This web page represents a distillation of the major ideas and information associated with the Biological Science (BIOL 1003) lecture course.   References to page numbers, Figures, and Tables, are associate with reading assignments Asking about Life by Tobin and Dusheck - reading assignments are noted in the Syllabus for BIOL 1003.002 for additional information.   If you note any errors in the following document, I'd appreciate it if you would bring this to my attention.  Email address: mhuss@astate.edu.

BIOTECHNOLOGY:  GENETIC ENGINEERING, GENE THERAPY, AND OTHER PRACTICAL APPLICATIONS

As an understanding of the molecular basis for heredity has grown over the last century, so have the tools for manipulating genetic material and cells (e.g., DNA, RNA, cloning) in the laboratory has exploded to form the biotechnological revolution.  DNA can be extracted from any organism, genes identified, their nucleotide sequences elucidated, manipulated and maneuvered into the genome (genetic make-up) of other related or non-related organisms.

Restriction enzymes can act as "molecular scissors" in cutting apart DNA at specific "recognition sites" within the molecule (refer to Figure 13-5  page 282 in the textbook).  Other enzymes can be used as "molecular glue" to paste different sections back together; these enzymes are called ligases - refer to Figure 13-6  page 283 in the textbook.  As a result, genes harvested from one organism can be inserted into the DNA of another organism usually with the assistance of some vector (e.g., bacterial plasmid, attenuated or non-virulent virus).  There are now bacteria that carry the human gene for insulin.  Insulin once only harvested from animals is now harvested from bacteria capable of producing the same insulin protein produced by a human pancreas.  This source of insulin is used in the treatment of diabetes.  In another example, genes that result in bioluminescence in lightening bugs or fireflies has been introduced into tobacco plants to produce plants that are capable of glowing in the dark.  A trait that these plants did not previously carry.  The introduction of foreign DNA or genes via some mechanism into another organism is referred to as Transformation, and is a prerequisite for creating Transgenic or Genetically-Modified (GM) Organisms - refer to Figures 13-4, 13-5, 13-12, 13-13 on pages 281, 290, 291, and 293 in the textbook.

Transgenic organisms are produce by:

   1.  Addition of new genes (to express a new gene product).
   2.  Suppression of a gene or a gene product

Potential Benefits of Genetic Engineering

• Gene therapies that treat certain disorders at the source of the problem instead of treating the symptoms.
• Plants capable of synthesizing oils, starches, and plastics (e.g., cotton with the polyester blend built in to the cellulose fibers?)
• More nutritious foods (e.g., plants with a higher protein content, and wider profile of essential amino acids - methionine-rich beans or lysine-rich corn).
• Plants capable of fixing their own atmospheric nitrogen for growth, resulting in less need to fertilize crops.
• Freeze, pest, herbicide, and disease resistant crops.
• Bacteria, yeast, plants, and animals (particularly through collection of milk) capable of producing pharmaceutical substances (e.g., medicines, drugs, and vaccines).
• Transgenic swine that have to the human immune system appear to be human-like, resulting in a source of animals to be used as organ donors for transplant recipients (e.g., heart, kidney).
• Novel pets (e.g., GloFish^TM - http://www.glofish.com/photos.asp or http://www.cnn.com/2003/TECH/science/12/04/fluorescent.fish.ap/). 

Potential Problems of Genetic Engineering

• Allergies to transformed biological products.
• Accidental creation of disease-causing agents in plants, animals, and humans.
• Accidental movement of novel genes into wild relatives of cultivated plants.
• Consumer resistance to using genetically-modified plant products, especially food.
• Ethical and moral considerations. (e.g., releasing transgenic marijuana plants that are poisonous, exploitation of genetic resources for personal gain; cloning genetically-modified humans).

Molecular Forensics

Fragments of DNA digested with restriction enzymes can be separated through a process of "electrophoresis" (refer to Figure 13-2 on page 278 in the textbook) to create a "DNA fingerprint".  In humans, DNA fingerprints are unique (except between identical twins or among identical triplets, etc.).  Polymerase Chain Reaction (PCR) is used to "amplify" or increase the amount of DNA biological samples when small amounts are available (e.g., blood skin, hair follicles, semen, etc.); refer to Figure 6-17 on page 179 in the textbook.  The ability to do this is especially useful in comparing biological samples left behind at a crime scene and the opportunity for criminologists to link a suspect to a crime by comparing their DNA fingerprint with the sample DNA.   This technique is also useful in linking the remains of unidentified human remains with a missing or dead person.

