1. The Burgess Shale is a rock outcropping in Yoho National Park, British Columbia discovered by Charles Doolittle Walcott in 1909.
2. In this area there is a large quantity of fossils.
3. At the beginning of the excavation, it was difficult to extract the fossils from their matix, but now new methods that involve UV light and diluted acetic acid make it easy to free the fossils.
4. These marine fossils are thought to have lived around 540 million years ago (MYA), during the Precambrian period.
5. Many fossils found in the Burgess Shale are soft-bodied invertebrates, which is unusual since soft-bodied animals rarely fossilized.
6. When these organisms were alive, they all lived in the sea, and this area was subjected to mudslides. The mud entered the sea, buried the animals. Later the mud turned into shale and over time the shale was raised. Mud particles filled the spaces around the organisms, so the soft tissue was preserved and fossils became somewhat three-dimensional.
7. Organisms that have been preserved at the Burgess Shale are vertebrates, invertebrates, and unicellular organisms.
8. There is much dispute regarding the evolution of these species. Some scientist believe that evolution of these species happened slowly, while others believed it happened quickly and suddenly.
1. The Earth came into being about 4.6 BYA (BYA).
2. Heat from gravitation and radioactivity formed the Earth in several layers with iron and nickel in a liquid core, silicate minerals in a semi-liquid mantle, and upwellings of volcanic lava forming the first crust.
3. The Earth's mass provides a gravitational field strong enough to hold an atmosphere.
4. Early Earth's atmosphere differed from the current atmosphere, consisting of:
a. water vapor,
c. carbon dioxide,
d. small amounts of hydrogen, methane, ammonia, hydrogen sulfide, and carbon monoxide.
5. The early atmosphere was formed by volcanic out-gassing characteristic of the young Earth.
6. The early atmosphere contained little free oxygen (O2) and was probably a reducing atmosphere with little free oxygen; a reducing atmosphere lacks free O2 and allows formation of complex organic molecules.
7. The early Earth was so hot that H2O only existed as a vapor in dense, thick clouds.
8. As the Earth cooled, H2O vapor condensed to form liquid H2O, and rain collected in oceans.
9. The Earth's distance from the sun allows H2O to exist in all phases: solid, liquid, and gas.
10. NASA photos seem to confirm that Earth is bombarded by comets adding substantial water vapor.
The Mesozoic Era
1. Although there was a mass extinction at the end of the Paleozoic, evolution of some plants and animals continued into the Triassic, the first period of the Mesozoic Era.
2. The Triassic period
a. Gymnosperms flourished, especially cycads; the Triassic and Jurassic are called the "Age of Cycads."
b. One group of reptiles, the therapsids, had the first mammal features.
c. Reptiles, originating in the Permian, underwent adaptive radiation.
3. The Jurassic Period
a. Many dinosaurs flourished in the sea, on land and in air.
b. Controversy surrounds dinosaurs being ectothermic or endothermic.
4. The Cretaceous Period
a. A new Chinese fossil, Jeholodens, reveals an early mammal with a long snout but sprawling reptile-like hind limbs.
b. The era of dinosaurs ended in a mass extinction in which dinosaurs, most reptiles, and many marine organisms perished.
1. Aristotle classified life into 14 groups (e.g., mammals, birds, etc.), and subdivided them by size.
2. Ray grouped animals and plants according to how he thought they were related.
3. Linnaeus grouped plants by flower parts; his categories were published in Systema Naturae in 1735
4. Today, taxonomists use seven categories of classification: species, genus, family, order, class, phylum, and kingdom.
a. A higher category, the domain, has recently been added to these seven categories.
b. The higher the category, the more inclusive it is.
c. Members of a kingdom share general characters; members of a species share quite specific characters.
d. Since one taxonomic group exists inside another group, these categories are also termed nested.
A character is any structural, chromosomal, or molecular feature that distinguishes one group from another.
e. Additional levels of classification can be added by adding super , sub , or infra (e.g., suborder); thus, there are more than 30 categories of classification.
a. Most free living bacteria are chemoheterotrophs that take in pre-formed organic nutrients.
b. As aerobic saprotrophs, there is probably no natural organic molecule that cannot be broken down by some prokaryotic species.
c. Bacteria produce chemicals including ethyl alcohol, acetic acid, butyl alcohol, and acetones.
d. Bacteria action produces butter, cheese, sauerkraut, rubber, cotton, silk, coffee and cocoa.
e. Antibiotics are produced by some bacteria.
1. Cyanobacteria are Gram negative bacteria with a number of unusual traits.
2. They photosynthesize in the same manner as plants, and thus are responsible for introducing O2 into the primitive atmosphere.
