Chapter 10: Cycles and Patterns in the Biosphere – p. 1 of 7

Chapter 10: Cycles and Patterns in the Biosphere

  1. The Impact of Plants and Animals on the Landscape
  2. The Geographic Approach to the Study of Organisms
  1. geographic viewpoint:
  1. seeks generalizations and patterns
  2. interested in distribution and relationships
  3. biogeography: study of the distribution patterns of plants and animals and how these patterns change over time
  1. The Search for a Meaningful Classification
  2. Seeking Pertinent Patterns
  1. about 600,000 plant species; twice as many animal species
  2. biota: total complex of plant and animal life
  1. flora: plants
  2. fauna: animals
  1. Biogeochemical Cycles
  1. Earth’s atmosphere and hydrosphere have been composed of approximately the same balance of chemical components for the last billion years
  2. The Flow of Energy
  1. sun is the basic energy source on which nearly all life ultimately depends

a.~ 0.1% of solar energy that reaches Earth is fixed in photosynthesis

b.> ½ of that total is used immediately in the plant’s own respiration

c.remainder is temporarily stored, eventually entering the food chain

  1. Photosynthesis and Respiration
  1. photosynthesis: the basic process whereby chlorophyll-containing plants produce stored chemical energy from water and carbon dioxide and which is activated by sunlight
  2. in the presence of sunlight a green plant takes carbon dioxide from the air and combines it with water to form carbohydrate compounds (sugars) and release molecular oxygen

1)CO2 + H2O (light) carbohydrates + O2

2)the energy of the sunlight is locked up as chemical energy in the sugars

  1. the stored chemical energy is used in two ways:

1)the chemical energy flows through the biosphere as animals eat the plants or other animals that had eaten the plants earlier

2)it is consumed by plants themselves in respiration

  1. Net Primary Productivity:
  2. net photosynthesis of a plant community over a year

(net photosynthesis is the difference between amount of carbohydrate produced in photosynthesis and that lost in plant respiration)

  1. measured in amount of fixed carbon per unit area (kg carbon/m3/year)
  2. basically a measure of the amount of chemical energy stored in a plant community
  3. biomass: total dry weight of all organic material in a plant community
  4. net primary production varies widely around the world from environment to environment (Fig 10-4)

1)highest: on land within tropics where high precipitation and insolation are available for plant growth

2)diminishes poleward, especially in extremely arid and cold environments

3)oceans: varies by nutrient content; high off west coasts of continents in midlatitudes where there’s upwelling of cold, nutrient rich water

  1. The Hydrologic Cycle
  1. water is the most abundant substance in the biosphere
  2. two ways water is found in the biosphere:
  1. in residence with its hydrogen chemically bound into plant and animal tissues
  2. in transit as part of the transpiration-respiration stream
  1. The Carbon Cycle
  1. main carbon cycle: conversion from carbon dioxide to living matter and back to carbon dioxide
  1. initiated when carbon dioxide from the atmosphere is photosynthesized into carbohydrate compounds
  2. respiration by plants, animals and soil returns carbon to the atmosphere in the form of carbon dioxide
  3. carbon moves constantly form the inorganic reservoir to the living system and back again
  1. carbon cycle operates relatively rapidly – years or centuries
  2. carbon cycle and storage
  1. <1% of total carbon on or near Earth’s surface is part of the cycle at any given moment
  2. overwhelming bulk of near-surface carbon concentrated over millions of years in geologic deposits

1)coal, petroleum, carbonate rocks

2)composed of dead organic matter accumulated mostly on sea bottoms and subsequently buried

3)carbon from this reservoir is normally incorporated in the cycle very slowly through rock weathering

4)humans’ burning of fossil fuels containing carbon has added considerable carbon to the atmosphere

  1. Renewable Energy: Biofuels
  2. alternatives to fossil fuels
  1. ethanol: alcohol fuel fermented from crops
  2. biodiesel: made by chemically processing vegetable oil or animal fat
  3. advantage: burning biofuels emits CO2 taken out of the atmosphere during current plant and animal growth while fossil fuels burn CO2 buried for millions of years
  4. disadvantage
  5. most ethanol (from corn, soy beans, switch grass, palm fruit) takes more energy to produce than it provides
  6. sugarcane ethanol:

1)provides more energy than it takes to produce

2)Brazil, the world’s largest exporter of biofuels, is major producer

3)trees storing vast quantities of carbon are lost and huge amounts of CO2 are released into the atmosphere if sugarcane replaces mature Brazilian rainforests

  1. using food crops for fuel results in higher food prices and is contributing to world hunger
  1. ethanol in the U.S.
  2. 33% of corn grown in U.S. goes into making ethanol
  3. provides equivalent of only 1.3% of total U.S. oil consumption
  4. environmental costs include impact of pesticides, herbicides, groundwater irrigation and nitrogen fertilizer (→ dead zone in Gulf of Mexico)
  5. current research involves yeast, algae and bacteria
  1. The Oxygen Cycle
  1. extremely complex cycle
  2. most of the oxygen in atmosphere is molecular oxygen (O2) largely a byproduct of plant photosynthesis
  3. some is bound up in water molecules from evaporation or plant respiration
  4. some is bound up in carbon dioxide released during animal respiration
  1. The Nitrogen Cycle
  1. 78% of air is N2 (nitrogen gas)
  2. nitrogen fixation:
  1. conversion of gaseous nitrogen into forms that can be used by plant life
  2. mostly accomplished by soil microorganisms and plant root nodules
  1. nitrogen cycle: nitrogen moves through the environment in cycle from green plans to animals to decomposition
  2. human activities (synthetic nitrogenous fertilizers and widespread introduction of nitrogen-fixing crops such as alfalfa, clover, and soybeans) excessive accumulation of nitrogen compounds in many lakes and streams→ depletes water oxygen supply
  1. Other Mineral Cycles
  1. phosphorus, sulfur, and calcium + more than a dozen other trace minerals
  2. cycled through gaseous or sedimentary pathways
  3. amounts ofbiotic nutrients available on Earth are finite – they move over and over through cycles
  1. Food Chains
  1. food chain: transfer of energy through the ecosystem by sequential predation in which organisms feed upon one another
  1. process of energy transfer is more accurately described as a web
  2. each link is an energy transformer
  1. ingests some energy of preceding link
  2. uses some of energy for own sustenance
  3. passes some of the balance of energy to next link
  1. plants are fundamental unit of food chain
  2. producers/autotrophs/self-feeders
  3. plants fix carbon and store solar energy through photosynthesis
  1. primary consumers: herbivores (plant-eating animals)
  2. secondary consumers: carnivores (meat-eating animals)
  3. there may be many levels of secondary consumers in a food chain
  1. food pyramid
  1. base (energy-trapping organisms) is much larger than apex (secondary consumers)
  2. Fig 10-10: it takes half a ton of plankton to provide a 1 pound weight gain for a human
  3. because only a portion of the stored energy is transferred from organisms of one trophic level to the next, it is much more energy efficient to eat lower on the food chain (vegetables rather than meat)
  1. Pollutants in the Food Chain
  1. biological amplification:chemical pollutants (chemical pesticides and heavy metals) can become concentrated in a food chain
  2. may result in harmful effects at higher levels of food chain
  1. Natural Distribution
  1. natural distribution of a species is determined by 4 basic conditions:
  2. evolutionary development
  3. migration and dispersal
  4. reproductive success
  5. population die-off and extinction
  6. Evolutionary Development
  1. Darwin’s theory of natural selection, simplified as “survival of the fittest” – accounts for the development of all organisms
  2. distribution of species is impacted by where they evolved
  1. Migration/Dispersal
  1. animals possess active mechanism for locomotion
  2. plants engage in passive migration, particularly dispersal of seed by
  1. wind
  2. water
  3. animals
  1. contemporary distribution pattern often result of natural migration as well as human interference
  2. examples: coconut palms and cattle egrets
  1. Reproductive Success
  1. dependent on predation, climate change, food supply, other factors
  2. changing environmental conditions can alter success of competing species
  3. reproductive success is usually limiting factor that allows one competing population to flourish while another languishes
  1. Population Die-off and Extinction
  1. Plant Succession
  1. one type of vegetation replaced naturally by another
  2. lake → marsh(reeds, sedges, mosses) → meadow (grasses and shrubs) → forest (trees)
  3. series of local animal replacements accompany plant succession because of significant habitat changes
  4. occurs gradually as well as after catastrophic natural events
  1. plant succession differs from extinction
  2. extinction: permanent elimination of a species from the entire world
  3. species succession is not permanent
  4. half a billion species have become extinct – dinosaurs, 65 million years ago, are the most dramatic example
  1. People and the Environment: Bark Beetle Killing Forests in Western North America
  2. dead and dying pine forests from infestation of the mountain pine beetle
  3. western North America from Canada to New Mexico
  4. possibly largest insect infestation in North America during historic times
  5. causes
  6. fire suppression makes a large portion of trees the same age, old enough to be susceptible to the bark beetle
  7. 10 year drought has weakened many trees
  8. climate change had resulted in less frequent severely cold winters, allowing beetle to extend its range
  9. consequences
  1. fear loss of tourism in mountain towns
  2. hot wildfires and resulting flash floods and debris flows
  3. falling dead trees
  4. environmental disaster?
  1. mountain beetle is a native species, not an exotic
  2. forests quickly regenerate after replacement events
  3. climate change is the wild card in this infestation
  1. Environmental Relationships
  2. intro
  1. both plants and animals compete with one another – for light, water, nutrients, shelter
  2. competition is
  1. intraspecific: among members of the same species
  2. interspecific: among members of different species
  1. limiting factor: the variable that is most important in determining the survival of an organism
  2. The Influence of Climate
  1. Light
  1. photosynthesis is activated by light
  2. photoperiodism: response of an organism to the length of exposure to light in a 24 hour period