Over 1.5 million species of organisms have been described by biologists.  Classification of life's diversity contributes to our understanding of biology.  Initially, naturalist's, especially during the 18th and first part of the 19th century, were interested in classifying life's diversity in an effort to gain a broad view of the "Divine Master Plan" (see the third set of notes for further discussion of  The Great Chain of Being).  Carl von Linne (AKA, Carolus Linnaeus - 1707-1778) developed criteria and methods for describing and assigning species names to newly discovered group of organisms.  His system of naming was called Binomial Nomenclature, two word naming system, in which each species was assigned a two word name, the genus and specific epithet.  (NOTE: IN REVIEW READING MATERIAL IN THE TEXTBOOK, THE BOOK IS IN ERROR BY SAYING THAT THIS TWO WORD NAME IS COMPRISED OF A GENUS AND SPECIES NAME; THE SPECIES NAME IS ACTUALLY MADE UP OF THE GENUS AND THE SPECIFIC EPITHET - refer to Figure 19-3 on page 423 in the textbook.

Examples of species include:

• Escherichia coli  or Escherichia coli or a bacterium found in the gut of mammals
• Quercus alba or Quercus alba L. or white oak, originally named by Linnaeus, hence the L.; the term alba means "white".
• Homo sapiens or Homo sapiens or human being; Homo = man, sapiens = wise.  Wise man.
• Smittium boomerangum or Smittium boomerangum Williams & Lichtwardt 1990, an insect gut fungus with boomerang-shaped spores and first observed and described in Australia.
• Morchella esculenta or Morchella esculenta or the yellow morel mushroom; the term esculenta means "edible".
• Zea mays or Zea mays or maize or corn.

Note that in the previous example that the first letter of the genus name is upper case; all other letters are lower case.  The species name is italicized or underlined.  The author(s) name or initials may or may not appear after the species name.  The author(s) are the folks who originally published a written description (in their native language and in latin).  The specific epithet is often descriptive of some aspect of the species.

Linnaeus and taxonomist describe a species based on one or a few species, which are then store in a museum or herbarium collection.  The specimen used as the basis for a species description is called the type specimen.  A type specimen becomes the archetype for the entire species.

Species are classified into ever broader encompassing categories.  The broadest category is the domain.  There are three domains:  Archaea, Bacteria, and Eukarya - refer to Figure 1-10 on page 17 in the textbook.  Members of the domains Archaea and Bacteria are prokaryotes (refer to Figure 20-6 on page 439 in the textbook) while members of the domain Eukarya are eukaryotes (refer to Figure 4-5 on page 79 in the textbook).  The next largest category is the Kingdom level.  Only one kingdom is found in domain Archaea, that is, Archaebacteria.  One kingdom represents the domain Bacteria, that is, Eubacteria (the "true" bacteria - bacteria and cyanobacteria).  In prior classification schemes members of the domains Archaea and Bacteria use to be classified together into a single kingdom called Monera.  The Domain Eukarya contains all types of eukaryotic organisms from single-celled to multicellular forms.  Four kingdoms are found in the domain Eukarya (Kingdoms Protist, Plant, Fungi, and Animal).

Of the various taxonomic categories, it is generally recognized that all levels of organizations are artificial, and the only level that is biologically-significant is the species level. 

FIVE OR SIX KINGDOM SYSTEM OF CLASSIFICATION --- The following table lists characteristics common among living organisms found in the five kingdoms.  Viruses are not included in this scheme - refer to Table 401 on page 77 in the textbook..
 

^aAs a consumer, it acts primarily as a parasite or pathogen (disease-causing organism).

^bConsumers include herbivores (plant-eaters), carnivores (meat-eaters), omnivores (mixed-diet feeders), detritivores (feeding on partly decomposed particles of organic waste), and parasites (feeding on tissues of living host).

