CHAPTER 20

Phylogeny

phylogeny – evolutionary history of a species or group of species

systematics – classifying organisms & determining their evolutionary relationships

Pattern of Evolution

taxonomy – how organisms are named & classified

Binomial Nomenclature

Carolus Linnaeus (18th century) – Genus &

species

Dashing King Philip Came Over For Great spaghetti.

Con. 20.1

Phylogenetic tree may not match classification. Why not?

Phylogenetics is about evolutionary relationships (descent not phenotypes)

*branch points

*sister taxa

*polytomy (more than 2 descendant groups) – usually means something is in question

Morphological Homology

-similar # & arrangement of structure (mammals & humerus bone)

-analogous structures: same function (bats & birds fly)

Molecular Homology vs. Analogy

-# of DNA sequences that match

-same function of DNA sequences

- Homoplasies vs Homology

Con. 20.2

Cladistics (common ancestry)

Clade – groups that include the ancestral species & all of its descendants (also called a monophyletic group)

Paraphyletic – contains the ancestral species & some but not all of the descendants

Polyphyletic – 2 or more common ancestors & some of their descendants

Con. 20.3 p. 387

shared ancestral character – a characteristic that originated w/the ancestor

shared derived character – a characteristic only found in that clade

outgroup – a species or group that diverged before the ancestral characteristic

ingroup – group of study p. 388 fig. 20.11

Proportional Branch Lengths show amount of change in proportion to time.

What to do with so much DNA?!

Maximum Parsimony – simplest explanation (get rid of what you don’t need)

Maximum Likelihood – most likely sequence of evolutionary events (logical)

NOTE: Any phylogenetic tree is constantly changing with the influx of DNA data.

Molecular Clock

-each gene has its own clock

-absolute time of evolutionary change

-reliable average rate of evolution based on nucleotide, codon, aa differences

Con. 20.4

-same gene may evolve at a different rate in other organisms

Neutral Theory: if most of the proteins & genes don’t pertain to fitness then their clock should be regular like a clock

Debate

1.irregularities can be from natural selection

2.neutral genetic variation can also lead to diversity

3.beyond fossil record leads to assumptions

Horizontal Gene Transfers

- genes transferred from one genome to another by transposable elements, plasmids, viral, etc.

- can’t really determine when some organisms diverged

- What about protists?!

I can’t take the indecision!!

CHAPTER 27

The Rise Animal Diversity

What Makes it an Animal?

1. Must ingest & use enzymes inside body

2. Plasma Membrane – no wall

3. Most move at some time in their life span

4. Sexual reproduction

5. Hox genes (development of embryos)

When Did Animals Arrive?

Neoproterozoic Era

•565-550 millions years ago

•Ediacaran biota: multicellular eukaryotes (sponges, cnidarians)

Paleozoic Era

•542-251 million years ago

•Cambrian explosion

•First arthropods, chordates, echinoderms

•Predators have better equipment

•Adaptation to land

Mesozoic Era

•251-65.5 million years ago

•No groups but evolution occurred due to new habitats

•Dinosaurs, first mammals, flight

Cenozoic Era

•65.5 million years ago to present

•Mass extinctions of both terrestrial & marine animals

•Rise of the mammals

•Humans

BODY SYMMETRY 1) Asymmetrical: no pattern 2) Radial symmetry: parts are organized in

a circle around an axis

3) Bilateral symmetry– 2 halves on either side of a central plane anterior – toward head or front posterior – toward tail or back dorsal – top ventral – abdomen or bottom

• animals tend to exhibit cephalization

3 Tissue Layers: -ectoderm: outer layer & will become the epidermis & nervous system -mesoderm: middle layer & will become most of the organs & tissues -endoderm: inner layer & will become the innermost lining of our digestive tract (archenteron)

diploblastic – 2 germ layers triploblastic – all 3 germ layers

Body Cavities

coelom – fluid or air-filled space

coelomates – suspend organs (mesoderm)

pseudocoelomates – not quite false (mesoderm & endoderm)

acoelomates - solid

Protostome & Deuterostome Development

• Spiral cleavage

• Determinate cleavage

• Coelom from splits in mesoderm

• Mouth forms from blastopore

• Radial cleavage

• Indeterminate cleavage

• Coelom from mesodermal outpocketings of archenteron

• Mouth forms from secondary opening

PHYLUM PORIFERA = Sponges

• Least complex animals

• Simple body plans

• No true body tissues,

organs, or systems

Sessile: do not move

Obtaining Food • Food is filtered out of the water =

suspension feeding

• Choanocytes (collar cells) pull the water thru the ostia

• They have flagella that help move water thru bringing in O2 & carrying away wastes (leaves via osculum)

