When an insect group specializes on a particular family that's toxic to others, it suffers little competition for that resource.

Mimicry of toxic animals by non-toxic animals also has evolved as a result of such specialization on poisonous plant families. (e.g., the Monarch Butterfly and its harmless Viceroy mimic)

Numerous alkaloids have evolved to deter herbivores. But it's That Amazing Primate who just doesn't seem to get the message who always seems able to subvert evolution and turn it to His/Her own purposes.

Angiosperms have a greater variety of complex secondary metabolites than any other type of organism, and it has been these, in part, that have spurred the success of this group, along with the flower and fruit.

Ethnobotany is a field within the biological sciences that bridges across to anthropology. It is the study of the use of indigenous plants by indigenous human cultures, Particular interest often lies in the discovery of how plants and plant compounds are used in medicinal and religious practice, as these can have commercial application.

Ecological Succession

Every species has a set of environmental conditions under which it will grow and reproduce optimally. In a given ecosystem, and under that ecosystem's set of environmental conditions, those species that can grow the most efficiently and produce the most viable offspring will become the most abundant organisms. As long as the ecosystem's set of environmental conditions remains constant, those species optimally adapted to those conditions will flourish.

The "engine" of succession, the cause of ecosystem change, is the impact of established species have upon their own environments. A consequence of living is the sometimes subtle and sometimes overt alteration of one's own environment. The original environment may have been optimal for the first species of plant or animal, but the newly altered environment is often optimal for some other species of plant or animal. Under the changed conditions of the environment, the previously dominant species may fail and another species may become ascendant.

Ecological succession may also occur when the conditions of an environment suddenly and drastically change. A forest fires, wind storms, and human activities like agriculture all greatly alter the conditions of an environment. These massive forces may also destroy species and thus alter the dynamics of the ecological community triggering a scramble for dominance among the species still present.

Sample diagram of ecological succession. Pioneer species include a variety of annual plants. This successional stage is then followed by communities of perennials and grasses, shrubs, softwood trees and shrubs, and finally hardwood trees and shrubs. This succession takes about 120 years to go from the pioneer stage to the climax community in a typical North American deciduous forest community.

Definition of a virgin forest is...

Biomes: How Plants Affect the Structure of Major Ecosystems

Major Terrestrial Biomes

• Arctic Region at the north and south poles
  • Located above 60^o North and South latitudes
  • Arid (for the reasons described in the section on climate)
  • Bitterly cold temperatures
  • Day length varies tremendously, with 24 hour daylight or night at the respective solstices.
  • Low animal diversity
  • Most photosynthetic organisms are marine, and most sun energy is captured in the water.
  • Some typical vertebrates you might find here: penguins (Antarctic only; no penguins in the North), seals, walruses, whales of various species, polar bear.
  • Typical plants: Not much here but some diatoms in the ocean and ice, and possibly some floating algae.

• Tundra. See more beautiful images of the tundra.
  • Located just south of the polar regions in the northern hemisphere.
  • Arid (as are the polar regions)
  • Characterized by PERMAFROST: a permanently frozen layer of soil, which may be deeper in summer than in winter, but still prevents the growth of large trees with deep root systems.
  • most plants are scrubby and small
  • lichens (fungus/algae symbiosis) are a major photosynthetic food source
  • High winds and cold temperatures prevail
  • Very short days in winter, very long days in summer
  • Typical vertebrates: reindeer/caribou, Snowy Owls, Grizzly Bear, Brown Bear, Wolf, Arctic Fox, Ptarmigan (a partridge-like bird), migratory birds, lemmings (small rodents), voles (another rodent).
  • Typical Plants: Small, shrubby perennials; profusion of flowering annuals visible in the spring and summer; small trees with shallow roots due to permafrost. Lichen, a symbiotic relationship between fungus and a protist or bacterial autotroph, is one of the major primary producers in the arctic tundra, and a vital source of food for the tundra's herbivores.

• Coniferous (Boreal) Forest (also known as "taiga") . See more images of the taiga/boreal forest.
  • Found south of the arctic and tundra regions, primarily in the northern hemisphere
  • Northern boreal forest receives tremendous snowfall in winter; the conical shape of pines may help them shed snow and avoid damage to their branches from the weight of snow.
  • Highly endangered, these ecosystems are being rapidly logged out, especially in North America.
  • Also found along the the Andes of South America
  • Major plant form: evergreen, coniferous trees such as pines, firs, spruce, etc. (Cone-bearing trees). Under the trees grow shrubs, mosses, ferns, etc.
  • Relatively high levels of rainfall, but short days in the winter.
  • Typical vertebrates: deer, wolf, bear, foxes, many migratory birds, squirrels, rabbits, etc. Higher species diversity than tundra.