Classification of Life's Diversity is organized in a Hierarchical Fashion.

• Kingdom
• Phylum (botanists use the term Division instead of Phylum)
• Class
• Order
• Family
• Genus
• Specific Epithet

A mnemonic device to help remember the order of the various taxonomic categories from the broadest to the most specific would be to memorize the following statement and let the letter of each word stand for the first letter of each category.  Ken's pants caught on fire, Great Scott!

This hiearchial system of classification to pigeonhole species is analogous to assigning a location where you might find an individual on the planet Earth.

Domain                                   Earth

Kingdom                           North America

Phylum or Division                 USA

Class                                   Arkansas

Order                             Craighead County

Family                              Jonesboro

Genus                           Fictitious Street

Specific Epithet                   1313

One final note about biological classification.  The focus of modern day classification schemes is an attempt to organize biological diversity according to evolutionary relationships that exist between species.  This is base on the premise that all life on this planet originated from one or a few ancestors which diverged over long periods of time to produce all the life forms we currently see on earth.  Taxonomy has given way to Systematics which attempts to reconstruct genealogical relationships among all life forms - for further information review Chapter 19 in the textbook.

• Kingdom Plantae
• Kingdom Fungi
• Kingdom Animalia

GENERAL INTRODUCTION TO PLANTS: IT'S NOT EASY BEING GREEN

Lecture Outline

1. Plants - common examples (e.g., duckweed, redwood tree, etc...) and biodiversity.
2. Characteristics of Plants.
3. Plant Reproduction (Asexual and Sexual Reproduction).
4. Role of plants in the biosphere.

1. Plants - Common examples and biodiversity.

The Kingdom Plantae includes a multitude of multicellular photosynthetic autotrophs (duckweed, geranium, apple tree, oak tree, dandelion, algae, red wood tree, carrot, etc.).  Lots of diversity! Plants come in different shapes, sizes. Some are short-lived, others live for hundreds of years. Plants have adapted to a wide variety of habitats, and methods of reproducing and dispersing themselves.

About 248,400 species of higher plants (i.e., ferns, gymnosperms, bryophytes, flowering plants). There are about 26,900 or more species of algae.

RELATED INTERNET LINKS:

• The Plant Kingdom (by Kornfeld)
• Classification of the Plant Kingdom (by Kornfeld)

2. Characteristics of plants

• Autotrophs - obtain energy/building materials by process known as photosynthesis.
• Sedentary (Plants don't move about, except through growth - although plants have evolved mechanisms to disperse their gametes, spores, and seeds).
• Modular construction - repeating units due to localized areas of growth (meristems - active regions of cell division); plants grow at the tips of shoots and roots (primary growth - occurring in all plants) and outward in girth (secondary growth - found in woody shrubs and trees, but not in herbaceous plants).
• Modules give the plant body form some measure of indeterminate growth.
• Different modules perform specific functions.
  • Roots - anchorage and absorption of water and dissolved nutrients.
  • Leaves - absorption of light energy and atmospheric gases (carbon dioxide).
  • Reproductive structures; male, female, or both sexes (e.g., flowers, cones).
  • Structures that hold spores or seeds as they mature (e.g., sporangia, cones, fruits).
  • Stem - support leaves and reproductive structures, and the link between these modules and the root system.
• Upper/lower surfaces of plants are generally highly branched. Maximize surface area for absorption of gas, light, nutrients and water.
• Cellular level (i.e., eukaryotes/multicellular, chloroplasts, cell walls, and large vacuoles).
• Plant Reproduction (Asexual and Sexual Reproduction).

TAKE HOME MESSAGE: Despite the differences between plant species, all plants share certain characteristics in common.

3. Plant Reproduction

• Asexual Reproduction or vegetative propagation: bulbs, corms, rhizomes, tubers, cuttings, grafting, plantlets, etc.
• Sexual Reproduction:  spores, seeds, etc. 

4. Role of plants in the biosphere.

How important are plants to other life forms on earth?

Beneficial Effects of Plants

1. Plants supply food.
2. Re-supply oxygen to atmosphere (without plants estimated 11 year supply on earth).
3. Plants help maintain the earth's livable climate (one reason why deforestation is of concern).

