris)
(snail, clams, octopi)
Phyllum Annelida
(segmented worms)
Phyllum Arthopods
Phyllum Echinodermata
(insects, lobsters, spiders)
(starfish, sea urchins)
Phyllum Chordata
(early and late vertebrates)
Flatworms
• Flatworms are characterized by the tissue
level of organization and a sac body plan.
• These acoelomates have three germ
layers, and have all organs except
respiratory and circulatory organs.
• The flat body facilitates diffusion of oxygen
and other molecules from cell to cell.
Planarian
Schistosomiasis
Kingdom Animalia
Sub-Kingdom Metazoa
Sub-Kingdom Parazoa
Phyllum Cnidera
Phyllum Porifera
Phyllum Platyhelminths
(jellyfish, hydra, sea anenomae)
(flukes, tapeworm, planeria)
(sponges)
Phyllum Aschelminths
Phyllum Mollusca
(rotifers and nemotes: ascaris)
(snail, clams, octopi)
Phyllum Annelida
(segmented worms)
Phyllum Arthopods
Phyllum Echinodermata
(insects, lobsters, spiders)
(starfish, sea urchins)
Phyllum Chordata
(early and late vertebrates)
Roundworms
• Roundworms have the tube-within-a-tube plan;
they are prevalent in soil and some parasitize
animals and plants.
• The pseudocoelom is a body cavity
incompletely lined with mesoderm.
• The fluid-filled interior forms a hydrostatic
skeleton.
• Most species of roundworms have separate
males and females.
Coelom structure and function
Roundworm anatomy
Kingdom Animalia
Sub-Kingdom Metazoa
Sub-Kingdom Parazoa
Phyllum Cnidera
Phyllum Porifera
Phyllum Platyhelminths
(jellyfish, hydra, sea anenomae)
(flukes, tapeworm, planeria)
(sponges)
Phyllum Aschelminths
Phyllum Mollusca
(rotifers and nemotes: ascaris)
(snail, clams, octopi)
Phyllum Annelida
(segmented worms)
Phyllum Arthopods
Phyllum Echinodermata
(insects, lobsters, spiders)
(starfish, sea urchins)
Phyllum Chordata
(early and late vertebrates)
Molluscs
• Molluscs, along with annelids and
arthropods, are protostomes because the
first embryonic opening becomes the
mouth.
• Because the true coelom form by the
splitting of the mesoderm, protostomes are
also schizocoelomates.
• Many protostomes also have trochophore
(top-shaped) larvae.
Molluscan diversity
Kingdom Animalia
Sub-Kingdom Metazoa
Sub-Kingdom Parazoa
Phyllum Cnidera
Phyllum Porifera
Phyllum Platyhelminths
(jellyfish, hydra, sea anenomae)
(flukes, tapeworm, planeria)
(sponges)
Phyllum Aschelminths
Phyllum Mollusca
(rotifers and nemotes: ascaris)
(snail, clams, octopi)
Phyllum Annelida
(segmented worms)
Phyllum Arthopods
Phyllum Echinodermata
(insects, lobsters, spiders)
(starfish, sea urchins)
Phyllum Chordata
(early and late vertebrates)
Annelids
• Annelids are segmented both externally,
and internally by partitions called septa.
• Annelids have a hydrostatic skeleton, and
partitioning of the coelom permits each
body segment to move independently.
• The tube-within-a-tube body plan allows the
digestive tract to have specialized organs.
Polychaete diversity
Earthworm, Lumbricus
Leeches
• Most leeches are fluid feeders that attach
themselves to open wounds using
suckers.
• Bloodsuckers, such as the medicinal
leech, can cut through tissue.
• An anticoagulant (hirudin) in their saliva
keeps blood from clotting.
Kingdom Animalia
Sub-Kingdom Metazoa
Sub-Kingdom Parazoa
Phyllum Cnidera
Phyllum Porifera
Phyllum Platyhelminths
(jellyfish, hydra, sea anenomae)
(flukes, tapeworm, planeria)
(sponges)
Phyllum Aschelminths
Phyllum Mollusca
(rotifers and nemotes: ascaris)
(snail, clams, octopi)
Phyllum Annelida
(segmented worms)
Phyllum Arthopods
Phyllum Echinodermata
(insects, lobsters, spiders)
(starfish, sea urchins)
Phyllum Chordata
(early and late vertebrates)
Arthropods
• Arthropods are the most varied and
numerous of animals.
