bio22 4th post lab discussion

4th Post lab discussionBio22 LManahan

Embryology

Development of embryo Fertilization Cleavage Gastrulation Neurulation Organogenesis

Fertilization

Fertilization membrane Hardened vitelline membrane to prevent further

sperm penetration

Perivitelline space Grey crescent

Jelly coats1. It prevents too many sperm from getting to

the egg at the same time, because of its viscosity.

2. Proteins in the jelly initiate the acrosome reaction in sperm so they are ready to fertilize the egg.

3. It provides a sort of "shock absorber" to prevent injury .

Figure 32.1 Early es,mbryonic development (Layer 1)

Cleavage is a series of rapid mitotic divisions (without cell growth)

Cleavage partitions the cytoplasm of one large cell Into many smaller cells called blastomeres

Figure 47.7a–d

Fertilized egg. Shown here is thezygote shortly before the first cleavage division, surrounded by the fertilization envelope. The nucleus is visible in the center.

(a) Four-cell stage. Remnants of the mitotic spindle can be seen between the two cells that have just completed the second cleavage division.

(b) Morula. After further cleavage divisions, the embryo is a multicellular ball that is stillsurrounded by the fertilization envelope. The blastocoel cavityhas begun to form.

(c) Blastula. A single layer of cells surrounds a large blastocoel cavity. Although not visible here, the fertilization envelope is still present; the embryo will soon hatch from it and begin swimming.

(d)

These cells are pluripotent (have the potential to become ANY of the 220 types of cells in the human body). These are embryonic stem cells

Which is holoblastic and which is meroblastic?

The development of body axes in frogs Is influenced by the polarity of the egg

Figure 47.8a, b

Anterior

Ventral

Left

Posterior

Dorsal

Right

Body axes. The three axes of the fully developed embryo, thetadpole, are shown above.(a)

Animalhemisphere

Animal polePoint ofsperm entry

Vegetalhemisphere Vegetal pole

Point ofspermentry Future

dorsalside oftadpoleGray

crescentFirstcleavage

The polarity of the egg determines the anterior-posterior axis before fertilization.

At fertilization, the pigmented cortex slides over the underlyingcytoplasm toward the point of sperm entry. This rotation (red arrow)exposes a region of lighter-colored cytoplasm, the gray crescent, which is a marker of the dorsal side.

The first cleavage division bisects the gray crescent. Once the anterior-posterior and dorsal-ventral axes are defined, so is the left-right axis.

(b) Establishing the axes. The polarity of the egg and cortical rotation are critical in setting up the body axes.

1

2

3

The mechanics of gastrulation in a frog

Figure 47.12

SURFACE VIEW CROSS SECTIONAnimal pole

Blastocoel

Dorsal lipof blastopore

Dorsal lipof blastoporeVegetal pole Blastula

Blastocoelshrinking

Archenteron

Blastocoelremnant

EctodermMesoderm

Endoderm

GastrulaYolk plugYolk plug

Key

Future ectoderm

Future mesoderm

Future endoderm

Gastrulation begins when a small indented crease, the dorsal lip of the blastopore, appears on one side of the blastula. The crease is formed by cellschanging shape and pushing inward from the surface (invagination). Additional cells then rollinward over the dorsal lip (involution) and move intothe interior, where they will form endoderm andmesoderm. Meanwhile, cells of the animal pole, the future ectoderm, change shape and begin spreading over the outer surface.

The blastopore lip grows on both sides of the embryo, as more cells invaginate. When the sides of the lip meet, the blastopore forms a circle thatbecomes smaller as ectoderm spreads downward over the surface. Internally, continued involutionexpands the endoderm and mesoderm, and the archenteron begins to form; as a result, the blastocoel becomes smaller.

1

2

3Late in gastrulation, the endoderm-lined archenteron has completely replaced the blastocoel and the three germ layers are in place. The circular blastopore surrounds a plug of yolk-filled cells.