What kinds of plants/plant products have you come in contact with today?

Food, medicine, spices, fibers, paper, clothing, lumber, oxygen, fuel (coal and wood), toothpicks, toilet paper, paper money, soft drinks, drugs, etc.

Lecture Outline

1. Evolution of Fungi
2. Common Characteristics of Fungi
3. Human/Fungus Interactions

I.  Evolution of Fungi

The Kingdom Fungi is an ensemble of diverse species. Current evidence suggests that all fungal species are not derived from a single common ancestor (from within the Kingdom Protista), consequently the Fungi are polyphyletic (multiple genealogies or lineages).

RELATED INTERNET LINKS:

• THE KINGDOM FUNGI (by Kornfeld)
• TOM VOLK'S FUNGI

II. Common Characteristics of Fungi

1. Heterotrophy - 'other food'. There are three major categories of heterotrophs, which include the saprophytes, symbionts, and parasites.
   1. saprophytes (feed on dead tissues or organic waste)
   2. symbionts (mutually beneficial relationship between a fungus and another organism)
   3. parasites (feeding on living tissue of a host).  Parasites that cause disease are called pathogens.
2. Body form
   1. unicellular
   2. filamentous (tube-like strands called hypha [singular] or hyphae [plural]).
   3. mycelium = aggregate of hyphae.
   4. multicellular, such as rhizomorphs and fruit bodies (mushrooms)
3. Fungus is often hidden from view. It grows through its food source (substratum), excretes extracellular digestive enzymes, and absorbs dissolved food.
4. Indeterminate clonal growth.
5. Spores - asexual (product of mitosis) or sexual (product of meiosis) in origin.
   1. Purpose of Spores
      1. Allows the fungus to move to new food source.
      2. Resistant stage - allows fungus to survive periods of adversity.
      3. Means of introducing new genetic combinations into a population.
6. Vegetative phase of fungus is generally sedentary.
7. Cell wall present, composed of cellulose and/or chitin.
8. Food storage - generally in the form of lipids and glycogen.
9. Eukaryotes - true nucleus and other organelles present.
10. All fungi require water and oxygen (no obligate anaerobes).
11. Fungi grow in almost every habitat imaginable, as long as there is some type of organic matter present and the environment is not too extreme.
12. Diverse group, number of described species is 69,000 (estimated 1.5 million species total).

III.  Human/Fungus Interactions

     Beneficial Effects of Fungi

• Decomposition - nutrient and carbon recycling.
• Biosynthetic factories. Can be used to produce drugs, antibiotics, alcohol, acids, food (e.g., fermented products, mushrooms).
• Model organisms for biochemical and genetic studies.

     Harmful Effects of Fungi

• Destruction of food, lumber, paper, and cloth.
• Animal and human diseases, including allergies.
• Toxins produced by poisonous mushrooms and within food (e.g., grain, cheese, etc.).
  Plant diseases.

Lecture Outline

1. Evolution of Animals
2. The Animal Body - Invertebrates and Vertebrates
3. Tissues and Organs
4. Human Reproduction

I.  Evolution of Animals

Multicellular animals appear in the fossil record in rocks dated back to about 600 million years ago.  The Burgess Shale from Canada has provided a wealth of information, in addition to other sites, suggesting that animals representing most major phyla currently existing on earth and many others that went extinct underwent a "population" and "diversity" explosion during the Cambrian period (the "Cambrian Explosion"), during a relatively short period time in geological history - refer to Figure 23-2 on page 498 in the textbook.