• Nutrients are distributed thru the body by amoebocytes

• Compound cribrostatin kills penicillin-

resistant Streptococcus

• The body is supported by a skeleton made

of spongin (flexible protein fibers),

spicules (calcium carbonate particles), or

both

osculum

PHYLUM CNIDARIA

• Diploblastic, radial

• More complex than

sponges

• Have tissues and few simple organs

• Most live individually except

for coral & hydra

• Most live in salt water except for hydra

2 Body Forms

Polyp: vase shaped

• Sessile

• Mouth up

• Hydra, sea anemone

Medusa: bell shaped

• Free swimming

• Mouth down

• Jellyfish (Portuguese Man-of-War)

Feeding & Defense

• Arm-like tentacles surround mouth

• tentacles contain stinging cells

(cnidocytes) used to capture food &

to protect

• When stimulated, its nematocyst

(poisoned barbed harpoon) can

paralyze or ensnare prey

• Have a nerve net = web of

interconnected nerve cells

• This allows simple

responses & movement

PHYLUM CTENOPHORA

(comb jellies)

• move thru water by beating their 8 rows of cilia

• capture prey w/ sticky substance secreted by colloblasts

• The apical organ enables them to sense their orientation in the water

• Most are hermaphroditic

• Many have bioluminescence

Comb

Jellies

PHYLUM PLATYHELMINTHES

• Flatworms

• bilateral symmetry

• Exhibit cephalization

• Triploblastic

• Acoelomates

• Protonephridia – tubules w/ciliated cells,

pull fluid through

Planarian Neural Control

• more complex than nerve net of

cnidarians

cerebral ganglia: serves as simple brain

• sense light w/ eyespots

Tapeworms

• can live in the intestines of almost all vertebrates

• surrounded by tegument

• Attach to the host w/ scolex (hooks and suckers)

Tapeworm

Structure • NO light-sensing

organs, mouth,

gastrovascular

cavity, and

digestive organs

• Produces new

body segments

(proglottids)

behind head

(may exceed 10

m long)

Each segment has both male & female organs

• eggs are fertilized in segment • segment breaks off & leaves host’s body

PHYLUM ROTIFERS

• tiny

• fresh, marine, damp soil

• alimentary canal – digestive tube

w/separate mouth & anus

• pseudocoelom (serves as hydrostatic

skeleton)

• crown of cilia

Reproduction:

Parthenogenesis – but

only females or both

but males survive only

to fertilize eggs

Phylum ECTOPROCTS & BRACHIOPODS

• Lophophore: crown of ciliated

tentacles surrounding the mouth

• U-shaped alimentary canal

• Pseudocoelom

Ectoprocts:

• colony encased

in exoskeleton

• common name is

bryozoans

Brachiopods:

• look like bivalves

• all marine

• attached to sea

floor by a stalk

PHYLUM NEMATODA

• roundworms

• largest phylum of worms

• slender, tapered at both ends

• alimentary canal

• pseudocoelom

• longitudinal body wall muscles

• 2 body openings (mouth & anus)

• covered by a protective cuticle

• Most species are free-living;

some parasites

• separate sexes

Types of Roundworms

A) Ascaris - infects pigs, horses, and

humans.

B) Hookworms - intestinal parasites

that feed on blood

C) Trichinella - infects humans, other

mammals

D) Pinworms- common human

parasites (do not cause serious

diseases)

Phylum MOLLUSCA

• “soft bodies”

• clams, snails, slugs, squids, octopuses

• Bilaterally symmetric invertebrates

• Some have a calcium carbonate shell

• coelomates

• Most aquatic mollusks and

annelids have a larval stage =

trochophore

Cilia

mouth

anus

Mollusk Body Plan

visceral mass: contains body organs

head-foot:

Head- mouth, sensory structures

Foot- large, muscular organ for locomotion

mantle: layer of epidermis that covers visceral mass

• secretes the shell or protects the body if lacking a shell

• Mantle cavity: houses gills

• nervous system consists of paired

clusters of nerve cells = ganglia

Other Gastropods

PHYLUM ANNELIDA

- “little rings”

• bilaterally symmetrical, segmented worms

• coelomates, divided into separate compartments by partitions

• have external bristles (setae) and some have fleshy protrusions (parapodia)

Phylum ARTHROPODA

• Largest animal phylum

• “jointed legs”

• Have body segments w/ appendages

• high degree of cephalization (antennae

and compound eyes

• open circulatory system

Body regions- • head, thorax, and abdomen • 2 or 3 can be fused together

•Body Cavity &

digestive system

possess mouth &

anus

•Nervous system

is similar to

annelids, but w/

larger brains

Skeletal Structure

• Have an exoskeleton

• Made of protein & carbohydrate = chitin

• Sheds exoskeleton as it grows = molting

1) Animal splits old, tight exoskeleton

2) Crawls out 3) Puffs up w/ air or water 4) Secretes new exoskeleton (very vulnerable)