Organogenesis

Various regions of the three embryonic germ layers Develop into the rudiments of organs

during the process of organogenesis

Neurulation

Early in vertebrate organogenesis The notochord forms from

mesoderm and the neural plate forms from ectoderm

Figure 47.14a

Neural plate formation. By the timeshown here, the notochord has developed from dorsal mesoderm, and the dorsal ectoderm hasthickened, forming the neural plate, in response to signals from thenotochord. The neural folds arethe two ridges that form the lateral edges of the neural plate. These are visible in the light micrographof a whole embryo.

Neural folds

1 mmNeuralfold

Neuralplate

NotochordEctoderm

MesodermEndodermArchenteron

(a)

LM

The neural plate soon curves inward Forming the neural tube

Figure 47.14b

Formation of the neural tube. Infolding and pinching off of the neural plate generates the neural tube. Note the neural crest cells, which will migrate and give rise to numerousstructures.

Neuralfold

Neural plate

Neural crest

Outer layer of ectodermNeural crest

Neural tube

(b)

Mesoderm lateral to the notochord Forms blocks called somites

Lateral to the somites The mesoderm splits to

form the coelom

Figure 47.14c

Somites. The drawing shows an embryoafter completion of the neural tube. By this time, the lateral mesoderm hasbegun to separate into the two tissuelayers that line the coelom; the somites, formed from mesoderm, flank thenotochord. In the scanning electron micrograph, a side view of a whole embryo at the tail-bud stage, part of the ectoderm has been removed, revealingthe somites, which will give rise to segmental structures such as vertebrae and skeletal muscle.

Eye Somites Tail bud

1 mmNeural tube

Notochord Neuralcrest

Somite

Archenteron(digestive cavity)

Coelom

(c)

SEM

neurula

Level of telencephalon

Level of eyes

Level of heart

http://www.uoguelph.ca/zoology/devobio/57mmfrog/db57fg11.htm

Level of midgut

Level of hindgut

GENETICS

Vocabulary

Genetics: The scientific study of heredity Allele: Alternate forms of a gene/factor. Genotype: combination of alleles an organism

has. Phenotype: How an organism appears. Dominant: An allele which is expressed (masks

the other). Recessive: An allele which is present but

remains unexpressed (masked) Homozygous: Both alleles for a trait are the

same. Heterozygous: The organism's alleles for a trait

are different.

Composition of DNA

The structure of DNA was discovered by Watson and Crick in 1953.

It is a twisted double helix molecule, containing sugar, phosphates, and nitrogenous bases.

The sugar is deoxyribose and the phosphoric acid molecules are always the same and provides for the structure (side of the ladder).

The only difference between us is the order and arrangement of the four bases (rungs of the ladder).

Bases of DNAAdenine= AThymine= TGuanine= GCytosine= CA always pairs with TC always pairs with G

Bases of RNAAdenine= AUracil= UGuanine= GCytosine= CG always pairs with CT from the DNA = A in the RNAA from the DNA = U in the RNA

DNA Model

ChromosomesThe DNA in every cell is located in

rod like segments called chromosomes

Chromosomes occurs in pairs in every cell of our body except in the sperm and ovum.

Chromosomes numbers are the same for each specie.

Chromosome Numbers

Species Diploid # Haploid #

Cattle 60 30Swine 38 19Sheep 54 27Horse 64 32Human 46 23Chicken 78 39Goat 60 30Donkey 62 31

Chromosomes

There are 2 sex chromosomes included in the diploid number of the chromosomes.

All of the other chromosomes are referred to as autosomes.

In mammals if the sex chromosomes are alike, XX it results in a female.

If the sex chromosomes are different, XY it results in a male.

Sex Determination Females contribute an X chromosome

towards the sex of their offspring. Males can contribute an X or a Y

chromosome toward the sex of their offspring.

Absence of an Y chromosome results in a the embryo developing into a female.

Presence of an Y chromosome results in the embryo developing into a male.

Sex Determination Gametogenesis =

Formation of gametes through meiosis.

Male = 4 viable spermatids

Female = 1 viable ovum, 3 polar bodies.

Laws of Inheritance

Law of Segregation: When gametes (sperm egg etc…) are formed each gamete will receive one allele or the other.