II. The Animal Body - Invertebrates and Vertebrates

Strategies for making Heterotrophy in Animals Efficient

1. Multicellular animals have hierarchical construction
2. Organ Systems (Division of Labor)
   1. Muscle and Skeletal System (Movement and Support)
   2. Nervous System (To guide movement and coordinate responses)
   3. Sensory System (To detect food, water, mates, or danger)
   4. Excretory System (To get rid of bulk wastes)
   5. Immune System (To avoid infections caused by pathogenic bacteria, fungi, viruses, etc.)
   6. Circulatory System (To move food and oxygen through the body and remove carbon dioxide and other waste products)
   7. Respiratory System (To move oxygen into and carbon dioxide out of the body)
   8. Reproductive System (Allows for asexual and/or sexual reproduction;  all animals require some mode of reproduction to perpetuate themselves.  Many animal species are dioecious - "two houses",  that is, represented by male and female genders).
3. Compact Bodies (To efficiently contain various organs and organ systems)
4. Animals are divided into three major categories  - refer to Figures 23-4, 23-7, and 23-8 on pages 500-501 in the textbook.
   1. acoelomates - no body cavity
   2. coelomates - body cavity
   3. pseudocoelomates - false body cavity (formed without the mesodermal lining of a true coelom)

A.  Invertebrates (Animals without backbones)

Phylum: Porifera (sponges) - refer to Figure 23-9 on page 503 in the textbook.

Water, oxygen, and food particles enter through pores and exit through a larger opening called the osculum.  Sponges probably evolved independently from other animals, and in many ways are more similar to a colonial protist-like organism, composed of specialized cells that are interdependent on each other.  In fact, a mashed-up live sponge, passed through a mesh, will reform into new sponges.

• spicule (calcium and silicon crystals)
• amoebocytes - digest food and transfers nutrients
• epidermis (cells lining of various structures)
• choanocyte (collar cells) - move water with flagella and pass food to amoebocytes
• porocyte (pore cells) - openings which allow water to flow into the sponge.

Phylum:  Cnidaria (Hydra, jellyfish, corals, sea anemones - refer to Figures 23-10, 23-11, and 23-12 on pages 504-505 in the textbook)

All forms are aquatic or marine.  Two body forms exist within this group: a polyp (hydra-like or sea anemone-like) and medusa (jelly fish like).  Both forms may be sedentary or free floating.  These animals contain  a gastrovascular cavity with a single body opening, the mouth.  Tentacles are found near the entrance to the mouth.  These contain nematocysts (stinging cells) that are used to paralyze prey.

Phylum:  Platyhelminthes (flatworms, flukes, tapeworms - refer to Figures 23-14 and 23-15 on pages 507 and 508 in the textbook)

These animals exhibit bilateral symmetry and cephalization (organization of nervous and sensory systems towards one end of the body) is apparent.

Phylum:  Aschelminthes (roundworms, rotifers, nematodes, vinegar eels - refer to Figure 23-17on page 510 in the textbook)

Example of a an Aschelminthes species that causes a human diseases:  Trichinosis caused by Trichinella spiralis.  Parasite enters human body through infected undercooked pork.  Larvae carried by blood and lymph;  these bore through vessels into muscles and organs causing damage and pain.

Phylum Annelida (segmented worms - earthworms, leeches - refer to Figure 23-23 on page 516 in the textbook)

Bodies divided by a series of rings.

Phylum Arthropoda (insects, spiders, crabs, millipedes- refer to Figures 23-24, 23-25, and 23-26 on pages 518-520 in the textbook;)

Species diversity within this phylum is high, but most share several features in common:

• segmentation
• exoskeleton made of chitin
• jointed appendages

Phylum Mollusca (clams, snails, octopus, and squid - refer to Figures 23-18, 23-19, and 23-21 on pages 513-515 in the textbook)

No exoskeleton, but some forms surrounded by a hard shell.

Phylum Echinodermata (starfishes, sea urchins, sea cucumbers - refer to Figures 24-3 and 24-4 on pages 504-505 in the textbook;)

Found in marine environments; animals exhibit radial symmetry;  Water vascular system in starfish used to move food and gases into the body, and create suction in the suction cup like "feet" so animals can cling to rocks and gather food (e.g., opening up clams).

B.  Vertebrates (animals with backbones - refer to Figure 24-7 on page 529 in the textbook)

Phylum Chordata (fish, amphibians, reptiles, mammals, birds, etc. - refer to Figures 24-9 through 24-23 on pages 530-541 in the textbook;)

• dorsal notochord (running down the back of the animal)
• subphylum Vertebrata (notochord replaced by a hard backbone)
• dorsal nerve cord
• gills or gill-like structures found during some point in the life cycle

Class "The Fishes" (e.g., lampreys, cartilaginous fish, bony fish)

Class Amphibia (e.g., frogs, salamanders)

• semi-terrestrial
• young have gills
• lay eggs in water
• skin is moist

Class Reptilia (e.g., snakes, turtles, lizards)

• scales on skin which prevent drying out
• eggs laid on land or capable of live birth

Class Aves (birds)

• feathers (modified reptilian scales)
• many species capable of flight

Class Mammalia (e.g., horses, mice, dolphins, cats, humans, etc.)