PHYLUM ECHINODERMATA

• “ spiny-skinned”

–Sessile or motile

–pentaradial symmetry

–endoskeleton

–water-vascular system

–tube feet

Structure

• Endoskeleton of calcium carbonate plates (ossicles) supports and protects the body

(1st animals w/ endoskeleton)

• NO circulatory, excretory, or respiratory organ systems

• Nervous system- nerve ring and radial nerve that runs along each arm

Water Vascular System

• Network of water filled canals

• Tube feet act like suction cups for moving & feeding

Parts:

Madreporite- opening on top

Ring canal- center circle

Radial canals- go from ring canal

into each arm/ray

Ampulla- like “bulb” of an

eyedropper

Tube feet- apply suction to a surface

Characteristics of all Chordates

• Notochord – flexible rod-like structure on dorsal side of animal; site of what will be the spine

• Dorsal hollow nerve cord – dorsal bundle of nerves (spinal cord)

• Pharyngeal slits – paired openings in throat behind mouth; turn into gills in fish; fuse to form pharynx & ear canals in human

• Muscular, post-anal tail – muscle attachment w/skeleton

Subphylum Cephalochordata

• lancelets

• Retain notochord, dorsal nerve cord,

pharyngeal pouches, and postanal tail

thruout life

• feed by filtering water thru slits in

pharynx

• Invertebrate chordates

Subphylum Urochordata

• tunicates or sea

squirts

• Most are sessile

as adults

• barrel-shaped filter

feeders

• hermaphrodites

* There are 3 separate classes of fish with over 30,000 species!—Account for more than half of all living vertebrates.

Class Agnatha

Class Chondrichthyes

Class Osteichthyes

Class Agnatha (Jawless Fish) Lamprey, hagfish

• Both have round mouths, long tube-like bodies covered w/slimy skin

• Neither have scales or paired fins

• Skeleton is made of cartilage which is tough & flexible

• Hagfish lives in saltwater (a scavenger)

• Lamprey lives in both salt & freshwater

It attaches by suction, cut into fish, then

feed on blood & body fluids (parasite)

Class Chondrichthyes

• Cartilaginous fish: sharks, skates, rays

• Skeletons of cartilage covered with thin layer of CaCO3

• Moveable jaws

• Scales resemble teeth; skin feels like sandpaper

Class Osteichthyes

• Bony fish: bass, blue gill, zebra, etc.

1)Operculum – bony flap that helps protect gills & helps pull water through for breathing by opening & closing—also helps in communication,

(flared gills show aggression in some

species)

2)Heavy bony skeleton is strong and allows for attachment and use of powerful muscles. Ossification is the complete replacement of cartilage by bone.

3)Lateral Line System •is a special sensory system extending on both sides along its length •Water movement causes nerves to send messages to the brain •can detect motionless objects by the movement of water that objects reflect

3 Kinds of Bony Fish 1)Lobe-finned fish - fins are lobe-like &

fleshy; thought to be extinct until 1938 when one was netted in South Africa

- Coelacanth: brackish waters 60 caught

-different from ray-finned fish in that its

fins have several large bones with

muscles attached, are large and fleshy,

and in many cases are jointed

2)Lungfish - has both gills & lungs which allows them to live in shallow waters that dry up during summer & burrow in mud when water dries up; found in S. America, Australia, Africa

3)Ray-finned fish - fins are made of long thin bones covered w/skin; bass, catfish, blue gill, swordfish, parrotfish (most bony fish)

-They have an internal skeleton of parallel bony rays that stiffen and support each fin.

Buoyancy - swim bladder (air sac) allows the fish to adjust its density so it can rise or sink without swimming

- transfer of gases (mostly oxygen) between swim bladder & blood varies

- deep sea fish often have oil in their swim bladders - some bottom dwellers don’t have swim bladders

Swim bladder

Tetrapods

• Amphibian means “double life” (they spend time on land & in water)

• ectotherms

• smooth, moist skin that oxygen & carbon dioxide exchanges through (gas exchange also occurs through lining of mouth)

• small sac-like lungs for breathing

Amphibian Metamorphosis

• The change a larva undergoes in order to become an adult

• rate at which it grows & the length of time they spend as a larvae depends on the species, water temp. & food

• changes occur in their bodies & in food supply (yolk, herbivore, carnivore)

CHARACTERISTICS,…

1)Live in water and on land—eggs are usually laid in water and fertilized externally, larva live in water, and adults live on land. 2)Gills and Lungs—Larva have gills, but by adulthood, most gills are replaced by lungs

3)Cutaneous Respiration—Frogs, salamanders, and caecilians supplement their lungs by absorbing oxygen through their moist skin 4)Pulmonary veins—After the blood is pumped through the lungs, two large veins return the oxygenated blood to the heart to be pumped to the rest of the body. (Allows for greater blood pressure)

5)Three chambered heart—A partially divided heart where the ventricle (chamber pumping blood from the heart) contains a mixture of oxygenated and deoxygenated blood which is delivered to the amphibian’s tissues.