Law of independent assortment: Two or more alleles will separate independently of each other when gametes are formed

Mendelian Genetics

Gregor Mendel“Father of Genetics”

Augustinian Monk at Brno Monastery in Austria (now Czech Republic)

Not a great teacher but well trained in math, statistics, probability, physics, and interested in plants and heredity.

While assigned to teach, he was also assigned to tend the gardens and grow vegetables for the monks to eat.

Mountains with short, cool growing season meant pea (Pisum sativum) was an ideal crop plant.

Mendel worked with peas (Pisum sativum)• Good choice for environment of monastery• Network provided unusual varieties for testing• Obligate self-pollination reproductive system

Permits side-by-side genetic barriers

Cross-pollinations require intentional process• Crosses meticulously documented• Crosses numerically/statistically analyzed

TallP

Dwarfx

F1All Tall

Phenotype

One Example of Mendel’s Work

Clearly Tall is Inherited…What happened to Dwarf?

F1 x F1 = F2

F23/4 Tall1/4 Dwarf

Dwarf is not missing…just masked as “recessive” in a diploid state… there IS a female contribution.

Tall is dominant to Dwarf

TT tt

Tt

Genotype

HomozygousDominant

HomozygousRecessive

Heterozygous

Dwarftt

TallTt

t

TallTt

TallTT

T

tTPunnett Square:

possible

gametes

possible gametes

Unknown Tall Dwarfx

Mendel as a Scientist

tt

TallTt

TallTt

T

TallTt

TallTt

T

tt

possible

gametes

possible gametes

F1 x F1 = F2F2

Dwarftt

TallTt

t

Talltt

TallTT

T

tTPunnett Square:

possible

gametes

possible gametesTest Cross:

If Unknown is TT:

Dwarftt

Dwarftt

t

TallTt

TallTt

T

tt

possible

gametes

possible gametesIf Unknown is Tt:

Test Progeny All Tall

Test Progeny Half Tall Half Dwarf

1/3 of F2 Tall are TT2/3 of F2 Tall are Tt

GreenP

Yellowx

F1All Yellow

Phenotype

Another Example of Mendel’s Work

Clearly Yellow is Inherited…What happened to Green?

F1 x F1 = F2

F23/4 Yellow1/4 Green

Green is not missing…just masked as “recessive” in diploid state

1. Yellow is dominant to Green

2. Use G/g rather than Y/y for symbolic logic

gg GG

Gg

Genotype

HomozygousRecessive

HomozygousDominant

Heterozygous

Greengg

YellowGg

g

YellowGg

YellowGG

G

gGPunnett Square:

possible

gametes

possible gametes NEVER use G/Y or g/y

Unknown Yellow Greenx

Mendel as a Scientist

gg

YellowGg

YellowGg

G

YellowGg

YellowGg

G

gg

possible

gametes

possible gametes

F1 x F1 = F2F2

Greengg

YellowGg

g

YellowGg

YellowGG

G

gGPunnett Square:

possible

gametes

possible gametesTest Cross:

If Unknown is GG:

Greengg

Greengg

g

YellowGg

YellowGg

G

gg

possible

gametes

possible gametesIf Unknown is Gg:

Test Progeny All Yellow

Test Progeny Half Yellow Half Green

1/3 of F2 Yellow are GG2/3 of F2 Yellow are Gg

Mendel worked with peas (Pisum sativum)• Good choice for environment of monastery• Network provided unusual varieties for testing• Obligate self-pollination reproductive system

Permits side-by-side genetic barriers

Cross-pollinations require intentional process• Crosses meticulously documented• Crosses numerically/statistically analyzed• Scientists of 1860s could not understand math• Work lost in journals for 50 years!• Rediscovered in 1900s independently by 3 scientists• Recognized as landmark work!

Genetics After MendelRed

xYellow

All Orange

When these alleles go walking, they both do some talking (codominance)!

OK, so we cannot use R/r nor Y/y so we pick a third letter…P for the petal color gene.

Notice: we do NOT mix R/Y or r/y!

PRPR PYPY

PRPY

F1 x F1 = F2

F2

YellowPYPY

Orange

PRPY

PY

Orange

PRPY

RedPRPRPR

PYPRPunnett Square:

possible

gametes

possible gametes

P

F1

This F2 will NOT have a 3:1 ratio of phenotypes.