1)seasonal variation in the photoperiod becomes greater with increasing latitude

2)fluctuation in the photoperiod stimulates seasonal behavior in both plants and animals

  1. Moisture
  1. the broad distribution patterns of the biota are governed more significantly by the availability of moisture than by any other single environmental factor
  1. Temperature
  1. cold-weather areas of high latitudes and high elevations have a limited number of animals and plants
  1. Wind
  1. principal negative effect: causes excessive drying by increasing evaporation from exposed surfaces
  2. in cold regions it escalates rate of animal body heat loss
  3. Edaphic Influences
  1. edaphic: having to do with soil
  2. soil characteristics have direct and immediate effect on flora, indirect effect on fauna
  3. Topographic Influences
  1. most important factor affecting global distribution patterns of plants and animals (ex: plains v. mountains)
  2. at more localized scale other factors:
  1. slope steepness
  2. slope orientation
  3. drainage
  4. Wildfire
  1. impacts composition of biota
  2. benefits of fire:
  1. help seeding or sprouting of certain plants

1)certain trees scatter seeds only after heat of fire causes cones or seedpod to open

2)California redwood, southern yellow pine

  1. maintain certain plant interactions: grasslands sustained by natural fires that inhibit encroachment of tree seedlings
  2. Environmental Correlation: Example of Selva
  1. there is an intertwining relationship between various components of the environment – one aspect of the environment affects another
  2. example: selva(tropical rainforest)
  3. vast extents in Amazon and Congo watersheds and in East Indies
  4. Climate
  1. explains the distribution pattern of selva
  2. tropical wet, Af
  3. abundant precipitation and uniformly warm temperatures
  1. Flora:
  1. unexcelled luxuriance and variety
  2. broadleaf evergreen forest dominates
  3. mostly sparse undergrowth;where light gets in jungles form
  1. Fauna
  1. abundant birds, reptiles and insects
  2. large species, especially hoofed animals, are rare
  1. Soil
  1. impacted by abundant precipitation
  2. deep but highly leached and infertile
  3. rapid weathering and decomposition
  4. reddish color indicates insoluble minerals
  1. Hydrography
  1. abundant runoff with heavy sediment load
  2. dense network of streams
  3. lakes are rare