• Temperate Deciduous Forest
  • Found south of the coniferous forest in areas of relatively high rainfall and relatively high elevation, but with longer day length than in coniferous regions
  • Major plant form: deciduous (i.e., trees that seasonally drop their leaves) flowering trees and shrubs.
  • Typical temperate deciduous forest areas are the northeastern U.S. and most of Europe.
  • Typical vertebrates: deer, wolf, bear, foxes, many migratory birds, squirrels, rabbits, etc. Somewhat higher species diversity than coniferous forest. Some species hibernate through the winter, when food is scarce in the snowy landscape.

• Prairie (Temperate Grassland) and more beautiful shots of Prairie can be seen HERE.
  • Characterized by distinct seasonal changes, moderate rainfall, extremely rich, organic soil.
  • Major plant forms: annual grasses and flowering plants; some areas with more standing water become marshes characterized by small trees such as willows, cottonwoods, etc.
  • Very fertile land, but with harsh seasonal variations: hot summers, cold winters
  • The "veldt" of South Africa, the "puszta" of Hungary, the "pampas" of Argentina, the steppes of Central Asia and Russia, and the plains of the central U.S. are all examples of this highly productive biome.
  • Most of these grasslands have been converted to farmland for human use, but some native grasslands have been preserved.
  • Typical vertebrates: American Bison (sometimes erroneously called "buffalo"), prairie dog, jackrabbit, fox, coyote, deer, many migratory birds (especially predatory birds such as hawks and falcons), etc. Many animals undergo winter hibernation.

• Savanna (Tropical/Subtropical Grassland)
  • Characterized by distinct seasonal changes, highly seasonal rainfall (very harsh dry season), extremely rich, organic soil.
  • Major plant forms: annual grasses and flowering plants; Trees are generally very drought tolerant and have high canopies due to herbivory by large animals such as elephants and giraffes.
  • Fire is a major abiotic component of this biome, and most plant species are evolved to withstand periodic fires
  • Very fertile land, but with harsh seasonal variations: very wet season followed by extremely harsh dry season (during which most animals migrate away)
  • Lush grass and shrubbery growth in the rainy season provides ample food for large animals, but they must migrate to greener pastures during drought.
  • Typical vertebrates: grazing hoofed mammals (gazelles, antelopes, etc.), lions, leopards, cheetahs, elephants, giraffes, true buffalo (Water Buffalo, Cape Buffalo), rhino, hippopotamus, etc.

• Chaparral (Mediterranean Scrub Forest)
  • Found in arid regions with Mediterranean climate (e.g., southern California, Spain, European and African areas bordering the Mediterranean Sea; southern tip of Africa, southwestern tip of Australia)
  • Winters are rainy and mild; summer days are long, hot, and very dry
  • Characterized by periodic, seasonal fires
  • Major plant forms: Dense, spiny, evergreen shrubs (some of these produce seeds that will germinate and grow only after they've been through a fire.)
  • Typical vertebrates: coyote, mule deer, various rodents, many lizards, snakes, migratory birds, etc.

• Tropical Rainforest
  • Found worldwide (at least in times past) around the equator
  • Extremely high levels of rainfall
  • Poor nutrient content in soils due to high levels of rainfall
  • Tremendous plant diversity; large trees have shallow root systems evolved to be able to quickly absorb nutrients as soon as they become available (due to decay of dead things), before the rains wash them away.
  • Very dense plant growth and very high level of productivity
  • In mature rainforest, the forest floor is relatively clear of plants, since the upper canopy of trees blocks most sunlight. Only when there's a large treefall does a new growth of shrubby "pioneer species" germinate from the soil and provide cover for the forest to re-grow.
  • Typical vertebrates: You name it! More than 50% of all the earth's terrestrial animal species are found in the tropical rainforest. Picture: monkeys, toucans, parrots, reptiles of all types, amphibians, and representatives of just about any major animal group.

• Desert (plus a view of Joshua Tree National Monument and Death Valley National Park.
  • Extremely arid. Very hot in the daytime; in some regions, extremely cold at night
  • High nutrient levels in the soil due to very little rainfall
  • Sparse plant life due to very low humidity and available water
  • Plantlife is XERIPHYTIC (from the Greek xeri, meaning "dry" and phyt meaning "plant"): evolved to have special adaptations to store and avoid losing water.
  • typical plants: cactus, Yucca, xeriphytic shrubs of various species, spectacular explosion of flowering annuals comes with the spring rains
  • typical vertebrates: drought-tolerant mammals such as desert foxes, burros, jackrabbits, high diversity of snakes and lizards, tortoises, Roadrunner and some other desert-adapted birds (plenty of hawks and eagles)

  Recall the link between soil nutrient content and precipitation.

• Which of these biomes has the highest productivity?
• Which has the highest and lowest soil nutrient content?
• Which are most useful to humans for agriculture?

  ---

  ---