3. They were formerly mistaken for eukaryotes and classified with algae.
4. Cyanobacteria have pigments that mask chlorophyll; they are not only blue green but also red, yellow, brown, or black.
5. They are relatively large (1-50 µm in width).
6. They can be unicellular, colonial, or filamentous.
7. Some move by gliding or oscillating.
8. Some possess heterocysts, thick walled cells without a nucleoid, where nitrogen fixation occurs.
9. Cyanobacteria are common in fresh water, soil, on moist surfaces, and in harsh habitats (e.g., hot springs).
10. Some species are symbiotic with other organisms (e.g., liverworts, ferns, and corals).
11. Lichens are a symbiotic relationship where the cyanobacteria provide organic nutrients to the fungus and the fungus protects and supplies inorganic nutrients.
12. Cyanobacteria were probably the first colonizers of land during evolution.
13. Cyanobacteria "bloom" when nitrates and phosphates are released as wastes into water; when they die off, decomposing bacteria use up the oxygen and cause fish kills.
At some time during their life, all chordates have four basic characteristics.
1) This supporting rod is located dorsally just below the nerve cord.
2) It provides support and is replaced by the vertebral column in vertebrates.
b. Dorsal Tubular Nerve Cord
1) This cord contains a fluid filled canal.
2) In vertebrates, this is the spinal cord and it is protected by vertebrae.
c. Pharyngeal Pouches
1) These openings function in feeding, gas exchange, or both.
2) They are seen only during embryonic development in most vertebrates.
3) In invertebrate chordates, fish, and amphibian larvae, they become functioning gills.
4) In terrestrial vertebrates, the pouches are modified for various purposes.
5) In humans, the first pair of pouches become the auditory tubes, the second become tonsils, and the third and fourth pairs become the thymus and parathyroid glands.
d. A postanal tail extends beyond the anus; in some, this only appear in embryos.
c. A survivorship curve, obtained by plotting the number of individuals surviving at each age, is characteristic of each species.
1) In the Type I survivorship curve, most individuals live out their life span and die of old age (e.g., humans in well-developed countries).
2) In the Type II survivorship curve, individuals die at a constant rate across their lifespan (e.g., birds, rodents, and perennial plants).
3) In the Type III survivorship curve, most individuals die early in life (e.g., fishes, invertebrates, and plants).
When a Population Grows Too Large (Ecology focus box)
1. About 100 years ago the white-tailed deer population across the eastern United States was less than 500,000, and now, it is over 200 million deer.
2. The increase in population size can be attributed to the lack of predators.
a. Hunting is tightly controlled, or banned altogether.
b. Natural predators such as wolves and mountain lions are absent from most regions.
3. In areas where the deer populations have become too large, the deer suffer from starvation as they deplete their own food supply.
4. The large deer population also causes economic loss due to loss of agriculture, forestry, and even insurance claims due to deer-vehicle collisions.
5. Deer overpopulation also harms other species.
a. In areas where there are many deer, there are fewer understory plants.
b. The number of songbirds, insects, squirrels, mice, and other animals declines with an increasing deer population.
6. Some states are working on effective deer management plans.
a. Texas landowners can set aside a portion of their property for a deer herd, and in return, can charge people for the opportunity to hunt on their land.
More Developed Versus Less Developed Countries
1. The more developed countries underwent a demographic transition from 1950-1975; their growth rate is now low.
a. The more developed countries (MDCs) (e.g., Europe, North America, Japan, etc.) have low population growth and people enjoy a good standard of living.
b. Less developed countries (LDCs) (e.g., countries in Africa, Asia, and Latin America) are those in which population growth is expanding rapidly and the majority of people live in poverty.
c. LDC growth rate peaked at 2.5% between 1960-1965; it has been declining slowly to about 1.6%.
d. Demographic transition is a decline in death rate followed by declining birthrate; it results in slower growth, about 0.1%.
2. The less developed countries (LDCs) are now undergoing demographic transition.
3. Most of the explosive growth will occur in Africa, Asia and Latin America unless
a. family planning or birth control are strengthened,
b. the desire for more children is reduced, and
c. the onset of childbearing is delayed.
The Carbon Cycle
1. Both terrestrial and aquatic organisms exchange carbon dioxide with the atmosphere—this is called the carbon cycle.
2. On land, photosynthesis removes CO2 from the atmosphere; respiration then returns CO2 to the atmosphere.
3. CO2 from the air combines with water to produce bicarbonate (HCO3), which is a source of carbon for aquatic producers, primarily protists.
