It prevents too many sperm from getting to the egg at the same time, because of its viscosity. Proteins in the jelly initiate the acrosome reaction in sperm so they are ready to fertilize the egg. 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)
(d) 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. 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 still surrounded by the fertilization envelope. The blastocoel cavity has begun to form. (c) Cleavage partitions the cytoplasm of one large cell Into many smaller cells called blastomeres Fertilized egg. Shown here is the zygote shortly before the first cleavage division, surrounded by the fertilization envelope. The nucleus is visible in the center. (a) Figure 47.7a–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 Anterior (a) Body axes. The three axes of the fully developed embryo, the tadpole, are shown above. Right Dorsal Ventral Left Posterior Animal hemisphere Animal pole Point of sperm entry 1 The polarity of the egg determines the anterior-posterior axis before fertilization. Vegetal hemisphere Vegetal pole Point of sperm entry At fertilization, the pigmented cortex slides over the underlying cytoplasm 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. 2 Future dorsal side of tadpole Gray crescent First cleavage 3 The first cleavage division bisects the gray crescent. Once the anterior- posterior and dorsal-ventral axes are defined, so is the left-right axis. Figure 47.8a, b (b) Establishing the axes. The polarity of the egg and cortical rotation are critical in setting up the body axes.
SURFACE VIEW CROSS SECTION Animal pole 1 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 cells changing shape and pushing inward from the surface (invagination). Additional cells then roll inward over the dorsal lip (involution) and move into the interior, where they will form endoderm and mesoderm. Meanwhile, cells of the animal pole, the future ectoderm, change shape and begin spreading over the outer surface. Blastocoel Dorsal lip of blastopore Dorsal lip of blastopore Blastula Vegetal pole Archenteron Blastocoel shrinking 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 that becomes smaller as ectoderm spreads downward over the surface. Internally, continued involution expands the endoderm and mesoderm, and the archenteron begins to form; as a result, the blastocoel becomes smaller. 2 Ectoderm 3 Late 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. Blastocoel remnant Mesoderm Endoderm Key Future ectoderm Future mesoderm Figure 47.12 Yolk plug Yolk plug Gastrula Future endoderm The mechanics of gastrulation in a frog
Organogenesis Various regions of the three embryonic germ layers Develop into the rudiments of organs during the process of organogenesis
Neurulation Neural folds LM 1 mm Neural fold Neural plate Notochord Ectoderm Mesoderm Endoderm Archenteron Neural plate formation. By the time shown here, the notochord has developed from dorsal mesoderm, and the dorsal ectoderm has thickened, forming the neural plate, in response to signals from the notochord. The neural folds are the two ridges that form the lateral edges of the neural plate. These are visible in the light micrograph of a whole embryo. (a) Figure 47.14a
Early in vertebrate organogenesis
The notochord forms from mesoderm and the neural plate forms from ectoderm
Neural fold Neural plate Neural crest Outer layer of ectoderm Neural crest Neural tube (b) 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 numerous structures. Figure 47.14b
Eye Somites Tail bud SEM Neural tube 1 mm Notochord Neural crest Coelom Somite Archenteron (digestive cavity) Somites. The drawing shows an embryo after completion of the neural tube. By this time, the lateral mesoderm has begun to separate into the two tissue layers that line the coelom; the somites, formed from mesoderm, flank the notochord. In the scanning electron micrograph, a side view of a whole embryo at the tail-bud stage, part of the ectoderm has been removed, revealing the somites, which will give rise to segmental structures such as vertebrae and skeletal muscle. (c) Figure 47.14c
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 DNA Adenine= A Thymine= T Guanine= G Cytosine= C A always pairs with T C always pairs with G
Bases of RNA Adenine= A Uracil= U Guanine= G Cytosine= C G always pairs with C T from the DNA = A in the RNA A from the DNA = U in the RNA
Chromosomes The 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.
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.
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 While assigned to teach, he was also assigned to tend the gardens and grow vegetables for the monks to eat. 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. Mountains with short, cool growing season meant pea (Pisum sativum) was an ideal crop plant. Gregor Mendel “Father of Genetics”
One Example of Mendel’s Work Tall Dwarf x Phenotype P TT tt Genotype Homozygous Dominant Homozygous Recessive All Tall Clearly Tall is Inherited… What happened to Dwarf? F1 Tt Tall is dominant to Dwarf Heterozygous F1 x F1 = F2 possible gametes Punnett Square: t T 3/4 Tall 1/4 Dwarf F2 Tall Tt Tall TT T possible gametes Dwarf tt Tall Tt t Dwarf is not missing…just masked as “recessive” in a diploid state… there IS a female contribution.