Instead it shows a 1:2:1 ratio!

The exception here proves the rule.

After 1900 several scientists tried to replicate Mendel’s crosses using other species including snapdragon.

In addition to this, there are multiple alleles possible:

PR = red PY = yellow p = no pigment

The combination of alleles in a diploid determine the flower color:

PRPR = redPRPY = orangePYPY = yellow

PRp = pinkPYp = creampp = white

Human hair color follows a similar pattern:

Alleles: HBn = brown HBd = blonde hR = red hbk = black

The combinations of these alleles determine the base hair color:

HBnHBn = dark brownHBnHBd = sandy brownHBnhR = auburnHBnhbk = dark brown

HBdHBd = blondeHBdhR = strawberry blondeHBdhbk = blonde

hRhR = redhRhbk = red

hbkhbk = black

Dominant does NOT mean frequent!Recessive can be common!

Another Example of Recessive Being Common: Pisum sativum

Garden Peas: green seed, wrinkled seed, dwarf stature, white flower

gg ww dd aa

In other words: a quadruple double-recessiveis the most common garden pea on Earth!

Quantitative Inheritance: multiple genes control trait

Highest Crop Yield: AABBCCDDEEIntermediate Crop Yield: AabbCCDdEe Lowest Crop Yield: aabbccddee

Darkest Skin Color: AABBCCDDEEIntermediate Skin Color: AaBbCcDdEe Lightest Skin Color: aabbccddee

AaBbCcDdEe x AaBbCcDdEe can produce a huge range of colors!

Phenotype = Genotype + EnvironmentCrop Yield = Genotype

+ Minerals + Water + Light - Pests

etc.

Human Skin Color = Genotype

+ Sun (UV) Exposure

- Aging Factors

The sun exposure effect is most obvious in people of intermediate skin base color

but everyone can have “tan lines.”

Optimizing these factors determines agricultural productivity…last part of our course!

Who Gets To Mate With Whom? …Two Extremes

Inbreeding Depression: related parents give same recessives to children

Hemophilia: Queen Victoria’s Mutation and Diseased Grandchildren

 recessive sex-linked, X chromosome disorders, haemophilia is more likely to occur in males than females

Tay-Sachs: Jewish PopulationsRecessive autosomal disease; relentless deterioration of mental and physical abilities

Hybrid Vigor:

Wild Corn A x Wild Corn B

High Yield Hybrid Corn!

Tree method crossing of two traits(dihybrid)

Continuous Variation

Many traits may have a wide range of continuous values. Eg. Human height can vary considerably. There are not just "tall" or "short" humans

Gene interaction: Many biological pathways are governed by

multiple enzymes, involving multiple steps. If any one of these steps are altered. The end product of the pathway may be disrupted.

Environmental effects: Sometimes genes will not be fully expressed

owing to external factors. Example: Human height may not be fully expressed if individuals experience poor nutrition.

The Average American Phenotype

Ecosystems: Basic Concepts

What is an ecosystem?System = regularly

interacting and interdependent components forming a unified whole

Ecosystem = an ecological system;= a community and its physical environment treated together as a functional system

Ecosystem Services

The human economy depends upon the services performed for free by ecosystems.

The ecosystem services supplied annually are worth many trillions of dollars.

Economic development that destroys habitats and impairs services can create costs to humanity over the long term that may greatly exceed the short-term economic benefits of the development.

These costs are generally hidden from traditional economic accounting, but are nonetheless real and are usually borne by society at large. http://www.epa.gov/watertrain/pdf/issue2.pdf

Ecosystems:Fundamental Characteristics

Structure: Living (biotic) Nonliving (abiotic)

Process: Energy flow Cycling of matter (chemicals)

Change: Dynamic (not static) Succession, etc.

Abiotic components:

ABIOTIC components: Solar energy provides practically all the

energy for ecosystems. Inorganic substances, e.g., sulfur, boron,

tend to cycle through ecosystems. Organic compounds, such as proteins,

carbohydrates, lipids, and other complex molecules, form a link between biotic and abiotic components of the system.