4. Similarly, when aquatic organisms respire, the CO2 they release combines with water to form bicarbonate ions (HCO3-).
5. The reservoir for the carbon cycle is largely composed of organic matter, calcium carbonate in shells, and limestone, as well as fossil fuels.
6. The transfer rates between photosynthesis and respiration (including decay) are about even.
7. Because we burn fossil fuels and forests, there is now more CO2 entering the atmosphere than is removed.
8. CO2, nitrous oxide, and methane are greenhouse gases that contribute to the rise in Earth's temperature, a phenomenon called global warming.
9. The above gases and water vapor increase the greenhouse effect that holds heat next to the Earth.
10. The increased heat may cause more clouds that in turn increase global warming.
11. Computer models cannot incorporate all variables; predictions are for 1.5-4.5oC increase by 2100.
12. Possible results may include glaciers melting, sea levels rising, a redistribution of dry and wet regions, and an increase in species extinctions.
In the 1980s, scientists became concerned that ozone depletion was occurring world-wide and most serious above the Antarctic every spring.
a. Ozone holes have also been detected above the Arctic, and within northern and southern latitudes, where many people live.
4. The cause of ozone depletion was found to be chlorine atoms (Cl), which can destroy up to 100,000 molecules of ozone before settling back to the Earth's surface.
5. Chlorine atoms entered the stratosphere from the breakdown of chlorofluorocarbons (CFCs)
a. The best-known CFC is Freon, which is a coolant found in refrigerators and air conditioners.
b. CFCs are also used in cleaning agents and in styrafoam inflation, insulation, and paddings.
6. The United States stopped the production of CFCs in 1995, and since then the amount of Clorine atoms in the stratosphere has started to decline.
7. However, currently there are more polar clouds (which contribute to ozone depletion) than previously thought.
a. As the surface of the Earth warms, due to global warming, less heat reradiates into the stratosphere.
b. It is speculated that once polar stratospheric clouds become twice as persistent, there could still be an ozone loss of 30%.
1. The Arctic tundra encircles the Earth south of the ice-covered polar seas in the Northern Hemisphere.
2. Arctic tundra covers 20% of the Earth's land surface; it is cold and dark much of the year.
3. The tundra receives about 20 cm of rainfall annually; this would constitute a desert but the melting snow provides water during summer and very little evaporates.
4. Only the topmost layer of Earth thaws; the permafrost beneath is always frozen.
5. Trees are not found in the tundra because
a. the growing season is too short,
b. their roots cannot penetrate the permafrost, and
c. trees cannot become anchored in the boggy soil of summer.
6. In the summer, the ground is covered with sedges and short-grasses with patches of lichens and mosses.
7. Dwarf woody shrubs flower and seed quickly while there is sunlight for photosynthesis.
8. Only a few animals adapted to cold live in the tundra year-round (e.g., lemming, ptarmigan, and musk-ox).
9. During the summer, the tundra contains many insects, birds, and migratory animals (e.g., shore birds, waterfowl, caribou, reindeer, and wolves).
1. Conifer forests are found in three locations: taiga, montane coniferous forests, and temperate coniferous forests.
2. Taiga is coniferous forest extending across northern Eurasia and North America.
3. Near a mountain top is a similar conifer forest called a montane coniferous forest.
4. On the Pacific Coast from Canada down to California is part of the temperate rain forest.
5. Conifer forests contain great stands of spruce, fir, hemlock, and pine; these trees have thick protective leaves or needles and bark.
6. The needlelike leaves can withstand the heavy weight of snow.
7. There is a limited understory of plants; the floor is covered by low-lying mosses and lichens beneath the layer of needles.
8. Birds harvest the seeds of conifers; bears, deer, moose, beaver and muskrat live around the cool lakes and streams.
9. Major carnivores include wolves, wolverines, and mountain lions.
10. The temperate rain forest along the Pacific Coast has the largest trees in existence, some as old as 800 years.
D. Temperate Deciduous Forests
1. Temperate deciduous forests are found south of the taiga in eastern North America, eastern Asia, and much of Europe.
2. Climate in these areas is moderate with a relatively high annual rainfall (75-150 cm).
3. The seasons are well-defined with a growing season that ranges between 140 and 300 days.
4. The trees of a deciduous forest (e.g., oak, beech, and maple) have broad leaves which they lose in the fall and grow again in the spring.
5. Enough sunlight penetrates the canopy to support a well-developed understory composed of shrubs, a layer of herbaceous plants, and a ground cover of mosses and ferns.
