Ecosystems and EnergyUnit 2

What is ecology?

•The study of the relationships between organisms and their environment

•Biotic factors = living factors; other organisms such as bacteria, plants, animals, fungi, etc.

•Abiotic factors = non-living factors, such as water, sunlight, rocks, air, etc.

Biological organization • Atom basic unit of

matter• Molecule• Cell basic unit of life• Tissue• Organ• Organ system• Organism• Population• Community• Ecosystem• Landscape• Biosphere

Words to know…• Population – a group of organisms of the

same species that live together in the same area at the same time

• Species – a group of similar organisms whose members freely interbreed in the wild to produce fertile offspring; members of one species do not interbreed with other species of organisms

• Community – All the populations of different species that are living together in the same area at the same time

Words to know…

•Ecosystem – a community and its physical environment; biotic and abiotic factors

•Landscape – a region that includes several ecosystems

•Biosphere – the layer of Earth containing all living organisms. As an ecological system, the biosphere interacts with the land, the water, and the atmosphere.

Earth’s Four Realms

•Hydrosphere – Earth’s supply of water (liquid and frozen, fresh and salty)

•Atmosphere – gaseous envelope surrounding the earth

•Lithosphere – soil and rock of Earth’s crust

•Biosphere – all living organisms

Life on Earth depends on 3 interconnected factors…•1. High quality energy flows in one

direction:Sun Living things (food web trophic levels) Environment Back to space (infrared energy)

•2. The cycling of matter or nutrients through different parts of the biosphere (ex. Water cycle, nitrogen cycle, etc.)

•3. Gravity, which allows the earth to hold down its atmosphere and causes the downward movement of matter in the matter cycles.

What is energy?•The capacity or ability to do work, includes the

ability to grow, move, reproduce, and maintain or repair damaged tissue

•Several different forms: ▫Chemical = stored in chemical bonds of molecules▫Radiant = transported from sun in electromagnetic

waves▫Heat = thermal energy that flows from an object with

a higher temperature to one with a lower temperature

▫Mechanical = energy in the movement of matter▫Nuclear = energy found within atomic nuclei▫Electrical = energy that flows as charged particles

How do we measure energy?

•Kilojoules – kJ, units of work•Kilocalories – kcal, units of heat energy

•1 kcal = the amount of energy required to raise the temperature of 1 kg of water by 1°C

•1 kcal = 4.184 kJ

The conversion of energy•Potential energy = stored energy•Kinetic energy = the energy of motion•Thermodynamics = the study of energy and

its transformations•System = object being studied•Surroundings = rest of universe other than

object being studied•Closed system = does not exchange energy

with its surroundings•Open system = can exchange energy with its

surroundings

Laws of thermodynamics

•1. Energy cannot be created or destroyed, but it can be transformed from one form to another.

•2. Whenever energy is converted from one form to another, some usable energy is degraded into heat, a less ordered, less usable form of energy.

•Entropy = the measure of disorder or randomness. Organized, usable energy has low entropy; disorganized energy has high entropy.

Examples• When a car is driven, only about 20% of the high-

quality energy available in its gasoline fuel is converted into mechanical energy (to propel the vehicle) and electrical energy (to run its electrical systems). The remaining 80% is degraded to low-quality heat that is released into the environment and eventually lost into space.

• When electrical energy flows through filament wires in an incandescent light bulb, it is changed into about 5% useful light and 95% low-quality heat that flows into the environment. In other words, this so called light bulb is really a heat bulb.

The Sun

•Supplies energy for photosynthesis basis of most food webs

•Powers the cycling of matter•Drives the climate and weather systems

that distribute heat and fresh water over the Earth’s surface

•Provides the natural green house effect

Photosynthesis• Biological process in which light energy from the sun

is captured and transformed into the chemical energy of carbohydrate (sugar) molecules

• Chlorophyll – photosynthetic pigment that absorbs radiant energy, gives plants and algae their green color

• 6CO2 + 6H2O light> C6H12O6 + 6O2

• Carbon dioxide + water light> glucose + oxygen

• Carbon dioxide, water, and light must be present for photosynthesis to occur

Cellular Respiration• Method used by plants, animals, or other organisms

to release the chemical energy stored in carbohydrates

• Two kinds of respiration:▫Aerobic respiration = occurs if oxygen is present▫Anaerobic respiration = occurs if oxygen is not present

• Cellular respiration:6O2 + C6H12O6 6CO2 + 6H2O + Energy (ATP)

• Recall – Photosynthesis equation: 6CO2 + 6H2O light> 6O2 + C6H12O6

Can life exist without the sun?• Yes, but there must be another source of energy• 1977 – the Alvin studied the Galapagos Rift and

found hydrothermal vents where sea water had been heated by the rocks below

• There was life, even though there was no light• The base of the food web was archaebacteria that

are capable of surviving at extreme temperatures and use chemosynthesis instead of photosynthesis