Three orders: Anura (without tail) = frogs and toads Urodela (visible tail) = salamanders and newts Apoda (without foot) = caecilians (worm-like and nearly blind)

--Most anurans return to water to reproduce --Eggs are laid directly in water and fertilized externally --Tadpole (larva) hatches and lives in water (most as herbivores) --After considerable growth, tadpoles change into adults by a process called metamorphosis.

Reptiles & Birds

Characteristics of Reptiles

• Ectotherm

• thick, dry, scaly, waterproof skin (prevents animal from drying out or injury)

• 4 legs w/claws (claws used for digging, climbing, running)

• vary in size, shape, color

• live on every continent except Antarctica

•Live in every ocean except the polar regions

•breathe w/lungs

•3 chambered heart (lower chamber partially divided to keep oxygen rich blood from blood of the body)

Mmmm!!!

Development of the Amniotic Egg • Internal fertilization • complete environment for the embryo • egg has a leathery shell • hatch fully developed

•Parts of the egg:

- Yolk: large food supply

- Amnion: filled w/fluid; shock absorber

- Allantois: gas exchange which then goes

to the pores on the shell

- Chorion: transfers nutrients & wastes

Modern Reptiles (3 orders) Order Turtles Order Crocodilia

Order Lizards & Snakes

Maternal Care in Reptiles

• Most fish, amphibians, & reptiles do not provide care for their young

• but alligators & crocodiles stay near the nest & guard the eggs; they often respond to sounds made during hatching, dig out the babies and carry them to water

Birds are vertebrates of the Class Aves

(this class contains about 10,000 different

species)

Some of their characteristics include:

-- endothermic (warm blooded) = they can

regulate their body temperature regardless of

external conditions

-- only animals with

feathers

Characteristics continued,…

-- lay amniotic eggs (an egg that provides a complete environment for the developing embryo) with shells

-- the shell is made of calcium carbonate (CaCO3)

--females lay from 2-8 eggs at one time…these are called a “clutch”

Warm-bloodedness

and flight have enable birds to survive in

virtually every known environment.

Special adaptations for flight:

1. Light-strong skeleton

2. Front appendages modified into

wings

3. Feathers…2 kinds

--contour feathers are used

to fly, give the birds their

coloring and sleek shape

--down feathers are soft,

fluffy and insulating helping the

birds maintain a constant body

temperature

Flight adaptations continued,...

4. Keen senses, especially sight, enable birds

to spot prey

5. Efficient body systems

are necessary because

so much energy is

required for flight.

Birds have a true 4 chambered heart (like us).

Because they have such high metabolism their

heart rate is also very high = over 1000 beats

per minute.

ACCORDING TO SCIENTISTS,…there are not many

fossils of birds around because their bones are so

light and hollow. There has been a lot of debate

about the origin of birds:

- thought to have descended from reptiles

-missing link (225 million yrs)

Protoavis = hollow bones,

no feathers

-missing link (150 million yrs)

Archaeopteryx = feathers,

but solid bone

Mammalian Traits: -Endothermic -Skin/Hides (clothes, footballs) -Hair (even dolphins) -Mammary, Oil, Sweat glands -Maternal care for young

Body Systems: -4 chambered heart -well developed lungs containing alveoli -lobed brain -carnivores have short digestive systems as compared to herbivores

Classification: 1.Monotremes – lay eggs w/tough leathery shells - no nipples, young suck milk from mom’s fur

2. Marsupials – pouched mammals that give birth to tiny immature offspring

--Mostly Australian and neighboring islands --Opossum

Australian Marsupials

3. Eutherians (placentals) – embryos develop inside uterus - Placenta is a sac-like organ that is developed by the growing embryo that attaches to the uterus

--Food & oxygen is absorbed from the mother’s blood. --Umbilical cord attaches embryo to the placenta & takes food & nutrients to the embryo while removing wastes.

Primates -Opposable thumb: grasping hands & feet -Digits have flat nails, not claws -Skin ridges (fingerprints) -Large brain -Flat face

3 Main Groups 1. Lemurs, lorises, pottos

2. Tarsiers

3. Anthropoids (monkeys & apes)

Humans -upright -bipedal -larger brain * language * symbolic thought * manufacture & use complex tools

Hominins Australopiths >human-like hands & teeth >bipedal >”Lucy” >very small body & brain Homo >tools found w/them >larger brain >long, slender legs >size difference between male & female less dramatic

Neanderthals >buried their dead >hunting tools Homo sapiens >genome transformation >cave paintings >natural selection

Trying to find a straight line of human evolution is like herding cats.