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Ecology

All Materials © Cmassengale

Ecology is the study of interactions between organisms (biotic part) and their nonliving environment (abiotic factors)

Biotic factors includes plants, animals, fungi, & microorganisms. They may be producers, consumers, or decomposers.

Abiotic factors include climate, soil, temperature, water, air, sunlight, humidity, pH, and atmospheric gases.

Habitat is the place a plant or animal lives, while its niche is its total way of life.

Life is organized into levels:

Organism (any single living thing)

Population (members of the same species living in one place)

Community (all the populations living in a defined area)

Ecosystem the Community living in a similar habitat, ecosystems consist of both

biotic and abiotic components

iomes Ecosystems covering a wide area with similar climates and organisms

iosphere all the living and nonliving things on Earth

Producers:

Make their own food through photosynthesis or chemosynthesis. Autotrophic

Includes: plants, algal, protists, and some bacteria

Consumers

Can not and do not make their own food. Need to eat something that is an autotrophe or eat something that ate an autotrophe.

May be herbivoures, feed only on plants, carnivores feed only on meat or omnivores feed on plants and animals.

Decomposers:

Break down dead plants and animals into their inorganic component part to be

Recycled (nutrients) in the soil for producers to use. Called detritivores and include bacteria, fungus and mold.

Sunlight is the ultimate energy for all life on the surface of the planet and the upper regions of the oceans. But only producers can get their energy from sunlight and convert it into a biological storage form of glucose.

a food pyramid is divided into tropic levels- these are feeding levels of producers and consumers in an ecosystem. Each tropic level is all the biomass that supports the levels above it.

1st tropic level are the producers that use sunlight directly or in deep marine environments the chemotrophes bacteria that feed on methane or sulfur compounds.

2nd tropic leve includes herbivores that feed on the plants directly or the organisms in the deep chemotrophe sink areas feed on the bacteria.

The higher tropic levels 3rd and 4th in some cases are the carnivores that feed on level 2, 3 and sometimes 4.

Food Chains and Food Webs:

Chains show who eats whom in an ecosystem in a single organism to single organism passage of energy

Webs are made up of several food chains and the interconnections, showing that organisms have more than one food source in the ecosystem.

Always begin with the producers, and their initial energy source.

Producers store energy in the chemical bonds of the food, glucose, they make

Stored energy is passed to consumers when they eat the producers or other consumers

Someenergy is lost at each tropic level as heat when chemical bonds are broken or lost if the consumer can not digest the stored form.

Both energy and nutrients must move through the ecosystem.

Populations

Populations (included in Biome Project) • A population is a group of individuals of a species that live together and influence each

other’s survival

• Populations have several properties that can describe them population range is the area throughout which a population occurs population distribution is the pattern of spacing of individuals within that range population size is the number of individuals in the population population density is the population size that occurs in a given area population growth describes whether a population is growing or shrinking, and

at what rate No population occurs in all habitats worldwide

Most species have relatively limited geographic ranges Each population has its own requirements that determine where it can live and

reproduce temperature, humidity, food Ranges may expand or contract in response to environmental change

Altitudinal shifts in population ranges in the mountains of southwestern North America

Population Distribution • Populations may be distributed randomly, uniformly, or clumped • Random spacing occurs when individuals do not interact strongly with one another or

with nonuniform aspects of their environment not common in nature

• Uniform spacing often results from competition for resources territories provide exclusive access to resources such as food, water, refuges, and

mates • Clumped spacing occurs in response to uneven distribution of resources in their

immediate environments social interactions also can lead to clumped distributions common in nature

• Dispersal mechanisms to colonize new areas may occur through water wind transfer from an animal traveling between locations

• Humans have altered population ranges of organisms by altering the environment • Humans have served as an agent of dispersal for many species

Population Growth • Critical properties of any population include

population size - the number of individuals in the population population density - the number of individuals that occur in a unit area population growth - capacity to grow