• Chemosynthesis – using inorganic compounds to obtain energy and make carbohydrate molecules, no light required

The Flow of Energy Through Ecosystems•Producers = (autotrophs) make their own

food from simple inorganic substances, form base of the food chain

•Consumers = use the bodies of other organisms as a source of food energy and bodybuilding materials (heterotrophs)▫Primary consumers = exclusively herbivores▫Secondary consumers = eat primary

consumers▫Tertiary consumers = eat secondary

consumers

The Flow of Energy Through Ecosystems• Herbivores = eat only plants• Carnivores = eat only meat• Omnivores = eat plants and meat• Detritivores = eat detritus, which is organic

matter such as carcasses, leaf litter, and feces• Saprotrophs = decomposers, microbial

heterotrophs that break down dead organic material and use the decomposition products to supply themselves with energy, releasing simple inorganic substances that can be reused by producers

The Path of Energy Flow

•Food chain = energy from food passes from one organism to the next in a sequence

•Trophic level = each level or “link” in a food chain, energy flows from level to level

•Arrows flow in direction of energy transfer

The Path of Energy Flow

•Food web = complex of interconnected food chains in an ecosystem, energy can flow along many different paths

The Path of Energy Flow

•Energy flow is linear one-way•Some energy is lost when the organism

uses it to do work•This energy is lost as heat and is

unavailable for use by any other organism in the ecosystem

•“10% rule” = only 10% of the energy is transferred to the next highest trophic level

Ecological Pyramids• Recall: What is the 2nd law of thermodynamics?• Ecological pyramids graphically represent the

relative energy values of each trophic level• Three main types:

▫Pyramid of numbers = shows number of organisms at each trophic level in a given ecosystem

▫Pyramid of biomass = shows the total biomass (quantitative estimate of total mass of living material) at each trophic level

▫Pyramid of energy = shows the energy content (usually kcal/sq. m/year) of the biomass of each trophic level

Pyramid of numbers

Pyramid of biomass

Pyramid of energy

Productivity of Producers•Gross primary productivity (GPP) = the

rate at which energy is captured during photosynthesis, the total amount of energy captured during photosynthesis in a given period of time

•Net primary productivity (NPP) = energy that remains in plant tissues after cellular respiration, the rate at which organic matter is incorporated into plant tissues for growth

•NPP = GPP – Plant respiration

Net Primary Productivities for Selected EcosystemsEcosystem Average NPP (g dry matter/sq. m/yearSwamp and Marsh 3,000

Tropical rain forest 2,200

Temperate evergreen forest 1,300

Temperate deciduous forest 1,200

Savanna 900

Boreal (northern) forest 800

Woodland and shrubland 700

Agricultural land 650

Temperate grassland 600

Lake and stream 400

Arctic and alpine tundra 140

Desert and semidesert scrub 90

Extreme desert (rock, sand, ice) 3

Human Impact on NPP

•Any NPP that is taken for human use (survival, economy, etc.) cannot be transferred to other organisms in the ecosystem

•Humans consume 32-40% of the annual NPP

What else flows through a food chain?

•Energy is not the only thing transferred from trophic level to trophic level

•Bioaccumulation = accumulation of a substance, such as a toxic chemical. In the tissues of a living organism

•Biomagnification = the increasing concentration of these toxins at successively higher trophic levels in a food chain

Where do we find these various ecosystems?•Biomes = Extensive areas of similar

climate and vegetation•Ecotones = transitional area between

two ecosystems•Ecozones (ecoregions) = smaller

regions within ecosystems that share similar physical features

Marine Ecosystems• Photic zone – relatively thin (200

meters) upper layer where light can penetrate photosynthesis can occur

• Aphotic zone – permanently dark, chemosynthetic producers only

• Marine biologists divide ocean by photic and aphotic zones as well as depth and distance from shore

• And now, to learn about some biomes…

Antarctic

•Area surrounding south pole•Rainfall: <5 cm per year•Dominant animals: penguins and marine

mammals

Benthos (Hadal)

•Bottom of oceans, too deep for sunlight no plants

•Primary source of energy = dead organic matter settling and chemosynthesis

•Creatures that live here are called benthos

Coastal Ocean

•Extends from low tide mark to outer edge of continental shelf

•Shallow enough to mostly fall in photic zone allows plankton, kelp, etc. to survive

Coral Reef• Warm, shallow water of tropical coastal oceans• Named for coral animals whose hard, calcium

carbonate skeletons make up their primary structure

• Need warm water, bright sun, and salt, grow with help of algae

• Three kinds: fringing reefs grow on continental shelves near the coastline, barrier reefs grow parallel to the shoreline but further out, and coral atolls grow in rings around the top of sunken ocean volcanoes