• mammary gland (offspring fed milk)
• hair and fur (modified reptilian scales) - warmth

Take-home message:  As various groups of animals adapted to new and changing environments and diversified, new organ systems evolved.  These different organ systems make possible the various forms of animal life observed on earth today and those specimens represented in the fossil record.

Various morphological, embryological, geological (fossil record) and molecular genetics data have been used to develop evolutionary trees or phylogenies to reconstruct genealogical relationships among existing phyla of animals.  These vary depending on the data use in the analysis, although some consensus does exist.

RELATED INTERNET LINKS:

• THE ANIMAL KINGDOM (by Kornfeld)

I. Animal Tissues and Organs

• Tissue:  similar cells performing an identical function (muscles; contraction; blood; oxygen transport).
• Organ:  groups of different tissues performing a distinct function (eye: sight; brain: coordinates and processes nerve impulses)

Some major animal tissue types

• Muscle: movement, posture, beating of heart
  • smooth - involuntary
  • striated
    • skeletal: voluntary
    • cardiac: involuntary
• Epithelial - cells that cover organs and other structures
• Connective (bones, cartilage, blood, lymph)
  • support
  • transport of nutrients, energy, oxygen to tissue removal of carbon dioxide and waste products from tissues
    • plasma
    • corpuscles
      • red blood cells (erythrocytes) - movement of gases
      • white blood cells (leukocytes) - removal of infectious agents through phagocytosis
      • platelets (blood clotting)
• Nerve tissue - transmission and coordination of nerve impulses

Given time constraints, further discussion about organs (such as the eye - see Figure 42-9 on page 873 in the textbook) and organ systems will not be discussed in further detail with the exception of the human reproductive system.  The notes and discussion follows:

II.  Human Reproduction - refer to text and figures found in Chapter 43 in the textbook.

The nuclei in most human cells are diploid ==> 46 chromosomes:  22 pairs of homologous or autosomal chromosomes and 1 pair of sex chromosomes.

Gametogenesis - formation of haploid (23 chromosomes) gametes is the result of meiosis, cytokinesis, and cellular differentiation, which occurs in the gonads.

• Male gonads = testes
  • Gametogenesis that gives rise to male gametes is called spermatogenesis
  • Male gametes are called sperm
  • Spermatogenesis starts in human males at the onset of puberty (age 12-13) and continues through the life of the adult
• Female gonads = ovaries
  • Gametogenesis that gives rise to female gametes (one large ovum and three polar bodies) is called oogenesis
  • Female gametes are called eggs or ova (sing. ovum) or oocytes (prior to release from the follicle).
  • Oogenesis begins prior to birth, but cells destined potentially to become eggs, undergo meiotic arrest during Metaphase I and stay in stasis until the onset of puberty (age 12-13), and dispensed once every 28 days from puberty (age 12-13) through menopause (age 50)

Hormonal Control of Human Reproduction

A "releasing hormone" is produced by the hypothalamus (in the brain) causes the anterior pituitary gland to secrete luteinizing hormone (LH) and foollicle-stimulating hormone (FSH).  These two hormones travel through the blood stream and migrate to the gonads.

