Bio Chapter 1 Science 20

Biosphere

The narrow zone around the earth where life exists

Components of Biosphere

Lithosphere (solid earth), Hydrosphere (water), and Atmosphere (air)

Biotic factors

Living organisms and life forms

Abiotic factors

Nonliving components including geological and physical factors

Ecological studies examine four levels

organism → population → community → ecosystem

Habitat

The abiotic and biotic factors that encourage an organism's survival

What is the most important abiotic factor in any ecosystem

Water

• Habitat determines

available water, sunlight, and temperature for growth and survival

• Nutrients

Needed compounds/elements used by organisms to grow and reproduce

• Fertilizers

Chemicals containing nitrogen and phosphorus applied to increase crop yield

• Natural fertilizers

Manure contains nitrogen which is ammonified in soil, then nitrified to produce usable nitrates

• Commercial fertilizer labeling

Three numbers indicate percentage composition by weight : First number, Nitrogen (%) Second number, Phosphorus (%) Third number,Potassium (%)

• Eutrophication

A process in which nutrient runoff causes photosynthetic organisms in water bodies to multiply rapidly

• Unnatural eutrophication

Caused by agricultural runoff and livestock operations with excess nutrients

• Algal blooms

Harmful rapid growth of algae causing eutrophication

• Process

High P and N compounds → algal bloom → algae die and decompose → decomposers multiply and consume oxygen → low oxygen conditions → other organisms die out

• Eutrophic water

Water with oxygen levels too low to support animal life

• Oligotrophic lake

Nutrient-poor, photosynthesis-limited, clear water, oxygen-rich

• Eutrophic lake

Nutrient-rich, high photosynthesis, murky water, oxygen-poor

• Water plays critical roles

Maintains global heat balance, Acts as a solvent in chemical reactions, Continuously cycles between atmosphere and earth, Volume of water remains constant; specific amounts vary in different phases (liquid, gas, solid)

• Ecology

Study of interactions of living organisms with their environment and each other

• Biomass

Dry mass of all organisms in an environment

• Symbiosis

"Living together"—a long-lasting relationship benefiting at least one organism of two different species

• Mutualism

Both species benefit (e.g., butterfly-milkweed, ant-acacia mutualism, flower pollination)

• Commensalism

One organism benefits, the other is unaffected/unharmed

• Parasitism

One organism (parasite) benefits by harming the other (host)

• Predation

One organism (predator) kills the other (prey)

• Competition

occurs when two or more organisms compete for the same resource

• Matter

Everything that takes up space and has mass

• Energy

The capacity to do work

• Biosphere is composed of various ecosystems with structure based on

Energy flows, and Matter cycles

• Primary consumers

Herbivores (eat only plants)

• Secondary and tertiary consumers

Carnivores (eat other animals) and omnivores (eat both producers and consumers)

• Scavengers

Eat tissues from dead organisms

• Decomposers

Break down complex molecules into simple sugars

Trophic level

Category of organisms defined by how they obtain energy

• Food chain

Simple, linear feeding sequence showing who eats whom; not representative of complex ecological relationships

• Food web

Interconnected food chains within an ecosystem highlighting complex, real-world interactions

Food webs

show connections from primary producers through consumers and back to decomposers

• Energy loss at each step in food chain/web

approximately 90% lost

• 10% rule

Only about 10% of energy consumed at one level passes to the next trophic level

Consequences of energy loss

1. Lower productivity at higher trophic levels results in less biomass. 2. Lower biomass at higher levels combined with large body sizes results in lower population densities

1. Pyramid of Numbers

Shows number of organisms at each trophic level- Each bar represents relative numbers-Based on data from specific area (e.g., 1 km²)

2. Pyramid of Energy

Shows energy stored by each trophic level-Measured in calories or Joules-Units: Kcal/m²/yr

3. Pyramid of Biomass

Shows stored energy represented by dry weight-Units: g/m²/yr-Ecosystem Stability-Most stable ecosystems have complex, well-developed foodwebs- Removal of one organism may have little effect on complex systems

Laws of Thermodynamics

"Energy cannot be created or destroyed, only changed from one form to another" /First Law- Energy conservation—transformation between forms Second Law- With each successive energy transfer, less energy is available to do work. In biological systems, this "waste" energy is often heat.

Application

Energy flows through ecosystems; it does not cycle like matter

• Matter is

recycled; energy is not

• Biogeochemical cycles

Movement of elements/compounds between abiotic and biotic parts of the environment

• Carbon

is a component of all living and dead organisms (organic matter)

• Photosynthesis

Plants convert carbon dioxide to glucose

• Cellular respiration

Animals and plants convert glucose with oxygen to produce carbon dioxide and energy

• Decomposition

Soil organisms (bacteria) decompose dead organisms and return carbon

• Carbon sinks

Reservoirs of carbon

• Dead organisms

compressed into fossil fuels, Burning releases carbon into atmosphere, Added carbon disrupts natural cycling and leads to climate change

Greenhouse Effect

Carbon dioxide traps energy in the atmosphere, Increases temperature of the earth, Results in global warming

Nitrogen is

essential component of all proteins and nucleic acids

Four Processes

1. Nitrogen fixation: Bacteria (90%) and lightning (10%) convert atmospheric nitrogen into forms usable by plant roots (legumes); fertilizers increase this amount 2.Ammonification: Decomposers convert nitrogen products from tissues into ammonia (NH₃) 3. Nitrification: Nitrifying bacteria change ammonium ions into nitrates (NO₃⁻); plants absorb nitrates and use them to make amino acids; consumers obtain these when eating plants 4. Denitrification: Bacteria convert ammonia back to nitrogen gas, which returns to atmosphere

Limitation

Most organisms cannot use atmospheric nitrogen directly; it must be made available through these processes

Pesticides

Benefits to society- Reduce number of pests (weeds, molds, insects, birds) to increase crop production- Reduce spread of disease (malaria, West Nile) Negative impacts on ecosystems: Elimination of insect species can trigger cascading food web collapse (example: DDT on island—insects disappeared → lizards disappeared → cats disappeared → rat population increased → disease outbreak)

• Biological amplification/magnification

Buildup of toxins as you move up a food chain

• Higher trophic levels have

greater concentration of toxins