• The success of arthropods is largely
attributable to a flexible exoskeleton, jointed
appendages, and specialization of body
regions.
• Three body regions – head, thorax, and
abdomen – with specialized appendages in
each region, and a well-developed nervous
system characterize this group.
Arthropod diversity
Insect diversity
Arachnid diversity
Chapter 31: Animals: Part II
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Kingdom Animalia
Sub-Kingdom Metazoa
Sub-Kingdom Parazoa
Phyllum Cnidera
Phyllum Porifera
Phyllum Platyhelminths
(jellyfish, hydra, sea anenomae)
(flukes, tapeworm, planeria)
(sponges)
Phyllum Aschelminths
Phyllum Mollusca
(rotifers and nemotes: ascaris)
(snail, clams, octopi)
Phyllum Annelida
(segmented worms)
Phyllum Arthopods
Phyllum Echinodermata
(insects, lobsters, spiders)
(starfish, sea urchins)
Phyllum Chordata
(early and late vertebrates)
Echinoderms
• Echinoderms and chordates are deuterostomes.
• In deuterostomes, the second embryonic opening
becomes the mouth and a coelom forms by
outpocketing of the primitive gut making these
animals enterocoelomates.
• A dipleurula larva is found among some.
Protostomes versus deuterostomes
Evolutionary tree
Invertebrates
Characteristics of Echinoderms
• Echinoderms are a diverse group of
marine animals; there are no terrestrial
echinoderms.
• They have an endoskeleton consisting of
spine-bearing, calcium-rich plates.
• Echinoderms are often radially
symmetrical, although the larva is a freeswimming filter feeder with bilateral
symmetry.
• Echinoderm Diversity
• Echinoderms include:
• Sea lilies (class Crinoidea)
• Sea cucumbers (class Holothuroidea)
• Brittle stars (class Ophiuroidea)
• Sea urchins and sand dollars (class
Echinoidea)
• Sea stars (class Asteroidea)
Echinoderm diversity
Sea star anatomy and behavior
Kingdom Animalia
Sub-Kingdom Metazoa
Sub-Kingdom Parazoa
Phyllum Cnidera
Phyllum Porifera
Phyllum Platyhelminths
(jellyfish, hydra, sea anenomae)
(flukes, tapeworm, planeria)
(sponges)
Phyllum Aschelminths
Phyllum Mollusca
(rotifers and nemotes: ascaris)
(snail, clams, octopi)
Phyllum Annelida
(segmented worms)
Phyllum Arthopods
Phyllum Echinodermata
(insects, lobsters, spiders)
(starfish, sea urchins)
Phyllum Chordata
(early and late vertebrates)
Chordates
• Chordates (tunicates, lancelets, and
vertebrates) have:
• a supporting notochord,
• a dorsal hollow nerve cord,
• pharyngeal pouches, and a
• post-anal tail at one time during their
development.
Chordate characteristics
Evolution of Chordates
• The lancelets and tunicates are
invertebrate chordates.
• Vertebrates include the fishes, amphibians,
reptiles, birds, and mammals.
• Cartilaginous fishes were the first to have
jaws; amphibians evolved legs and invaded
land.
• Reptiles, birds, and mammals have means
of reproduction suitable to land.
Evolutionary tree of chordates
No way!
Invertebrate Chordates
• Lancelets and tunicates are the invertebrate
chordates.
• Lancelets are small animals found in shallow
water along the coasts; they filter feed on
microscopic organisms.
• Tunicates (sea squirts) live on the ocean floor
and filter water entering the animal through an
incurrent siphon.
• Adult tunicates lack chordate characteristics
except gill slits, but adult lancelets retain the
four chordate characteristics.
Habitat and anatomy of a lancelet,
Brachiostoma
Anatomy of a tunicate, Halocynthia
True Vertebrates
• At some time during their lives, all vertebrates
have the four chordate characteristics.
• The notochord is replaced by the vertebral
column; this endoskeleton demonstrates
segmentation.
• The internal organs are well developed and
cephalization places complex sense organs at
the head.
• Vertebrates are distinguished in particular
by these features:
• Living endoskeleton
• Closed circulatory system
• Paired appendages
• Efficient respiration and excretion
• High degree of cephalization
• The evolution of jaws allowed some
vertebrates to take up the predatory way
of life.
Milestones in vertebrate evolution
We got bones!
We made it on land!
We laid land-eggs!
The first vertibrate animals to arrive:
Fishes!