• FSH=>stimulates gametogenesis and maturation of gametes
• LH=>stimulates accessory cells to produce sex steroids (all three produced in males and female but in different concentrations
  • (1) testosterone, (2) estrogen, and (3) progesterone
  • Responsible for secondary sexual characteristics
    • In females==>breast tissue proliferation, deposition of fat deposits
    • In males==>voce quality, facial and pubic hair growth, muscle and bone development, and sex drive

Human Reproductive Structures and Function

Male Reproductive Organs and Function

Testes are found outside the abdominal cavity in a sac (scrotum).  Viable sperm are produced at a temperature lower than the human body temperature (98.6 degrees F or 37 degrees C). Within a testis are the seminiferous tubules (80% of testicular mass) and represents the location of spermatogenesis.  Sperm enter a coiled tubule called the epididymis (found outside the testis).  It takes about 10-12 days for sperm to mature and gain the ability to swim.  Sperm exit the epididymis via the vas deferens; a duct that loops up behind the bladder in the abdominal cavity and connects to the urethra.  The urethera passes through the penis.  During intense sexual arousal, blood fills blood vessels within the penis to generate an erection.  Sperm mixes with glandular secretions to produce the semen.  Semen is ejected by rhythmic contractions and leads to ejaculation. Orgasm involves ejaculation, increases in blood pressure and heart rate, skeletal muscles tense then relax, followed by mental relaxation and sensations of pleasure.  A refractory period during which time a second orgasm is not possible follows.

Female Reproductive Organs and Function

The ovaries are the site of oogenesis (egg formation) and found within the abdominal body cavity.  The uterus or womb is the location where the embryo implants and develops during pregnancy. Oviducts = Fallopian Tubes are necessary so the egg can travel from the ovary to the uterus.  The vagina is opening of the body that leads to the uterus and serves as the entry point for sperm and exit point for the offspring at the end of pregnancy.  Sexual union or copulation allows the semen containing sperm to enter the uterus and make its way to the egg, where fertilization is a possible outcome. Orgasm in the female leads to rhythmic contractions of the uterine muscle which may assist sperm in their journey to the egg.

The ovary contains follicles (sac-like structures each containing one oocyte).  Female gametes mature in a monthly cycle (approx. 28 days) called the menstrual cycle.  Menstruation = 3-7 day period of blood discharge from the uterus.  This bloody discharge represents the removal of the endometrium.  During the course of the menstrual cycle, hormone levels rise and fall.  Low levels of estrogen inhibits the release of LH and FSH, while high levels of estrogen increase the release of LH and FSH in the pituitary gland.  Ovulation occurs, the egg is released starting its journey to the Fallopian tubes.  The used or spent follicles fill with cells and form the corpus luteum, causing progesterone levels to rise.  The increased levels of progesterone prevents additional ovulation and helps the endometrium to remain thick.

Fertilization and Pregnancy

One sperm unites with an egg and leads to fertilization.  The fertilized egg becomes the zygote.  Due to the union of the contents of two haploid nuclei from the sperm and the egg, and the cytoplasm components of the egg, the zygote is diploid (23 pairs of chromosomes in the nucleus; maternal inheritance of the organelles/cytoplasm - e.g., mitochondria).  The zygote undergoes cell division and a blastula (ball of cells) develops.  As the cells differentiate, different tissues form in the embryo.  Within 7 days, the embryo reaches the uterine cavity and implants.  The placenta forms providing the embryo with oxygen and food, and generates more progesterone, which inhibits menstruation (which would result in a miscarriage). Gestation in humans takes 38-40 weeks; approx. 9 months after which a baby is born.

Potential consequences of sexual intercourse

• production of children
• emotional reinforcement of pair-bonding between consenting adults
• potential spread of sexually-transmitted diseases (CHAPTER 43)

The following information is lacking in your textbook, but information that is appropriate in the context of human sexual biology and behavior.
 

ECOSYSTEMS AND ENERGY FLOW - refer to text and figures in Chaper 25 found in the textbook.  Discussion in lecture as time allows.

FINAL TOPIC:  HUMAN IMPACT ON THE ENVIRONMENT - refer to text and figures in Chaper 28 found in the textbook.  Discussion in lecture as time allows.

• Human population growth
• deforestation
• air pollution (CFC's, greenhouse gases, ozone layer loss)
• water pollution (industrial waste, petroleum, agrochemical  runoff)
• solid waste and land-fills
• urban sprawl and land use
• greenhouse effect and global warming
• conventional and nuclear war
• decline in biodiversity and collapsing of ecosystems/biomes

This page was assembled by Martin J. Huss, who can be reached at mhuss@astate.edu.
Last revised on: December 7, 2004.