BIOTIC components

The biotic components of an ecosystem can be classified according to their mode of energy acquisition.

In this type of classification, there are: Autotrophs and Heterotrophs Organisms that produce their own food

from an energy source, such as the sun, and inorganic compounds.

Organisms that consume other organisms as a food source.

Modified from: General Ecology, by David T. Krome

Trophic level: All the organisms that are the same number of food-chain steps from the primary source of energy

Trophic Levels

A trophic level is the position occupied by an organism in a food chain.

Trophic levels can be analyzed on an energy pyramid.

Producers are found at the base of the pyramid and compromise the first trophic level.

Primary consumers make up the second trophic level.

Secondary consumers make up the third trophic level.

Finally tertiary consumers make up the top trophic level.

Trophic Levels Found on an Energy Pyramid

The greatest amount of energy is found at the base of the pyramid.

The least amount of energy is found at top of the pyramid.

Source: corpuschristiisd.org/user_files/91702/Ecosystem.ppt

Food Chains

The producers, consumers, and decomposers of each ecosystem make up a food chain.

There are many food chains in an ecosystem.

Food chains show where energy is transferred and not who eats who.

Example of a Food Chain

Food Webs All the food chains in an area make up the food web of the

area.

Changes in Ecosystems:Ecological Succession

Definition:

Natural, gradual changes in the types of species that live in an area; can be primary or secondary

The gradual replacement of one plant community by another through natural processes over time

Primary Succession

Begins in a place without any soil Sides of volcanoes Landslides Flooding

Starts with the arrival of living things such as lichens that do not need soil to survive

Called PIONEER SPECIES

http://botit.botany.wisc.edu

http://www.saguaro-juniper.com/

Primary Succession

Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces

When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

http://www.life.uiuc.edu

Primary Succession

Simple plants like mosses and ferns can grow in the new soil

http://uisstc.georgetown.edu

http://www.uncw.edu

Primary Succession

The simple plants die, adding more organic material

The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

http://www.cwrl.utexas.edu

Primary Succession

These plants die, and they add more nutrients to the soil

Shrubs and tress can survive now

http://www.rowan.edu

Primary Succession

Insects, small birds, and mammals have begun to move in

What was once bare rock now supports a variety of life

http://p2-raw.greenpeace.org

Secondary Succession

Begins in a place that already has soil and was once the home of living organisms

Occurs faster and has different pioneer species than primary succession

Example: after forest fires

http://www.geo.arizona.edu

Climax Community

A stable group of plants and animals that is the end result of the succession process

Does not always mean big trees Grasses in prairies Cacti in deserts

Symmetry and Body Plan

SymmetryArrangement of parts with regard to

the axes and planes.Way a body parts is arranged around

a center point4 fundamental types of animal

symmetry: Spherical or universal Radial Biradial or radiobilateral Bilateral

Asymmetry

Anaxial symmetryBody cannot be divided by planes

into similar halvesBody is irregularly shapedNo definite anatomical relationship

between different parts

Asymmetry

Universal or Spherical

Homoaxial symmetrySymmetry exists in an organism that

can be dissected into equal or identical halves by any of the infinite axes and planes that transect it.

Assumes shape of ballBody parts arranged concentrically

around or radiating from a central point

Universal

Radial Symmetry

Monoaxial heteropolar symmetry Organism assumes shape of a cylinder

with parts arranged around and along a single central axis in which 2 ends are different: mouth and anus

Central axis is referred as longitudinal, oral-aboral or antero-posterior axis.

Plane passing through axis dividing organism into similar halves.

Radial Symmetry

Biradial symmetry

Dissymmetry

Bilateral Symmetry

only the transverse axis has similar ends.

Antero-posterior axis and dorso-ventral axis

Divides animal into right and left with mirror images

Bilateral Symmetry

Asymmetrical – without a balanced arrangement of similar parts on either side of a point or axis

Radial - any plane passing through the oral-aboral axis divides an organism to mirror images

Bilateral – only the midsagittal plane divides an organism to mirror images. Have definite anterior (head) and posterior (tail) ends

Other Features of animal Forms

Antimeres – identical and asymmetrically corresponding parts of an animal.