• Today there are three living classes of fishes:
jawless fishes, cartilaginous fishes, and bony
fishes – the last two groups have jaws.
• Jawless Fishes
• The first vertebrates were jawless fishes, today
represented by hagfishes and lampreys with no
scales or paired fins. (these fish suck the blood of other
fishes…like underwater vampires)
• Water moves in and out through gill openings.
The most primitive jawed fishes:
Cartilaginous Fishes
• The cartilaginous fishes include the sharks, rays and
skates which have skeletons made of cartilage (like our
ears and nose…strong, but still soft and flexible).
• Skates and rays are flat fishes that live partly buried in
the sand and feed on mussels and clams –”everybody do
the stingray shuffle!”
• Sharks and rays have a sense of electric currents in
water, a lateral line system, and a keen sense of smell;
these attributes help detect prey – they can feel you even
when they can’t see you! So don’t thrash!!!!
• Bony Fishes
• Bony fishes have jaws and two pairs of fins and
are the most diverse and numerous of all
vertebrates (think: tuna, salmon, koi, etc...)
• Bony fishes include those that are ray-finned
(most abundant) and a few that are lobefinned; some of the lobed-finned fishes have
lungs and likely gave rise to amphibians.
• A swim bladder may provide buoyancy in rayfinned fishes.
Jawed fishes
Please don’t step on me!
Amphibians
• Amphibians evolved from the lobe-finned
fishes and are tetrapods with two pairs of limbs.
• They are represented today by frogs, newts,
toads, and salamanders.
• Amphibians usually return to the water to
reproduce and require moist habitats.
• Frog tadpoles metamorphose into terrestrial
adults with lungs.
Frog metamorphosis
• These features distinguish amphibians:
• Usually tetrapods
• Mostly metamorphosis
• Three-chambered heart (2 atria, one
ventricle)
• Usually lungs in adults
• Smooth, moist skin
Reptiles
• Reptiles include the extinct dinosaurs and
today’s snakes, lizards, turtles, alligators, and
crocodiles.
• Reptiles have well-developed lungs within a rib
cage; they are covered with scales that protect
them from desiccation and predators.
• Reptiles have internal fertilization and also lay a
shelled egg, which contains extraembryonic
membranes, including an amnion that allows
the embryo to develop on land.
The tongue as a sense organ
The reptilian egg allows
reproduction on land
• Features that distinguish reptiles include:
• Usually tetrapods
• Lungs with expandable rib cages
• Shelled, leathery egg
• Dry, scaly skin
• Fishes, amphibians, and reptiles are “ectothermic”also known as….. COLD-BLOODED!
• Therefore…reptiles try to regulate their body
temperature by moving to a warmer or cooler location
as needed.
• The opposite of this is WARM-BLOODED, or
“endothermic” b/c we regulate body temp. from our
insides!
Look up! Beautiful Birds
• Birds are characterized by the presence of
feathers, which are modified reptilian scales.
• Birds lay hard-shelled eggs rather than the
leathery eggs of reptiles.
• Birds are likely closely related to bipedal
dinosaurs, although this is still under study.
Bird anatomy
• Anatomy and Physiology of Birds
• Features of birds are related to the ability to
fly.
• Bird forelimbs are modified as wings.
• Bones are hollow (yes way!) and laced with
air cavities; the sternum has a keel to which
flight muscles attach. (weigh a bird, VERY light!)
• A horny beak replaces teeth.
• Respiration is efficient due to air sacs.
• Birds have a four-chambered heart, and birds
are homeothermic.
Bird beaks
Bird circulatory system
• Classification of Birds
• The classification of birds is based on beak
and foot types and to some extent on
habitat and behavior.
• These features distinguish birds:
• Feathers
• Hard-shelled egg
• Four-chambered heart
• Usually wings for flying
• Air sacs
• Homeothermic
Mammals
• Mammals evolved from reptiles and
flourished after the demise of dinosaurs.
• Mammals have hair that helps them
maintain a constant body temperature.
• Like birds, mammals have a fourchambered heart.
• Internal development in the uterus shelters
the young.
• Mammary glands allow mammals to
nourish their young.
Dr. L Humphries
lhumphries@elcamino.edu
Spring 2005: Fundamentals of Biology
Section 1107
Biology 10
4-Units
Lab Ex: 16 histology
Loose fibrous connective tissue
Adipose tissue
Hyaline cartilage
Compact bone
Skeletal muscle
Smooth muscle
Cardiac muscle
Nail anatomy
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