• A population’s growth rate is the difference between the birth and death rates, corrected for movement of individuals into (immigration) or out of (emigration) the population

when a population’s growth rate remains constant, the population experiences rapid growth called exponential growth

in natural populations, exponential growth only prevails for short periods, such as when an organism reaches a new habitat

Exponential growth in a tree population

• A population ultimately stabilizes at a certain size, called the carrying capacity the carrying capacity is defined as the maximum number of individuals that an

area can support

• No matter how rapidly populations grow, they eventually reach a limit imposed by shortages of important environmental factors at this point, the population begins to experience logistic growth

Most natural populations exhibit logistic growth

• Logistic growth can best be represented by a sigmoid growth curve or S curve growth is rapid at first when the population is small, then tapers off at an

increasing rate as population size approaches carrying capacity

• Logistic growth is characteristic of most biological populations Compare the two growth curve types

The Influence of Population Density

• Many factors act to regulate the growth of populations in nature

density-independent effects • these effects regulate population growth regardless of population size • for example, weather effects or geological events (i.e., volcanoes)

density-dependent effects • the effect that these factors have on population growth depends on

population size • these effects grow stronger as the population size increases

• In natural systems that are exploited by humans, the aim is to maximize productivity by exploiting the population early in the rising portion of its sigmoid growth curve commercial fisheries, for example, attempt to operate so that they harvest a

population near its point of maximal sustainable yield

i. ii.

iii. Introduction—hierarchy activity iv. Richness/evenness-- Bird Island activity v. Density dependent/independent factors – Dominos Demo

vi. Population growth curves vii. carrying capacity

Communities (included in Biome Project) viii. Interactions (symbiosis, predator/prey, competition, keystone species,

etc.)—Soaring Eagle lab ix. Succession

• Community refers to the species that occur at any given locality communities can be characterized by either their constituent species (a

list of all species present in the community) or by their properties, such as primary productivity

interactions among community members govern many ecological and evolutionary processes

• for example, predation, competition, and mutualism affect the population biology of a particular species, as well as the way in which energy and nutrients cycle through the ecosystem

• Coevolution is the adaptation of a species to the other organisms in its community examples of coevolution include

• plants and animal pollinators • predator-prey interactions • symbiotic relationships

Pollination by bat

Coevolution and Symbiosis

Symbiosis means “living together”. – Describes situation in which members of two species live in close

physical relationship – Not always positive for both species

• In a symbiosis, two or more kinds of organisms live together in often elaborate and more or less permanent relationships there are three major kinds of symbiotic relationships

• mutualism • commensalism

• parasitism

• Mutualism is a symbiotic relationship in which both species benefit

The pistol shrimp defends the coral, which he calls home—an example of mutualism

– Commensalism is a symbiotic relationship that benefits one species but neither hurts nor helps the other. Example Sharks and remora

– Trees and epiphytic plants.Oxpeckers eat insects off an impala—an example of commensalism

Parasitism is a symbiotic relationship in which one species benefits while the other is harmed

Involves one organism living in or on another living organism in order to obtain nutrients

– The parasite benefits and the host is harmed. – Parasites usually do not kill their host immediately because they need

nutrients from it. However, as the parasite drains nutrients from the host, the host is

weakened and may die. – Bacteria, viruses, protists, plants, fish, insects, worms, mites, and ticks

all have species that are parasites. – There are more parasitic species than nonparasitic species in the world.

Internal parasites – Live inside their hosts – Tapeworms, bacteria, protozoa

External parasites – Live on the exterior of their hosts – Fleas, ticks

There are even parasitic plants – Indian pipe

Examples

Mosquito: Females ingest blood for the protein. Male mosquitos ingest plant juices.

Dirofilaria immitis: Heartworm of dogs, whose adults reside in the right side of the heart.