Arms of a starfish

Other Features of Animal FormsMetamerism – division

of body into segments or metameres. Segmentation may be

superficial or external (false) OR may include internal organs (true)

Segments may be similar (homonomous) OR different from each other (heternomous)

Other Features of Animal Forms

Cephalization – differentiation of anterior end of animal and is characterized by concentration of nervous elements such as formation of brain and sense organs.

Well-developed head region

Other Features of Animal Forms

Tagmatization or tagmosis – union of segments into larger functional groups. Each special group is a tagma (plural,

tagmata)

Animal Diversity

Why Things are Grouped

Put things in order Easier to find Show that things share certain traits

Methods of Classification Early Classification

Aristotle ▪ Plants and Animals▪ Plants (Green & Didn’t Move)▪ Animals (Weren’t Green & Move)

Aristotle’s Classification

Animals Land, Water, Air

Plants Size of plant Pattern of Growth

Aristotle’s Classification

Methods of Classification New Classification

Carolus Linnaeus (1735)▪ 2 main groups: Kingdom▪ Use specific traits into same group and called it species

▪ Placed similar species to larger group called genus

Linnaeus

Important Changes in Aristotle’s System:

1. Plants and Animals into more groups2. Based his system on specific traits3. Gave organisms names that described

their traits

- Living things had 2-part names:Genus species

Classification System

Classifying Organisms

Kingdom Phylum Class Order Family Genus Species

Comparing Classification groups and address informationCountry Kingdom

State Phylum

County Class

Town Order

Neighborhood Family

Street Genus

House number Species

Classification

How Scientists Classify Today

Look at Traits Compare traits of one organism with

those of another. Compare organisms living today

with those that lived long ago.

Classifying Based on How Organisms are Related

Classifying the House Cat

Other Evidence Used in Classifying Based on living thing’s ancestors

Horses and donkeys have many same ancestors

Similar body structures Human and cat have similar front limbs

and similar bones arranged in similar patterns

Body chemistry Horseshoe crab’s blood is similar to

spider

Scientific Name Comes from Classification

Why Scientific Names are Used

No mistakes can be made about which living thing is described.

Scientific names seldom change. Scientific names are written in

the same language around the world.

Kingdom Classification

AnimalPlantFungiProtistMonera

Modern Classification

Seven groups – Kingdom, phylum, class, order, family, genus, species

Evidence – Same ancestors, similar body structure, body chemistry

Organisms given 2-part scientific names

Kingdoms – Moneran, Protist, Fungus, Plant, Animal

Overview of Animal Diversity and Phylogeny

Diversified during Precambrian and Cambrian periods

Monophyletic Parazoans-first branch, lack true

tissues Radiata and bilateria two major

branches of Eumetazoa Evolution of body cavities Protostomes and deuterostomes

Parazoa

Sponges “beside the animals” Simple aquatic and marine forms

Eumetazoa

Two major branches: 1. Radiata-radial symmetry, top and

bottom, no front, back, or sides,

diploblastic larva 2. Bilateria-bilateral symmetry,

triploblastic, cephalization

Importance of Coelom

Acoelomates-no body cavity, Platyhelminthes

Pseudocoelomates-fluid filled body cavity, partially lined with mesoderm, Nematoda

Coelomates-fluid filled, completely lined with mesoderm, Annelida

Coelom-body cavity that protects internal organs

Protostomes and Deuterostomes

Protostomes: Mollusks,

Annelids, Arthropods

Spiral cleavage Determinate

cleavage Blastopore forms

the mouth schizocoelous

Deuterostomes: Echinoderms and

Chordates Radial cleavage Indeterminate

cleavage Blastopore forms

the anus Enterocoelous

The Origins of Animal Diversity

Colonial protist origin during Cambrian Explosion

Evidence from fossil beds: Burgess Shale, Yunnan region, Greenland

Why such rapid diversification?1. Adaptive radiation2. Predator-prey relationships3. Higher concentration of oxygen