6. Stratification beneath the canopy provides a variety of habitats for insects and birds.
7. Deciduous forest contains many rodents that provide food for bobcats, wolves, and foxes.
8. Deciduous forest also contains deer and black bears.
9. Compared to the taiga, the winters are milder and allow many amphibians and reptiles to survive.
10. Minerals are washed into the ground and eventually brought back up by deep roots of trees.
1. Tropical rain forests are found in South America, Africa, and the Indo-Malayan region near the equator.
2. The climate is warm (20o-25o C) and rainfall is plentiful with a minimum of 190 cm per year.
3. This is probably the richest biome, both in number of species and in their abundance.
4. A tropical rain forest has a complex structure, with many levels of life.
5. Although there is animal life on the ground (e.g., pacas, agoutis, peccaries, and armadillos), most of the animals live in the trees.
6. Insects are abundant in tropical rain forests; the majority have not been identified.
7. Termites are critical in the decomposition of woody plant material.
8. Various birds tend to be brightly colored.
9. Amphibians and reptiles are represented by many species of frogs, snakes, and lizards.
10. Lemurs, sloths and monkeys feed on fruits.
11. The largest carnivores are cats (e.g., jaguars in South America and leopards in Africa and Asia).
12. Epiphytes are air plants that grow on other plants.
a. They have roots of their own to absorb moisture and minerals leached from the canopy.
b. Others catch rain and debris in hollows of overlapping leaf bases.
c. Common epiphytes are related to pineapples, orchids and ferns.
13. Tropical forests in India, Southeast Asia, West Africa, West Indies, and Central and South America are seasonal.
a. They have deciduous trees that shed leaves in the dry season; layers of undergrowth are below.
b. Certain of these forests contain elephants, tigers and hippopotami.
14. A year-long growing season and high temperatures mean productivity is high.
15. But the warm, moist climate that supports high productivity also promotes rapid recycling of litter.
16. The soil is called laterite and the iron and aluminum oxides give it a red color and a brick texture when it bakes in the hot sun.
17. Consequently the soil is relatively poor because the nutrients are rapidly cycled into the biomass; this makes a poor agricultural soil.
Grasslands occur where rainfall is greater than 25 cm but is insufficient to support trees.
2. In temperate areas with rainfall between 10 and 30 inches a year, grassland is the climax community; it is too wet for desert and too dry for forests.
3. Natural grasslands once covered over 40% of the Earth's land surface.
4. Most grasslands now grow crops, especially wheat and corn.
5. Grasses generally grow in different seasons; therefore some grassland animals migrate and ground squirrels hibernate when there is little grass.
6. The temperate grasslands include the Russian steppes, South American pampas, and North American prairies.
7. Tall-grass prairie occurs where moisture is not sufficient to support trees.
8. Short-grass prairie survives on less moisture and is between a tall-grass prairie and desert.
9. Animal life includes mice, prairie dogs, and rabbits and the animals that feed on them: hawks, snakes, badgers, coyotes, and foxes.
10. Prairies once contained large herds of buffalo and pronghorn antelope.
Savannas are tropical grasslands that contain some trees.
a. The savanna occurs in regions where a relatively cool dry season is followed by a hot, rainy one.
b. The savanna contains the greatest variety and numbers of herbivores (e.g., antelopes, zebras, wildebeests, water buffalo, rhinoceroses, elephants, and giraffes).
c. Any plant litter not consumed by grazers is attacked by termites and other decomposers.
d. Termites also build towering nests and tend fungal gardens.
e. The savanna supports a large population of carnivores (e.g., lions, cheetahs, hyenas, and leopards).
El Niño-Southern Oscillation (Ecology focus box)
1. El Niño-Southern Oscillation (ENSO) refers to a sever weather change brought on by an interaction between the atmosphere and the ocean currents.
2. Ordinarily, the southeast trade winds move along the coast of South America and turn east because of the Earth's daily rotation on its axis.
a. The winds bring warm ocean waters from east to west.
b. There is also an upwelling of nutrient-rich cold water from the depths of the ocean, resulting in a large Peruvian harvest of anchovies.
c. The warm ocean waters also bring monsoon rain to India and Indonesia.
3. During an El Niño, the northeast and southeast trade winds slacken.
a. There is no upwelling, and anchovy harvest plummets.
b. Waters from the east may never reach the west.
c. Winds lose moisture in the middle of the Pacific, rather than the Indian Ocean.
d. Drought occurs in India, Indonesia, Africa, and Australia.
4. Some parts of the United States benefit from an El Niño.
a. The Northeast is warmer than usual.
b. Fewer hurricanes hit the east coast.
c. Tornadoes decrease in the Midwest.
5. Following El Niño, normal conditions occur, which is known as La Niña.
6. As climate changes, the severity of El Niños remains somewhat unpredictable.