Desert• Between 15° and 25° north and south latitude• Rainfall: <25 cm per year• Soil: coarse texture, abundant minerals, lack organic

matter• Dominant plants: cacti and other succulents; plants with

short growth cycles• Geographic distribution: Africa, Asia, Middle East, United

States, Mexico, South America, Australia

Estuaries

•Wetlands formed where river meets sea•Brackish = fresh water + salt water•Most organic material enters as detritus •Salt marshes = temperate zone

estuaries•Mangrove swamps = tropical coastal

regions

Flowing Freshwater

•Rivers, streams, creeks, and brooks•Animals have adaptations, such as hooks,

suckers, streamlined bodies, etc.•Often come from underground water

source•Turbulent water = plenty of dissolved

oxygen

Freshwater Wetlands

•Wetland – ecosystem in which water either covers the soil or is present at or near the surface of the soil for at least part of the year

•Bogs, marshes swamps•Support very specific plants and animals•Soil is low in oxygen

Grasslands• 10-60 cm rain• Warm to hot summers; cold winters; moderate,

seasonal precipitation; fertile soils; occasional fires• Dominant plants: lush, perennial grasses and herbs;

most are resistant to drought, fire, and cold• Geographic distribution: central Asia, North America,

Australia, central Europe, and upland plateaus of South America

Hydrothermal vents

•Occur in the deep ocean where hot-water vents rich in sulfur compounds are found

•Provide energy for chemosynthetic bacteria

Intertidal zone

•Submerged in sea water once or twice a day, otherwise exposed to air and sunlight

•Zonation – prominent horizontal banding of organisms that live in a particular habitat

•Water movement brings in nutrients and removes waste

Open Ocean• Begins at edge of continental shelf and extends

outward• 90% of the surface area of the world’s ocean• Organisms are exposed to high pressure, frigid

temperatures, and total darkness• Most productivity occurs in photic zone• Low amounts of nitrogen and phosphorus not much

plant life

Savannas• Warm temperatures; seasonal rainfall; compact

soil; frequent fires set by lightning• Dominant plants: tall, perennial grasses;

sometimes drought-tolerant and fire-resistant trees or shrubs

• Geographical distribution: large parts of eastern Africa, southern Brazil, northern Australia

Standing Freshwater

•Lakes and ponds•Water flows in and out, usually circulates

helps distribute heat and oxygen•Relatively still water allows organisms

like plankton to survive

Taiga (Coniferous or Boreal forests)• 45°-60° north latitude• Long, cold winters; short, mild summers; moderate

precipitation; high humidity; acidic, nutrient-poor soils• Dominant plants: coniferous trees such as spruce and fir; some

broadleaf deciduous trees; small, berry-bearing shrubs• Soil: deep layer of litter, decomposition is slow due to cold

temperatures• Geographic distribution: North America, Asia, and northern

Europe

Temperate deciduous forests• Cold to moderate winters; warm summers; year-round

precipitation; fertile soils heavy population• Dominant plants: broadleaf deciduous trees; some

conifers; flowering shrubs; herbs; a ground layer of mosses and ferns

• Geographic distribution: eastern United States; southeastern Canada; most of Europe; and parts of Japan, China, and Australia

Temperate shrubland (chaparral)• 50-75 cm of rain, mostly in winter• Hot, dry summers; cool, moist winters; thin, nutrient-poor soils;

periodic fires• Dominant plants: woody evergreen shrubs with small, leathery

leaves; fragrant, oily herbs that grow during winter and die in summer

• Geographic distributions: western coasts of North and South America, areas around the Mediterranean Sea, South Africa, and Australia

Tropical rain forests• 200-400 cm of rain per year• Hot and wet year-round; thin, nutrient poor soils• Dominant plants: broad-leaved evergreen trees;

ferns; large woody vines and climbing plants• Geographic distribution: parts of South and

Central America, Southeast Asia, parts of Africa, southern India, and northeastern Australia

Tropical seasonal forests

•Generally warm year-round; alternating wet and dry seasons; rich soils subject to erosion

•Dominant plants: tall, deciduous trees that form a dense canopy during the wet season

•Geographic distribution: parts of Africa, South and Central America, Mexico, India, Australia, and tropical islands

Tundra• 60° north latitude and above• Strong winds; low precipitation; short and soggy

summers; long, cold, and dark winters; poorly developed soils; permafrost

• Dominant plants: ground-hugging plants such as mosses, lichens, sedges, and short grasses

• Geographic distribution: northern North America, Asia, and Europe

Ecological Succession• Succession = the process of community

development over time which involves species in one stage being replaced by different species

• Primary succession = the change in species composition over time in an environment that has not been previously inhabited by organisms▫Pioneer community = initial community that

develops during primary succession• Secondary succession = the change in species

composition over time that takes place after some disturbance destroys the existing vegetation; soil is already present

Ecological Succession• Secondary succession happens in organized, predictable

ways that vary from ecosystem to ecosystem• Usually begins with a non-diverse population of small,

short-lived, simple organisms and ends with a more diverse population of larger, long-lived, complex organisms

• Depend on 3 factors:▫ Facilitation = when one species modifies an environment

to the extent that it meets the needs of another species▫ Inhibition = when one species modifies the environment

to the extent that it is not suitable for another species▫ Tolerance = when species are not affected by the

presence of other species

Early vs. Late Secondary Succession in PlantsEarly Successional Stage Secondary Successional Stage

Limited biomass Higher biomass in tropics and wetlands, lower in deserts, tundra, etc.