Porifera - Sponges

No symmetryNo organsThe least complex animalsAquatic in fresh and marine

environments

central cavity

water out

water in

flagellummicrovilli nucleus

glasslike structural elementsamoeboid cell

poresemifluid matrixflattened surface cells

Body Plan of a Sponge

Venus’s flower basket (Euplectella)

Cnidaria

Radial symmetry Body has only 2 cell layers Mouth surrounded by tentacles with stinging cells Aquatic, FW and marine Include jellyfish, corals, sea anemones, hydra Some are motile, and all have a very simple

nervous system Respiration: direct gas exchange with aquatic

surroundings

outer epithelium (epidermis)

mesoglea(matrix)

inner epithelium

(gastrodermis)Medusa

Polyp

There are two Cnidarian body plans

reproductive polyp

female medusa male medusa

sperm

zygote

ovum

planulapolyp forming

branching

one branch from a mature colony

feeding

polyp

Life cycle of Obelia

Flatworms - Platyhelminthes Body has 3 cell layers: ectoderm, mesoderm and

endoderm Bilateral symmetry Parasitic and free -living aquatic (fw and marine)

and terrestrial: tapeworms, flukes, and Planaria Digestive system with one opening Primitive nervous system Hermaphroditic Respiration through skin

pharynx (protruded)

protonephridia

flame cell nucleus

cilia

fluid filters through membrane folds

flame cell

opening of tubule at body surface

Planaria, a free-living flatworm

brain nerve cord

genital pore

oviduct

testis

ovary

penis

a Larvae become encysted in intermediate host tissues

b A definitive host eats infected, undercooked beef

d Many proglottids form by budding

e Ripe proglottids containing fertilized eggs leave host in feces

f Cattle may ingest embryonated eggs or ripe proglottids to become intermediate hosts

c Scolex of larva attaches to intestine’s wall

Tapeworm life cycle

Roundworms - Nematoda Digestive system with mouth and anus

(“complete”) Separate sexes Aquatic and terrestrial, free living and

parasitic Body cavity gives “tube within a tube”

construction Respiration through skin, no circulatory

system

gonadpharynx intestine

false coelom

eggs in uterus anus

muscularized body wall

Caenorhabditis elegans

Body Plan of a Roundworm

 Life cycle of Schistosoma japonicum

Mollusks - Mollusca

Often but not always have external shell Includes clams, oysters, snails, slugs,

squid, octopus, scallops, chambered nautilus

Body is soft with bilateral symmetry Nervous system, circulatory system,

respiratory system Some have excellent sense organs and

large brains, and can learn easily.

anus gillmantle cavity

radula

excretory organ

heart

stomach

shell

footmantle

digestive gland

Body Plan of a Snail

stomachkidneyesophagus

digestive gland

brain

arm

jaw

tentacle radula

siphon

anusink sac gill

heart accessory heart

reproductive organ

mantleintern

al shell

Body Plan of a Cuttlefish

Segmented Worms - Annelida Body composed of many identical

segments. Allows more specialization Aquatic or terrestrial Includes clam worm, feather worms,

leeches, and earthworm. These animals have “all” systems, and are

quite complex. They are most likely the ancestors of the Arthropods, the most successful Phylum of animals on Earth.

“jaws”

toothlike structurespharynx (everted)

antenna

palp (food handling)tentacle

eyes

chemical-sensing pit

parapod

• Taxonomy is the science of grouping

and naming organisms.

• Classification the grouping of information or objects based on similarities.• The scientific name comes from one of two

“dead” languages – Latin or ancient Greek.

    • a two name system for writing scientific names.

• The genus name is written first (always Capitalized).    

• The species name is written second (never capitalized).    

• Both words are italicized if typed or underlined if hand

written.

Example: Felis concolor or F. concolor

Which is the genus? The species?    

Binomial Nomenclature

"Formal" scientific names should have a third part, the authority.     The authority is not italicized or underlined.

The authority is written as an abbreviation of the last name of the person responsible for naming the organism. Since Carolus Linnaeus was the first person to name many plants, the L. for Linnaeus is very common in plant scientific names.

An example is Quercus alba L.