F1 x F1 = F2 F2 possible gametes Punnett Square: t T Tall tt Tall TT T possible gametes Dwarf tt Tall Tt t Mendel as a Scientist Test Cross: Unknown Tall Dwarf x tt possible gametes If Unknown is TT: t t Tall Tt Tall Tt T possible gametes Test Progeny All Tall Tall Tt Tall Tt T 1/3 of F2 Tall are TT 2/3 of F2 Tall are Tt possible gametes If Unknown is Tt: t t Tall Tt Tall Tt T possible gametes Test Progeny Half Tall Half Dwarf Dwarf tt Dwarf tt t
Another Example of Mendel’s Work Green Yellow x Phenotype P gg GG Genotype Homozygous Recessive Homozygous Dominant All Yellow Clearly Yellow is Inherited… What happened to Green? F1 Gg Yellow is dominant to Green Use G/g rather than Y/y for symbolic logic Heterozygous F1 x F1 = F2 possible gametes NEVER use G/Y or g/y Punnett Square: g G 3/4 Yellow 1/4 Green F2 Yellow Gg Yellow GG G possible gametes Green gg Yellow Gg g Green is not missing…just masked as “recessive” in diploid state
F1 x F1 = F2 F2 possible gametes Punnett Square: g G Yellow Gg Yellow GG G possible gametes Green gg Yellow Gg g Mendel as a Scientist Test Cross: Unknown Yellow Green x gg possible gametes If Unknown is GG: g g Yellow Gg Yellow Gg G possible gametes Test Progeny All Yellow Yellow Gg Yellow Gg G 1/3 of F2 Yellow are GG 2/3 of F2 Yellow are Gg possible gametes If Unknown is Gg: g g Yellow Gg Yellow Gg G possible gametes Test Progeny Half Yellow Half Green Green gg Green gg g
After 1900 several scientists tried to replicate Mendel’s crosses using other species including snapdragon. Genetics After Mendel Red Yellow P x PRPR PYPY 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! All Orange F1 PRPY F1 x F1 = F2 possible gametes Punnett Square: PY PR F2 Orange PRPY Red PRPR PR 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. possible gametes Yellow PYPY Orange PRPY PY
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 = red PRPY = orange PYPY = yellow PRp = pink PYp = cream pp = 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 brown HBnHBd = sandy brown HBnhR = auburn HBnhbk = dark brown HBdHBd = blonde HBdhR = strawberry blonde HBdhbk = blonde hRhR = red hRhbk = red hbkhbk = black Recessive can be common! Dominant does NOT mean frequent!
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-recessive is the most common garden pea on Earth! Quantitative Inheritance: multiple genes control trait Highest Crop Yield: AABBCCDDEE Intermediate Crop Yield: AabbCCDdEe Lowest Crop Yield: aabbccddee Darkest Skin Color: AABBCCDDEE Intermediate Skin Color: AaBbCcDdEe Lightest Skin Color: aabbccddee AaBbCcDdEe x AaBbCcDdEe can produce a huge range of colors!
Phenotype = Genotype + Environment Crop Yield = Genotype + Minerals + Water + Light - Pests etc. Optimizing these factors determines agricultural productivity…last part of our course! 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.”
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 Populations Recessive autosomal disease; relentless deterioration of mental and physical abilities Hybrid Vigor: Wild Corn A x Wild Corn B High Yield Hybrid Corn!
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.
Trophic level: All the organisms that are the same number of food-chain steps from the primary source of energy Modified from: General Ecology, by David T. Krome
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.
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
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
Primary Succession Simple plants like mosses and ferns can grow in the new soil http://www.uncw.edu http://uisstc.georgetown.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
Symmetry Arrangement of parts with regard to the axes and planes. Way a body parts is arranged around a center point 4 fundamental types of animal symmetry: Spherical or universal Radial Biradial or radiobilateral Bilateral
Asymmetry Anaxial symmetry Body cannot be divided by planes into similar halves Body is irregularly shaped No definite anatomical relationship between different parts
Universal or Spherical Homoaxial symmetry Symmetry 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 ball Body parts arranged concentrically around or radiating from a central point
Radial Symmetry Monoaxialheteropolar 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.
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 Forms Metamerism – 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)
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: Plants and Animals into more groups Based his system on specific traits Gave organisms names that described their traits
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
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
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
There are two Cnidarian body plans Polyp outer epithelium (epidermis) mesoglea (matrix) inner epithelium (gastrodermis) Medusa
reproductive polyp female medusa male medusa sperm ovum Life cycle of Obelia feeding polyp zygote planula polyp forming branching one branch from a mature colony
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 Planaria, a free-living flatworm opening of tubule at body surface flame cell
b A definitive host eats infected, undercooked beef a Larvae become encysted in intermediate host tissues c Scolex of larva attaches to intestine’s wall d Many proglottids form by budding f Cattle may ingest embryonated eggs or ripe proglottids to become intermediate hosts e Ripe proglottids containing fertilized eggs leave host in feces 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
Body Plan of a Roundworm gonad pharynx intestine eggs in uterus anus false coelom muscularized body wall Caenorhabditiselegans
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.
Body Plan of a Snail anus gill mantle cavity excretory organ heart digestive gland shell stomach mantle radula foot
Body Plan of a Cuttlefish esophagus stomach kidney digestive gland brain arm jaw mantle reproductive organ internal shell siphon ink sac heart accessory heart tentacle radula anus gill
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.
italicized if typed or underlined if hand written. Example: Felis concolor or F. concolor Which is the genus? The species?
"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.