Nutrients are mainly in soil and leaf litter and are quickly absorbed by simple plants

Nutrients are mainly in plants and top layers of soil, nutrient cycles slow down

Seeds have long life spans and greater tolerance for environmental change

Seeds have short life spans and less tolerance for environmental change

High NPP Low NPP

Mostly r-strategists Mostly k-strategists

Widespread seed dispersal Limited seed dispersal

Low-efficiency photosynthesis High-efficiency photosynthesis

Survival strategies

•R-strategy = mature rapidly, short life spans, high fecundity (rate of reproduction), low biodiversity, niche generalists

•K-strategy = mature slowly, longer life spans, low fecundity, high biodiversity, niche specialists

Range of tolerance

•Range of conditions in which an organism can survive; varies from organism to organism

Some more terms to know…• Ecological niche = an organisms adaptations, use

of resources, and lifestyle in its environment; how and when an organism interacts with other organisms

• Keystone species = a species that is crucial in determining the nature and structure of the entire ecosystem in which it lives; other species of a community depend on or are greatly affected by the keystone species, even though there usually aren’t many of them in the community

• Habitat = where an organism lives; physical location

Some more terms to know…

•Indicator species = used as a standard to evaluate the health of an ecosystem; more sensitive to biological changes than other species

•Indigenous species = those that originate or occur naturally in an area or environment

•Invasive species = those that are artificially introduced to an area or environment

Patterns of distribution• Clumped = some areas within the habitat are

dense with organisms, while other areas contain few members

• Random = Little interaction between members of the population, leading to random spacing patterns

• Uniform = Fairly uniform spacing between individuals

How do animals interact with one another in an ecosystem?•Symbiosis = the close, prolonged

interaction between 2 species•Amensalism = -/0, one species suffers

and the other is not affected•Commensalism = +/0, one organism

benefits and the other is not affected•Competition = +/-, can be intraspecific

(same species) or interspecific (different species), driving force of evolution, competing for limited resources

How do animals interact with one another in an ecosystem?•Mutualism = +/+, both organisms

benefit, sometimes they become dependent on one another for survival

•Parasitism = +/-, one organism benefits at the expense of another

•Predation = +/-, one organism survives by consuming the other

•Saprotrophism = +/0, one organism survives by eating an already dead organism

How do organisms deal with competition?•To survive, a species must:

▫1. Migrate to another area▫2. Shift its feeding habits or behavior

through natural selection and evolution▫3. Suffer a sharp population decline▫4. Go extinct in that area

Two main kinds of competition:•Interference competition = one species

may limit another’s access to some resource▫Response: Defend territory = release

chemicals, fight, chase away, stinging, etc.•Exploitation competition = competing

species have roughly equal access to a specific resource but differ in how fast or efficiently they exploit it▫Response: Consume faster the faster you

eat, the more you get!

Competitive Exclusion

•Two species that require the same resource cannot coexist indefinitely in an ecosystem in which there is not enough of that resource to meet the needs of both species.

How can species reduce competition?

•Resource partitioning = coexisting species’ niches differ from each other in one or more ways

Predator-Prey Relationships

•Two main methods of predation:▫Pursuit = prey is detected, chased,

caught, and killed▫Ambush = predator uses camouflage,

chemical attractants, etc. to wait for prey to approach, at which point it is killed

•Prey can use a variety of defensive mechanisms to avoid being eaten

Defensive strategies

•Protective mechanisms such as better hearing, sight, smell, etc., sitting very still, speed, etc.

•Camouflage = blending into environment•Chemical defenses = plants producing

toxins, skunk spray, etc.•Warning coloration = toxic plants or

animals have bright colors that warn predators not to eat them

Defensive strategies

•Mimicry = animals that are not toxic will use bright colors to look like those that are

•Behavioral strategies = time of day that an animal is active, frequently checking surroundings, fight-or-flight, etc.

•Living in large groups = “strength in numbers,” take turns eating, sleeping, and watching for predators

A peek at the next unit…Where did all these species come from?•Evolution = a genetic change in a

population of organisms that occurs over time

•Adaptation = evolutionary modification that improves the chances of survival and reproductive success of the population in a given environment