• Predation is the consuming of one organism by another in nature, predators often have large effects on prey populations

• population cycles may be, in some situations, stimulated by predators

• a classic example is the “10-year cycle” of the snowshoe hare, Lepus americanus, that appears to be under the influence of food plants and predators

under laboratory conditions, predators may exhaust their prey species and then starve

prey predator cycles

Predation occurs when one organism is captured, killed, and eaten by another. – The predator is the killer and the prey is killed.

– Predators have evolved specific methods for capturing prey. Chase and kill (leopards, lions, etc.) Camouflage, wait and strike (frogs, lizards, etc.) Use tools to capture and kill (spiders and webs)

Affects on Prey

Prey populations are controlled by predators. Predators act as selecting agents on prey populations by eliminating less well-

adapted prey individuals. Predators remove sick and injured prey, which can control the spread of disease

in the prey population.

• Predator-prey interactions are an essential factor in the maintenance of communities that are rich and diverse in species predators prevent or greatly reduce competitive exclusion by reducing

the number of individuals of competing species • Plants have evolved many mechanisms to defend themselves against predators

Physical defenses: spines, thorns, prickles Chemical defenses: chemicals that make the plants toxic to herbivores

• some herbivores have, as a result, evolved a tolerance to these chemicals and may use them for their own defense

many animals have defensive coloration • aposematic coloration is a warning coloration that is

characteristic of animals that use poisons • cryptic coloration is color that blends in with surroundings

Ecological Succession

A climax community is a stable, long-lasting community. When communities change from one type to another, succession occurs.

– Successional stages lead to a climax community. Primary succession occurs when a community develops where non-previously

existed. Secondary succession occurs when a community is disturbed and regenerates.

• Succession is the orderly replacement of one community with another primary succession

• occurs on bare, lifeless substrates, such as those left behind when a glacier retreats or when a volcanic island emerges

• pioneering community is the first to become established • Pioneer organisms grow first and establish

a pioneer community. Bacteria, algae, fungi, and lichens Lichens are particularly important.

• Combination of algae and fungi • Able to grow on bare rock • Capable of photosynthesis and can form new organic matter • Small consumers can eat lichen. • Breaks down rock and liberates minerals • Soil begins to form.

• As soil forms, small plants become established. This adds more soil.

• As larger plants are established smaller plants die out. Shade from tall plants makes it difficult for shorter plants to survive.

• Succession from this point depends on the climate. • Each stage in plant succession is accompanied by specific kinds of animals

secondary succession • occurs after an already established community has been disturbed

• Occurs after a community is altered by a natural or human-induced disaster Hurricane, fire, abandoned agricultural land

• Soil is already present. • A reservoir of seeds from plants still exists from the original community. • A pioneer community of weeds appears first.

Then grasses emerge Grasses can support insects, small mammals, and birds.

• If rainfall is adequate Shrubs and small trees will begin to grow. Larger trees will follow and grasses will die out.

Three main elements that must move through an ecosystem:

Water

Carbon and

Nitrogen

The follow up 4th is phosphorous

Water or Hydrologic Cycle:

Cells are 70-90$ water, water is needed for metabolic processes serving as a solvent in biological organisms as we understand them, water is the most important element for terrestrial organisms because they loose water to the surrounding environment- desiccation or drying out.

Steps in the water Cycle:

Evaporation Transpiration (water loss from lakes, rivers, oceans...) (water loss from plant leaves)

Condensation water vapor forms clouds or fog

Precipitation

Water returns to the surface of the Earth in the form or rain, sleet, snow…

Surface Runoff returns water to the surface or to ground water.

USGS water cycle http://water.usgs.gov/edu/watercycle.html

Carbon Cycle:

Consists of photosynthesis, cellular respiration and decomposition

Begins with producers taking carbon dioxide from the air to use during photosynthesis to make glucose.

The carbon dioxide in the glucose is used during cellular respiration to make ATP the energy of biological work and CO2 is made as a waste product.

Decomposing plants and animals return carbon to the soil and air.

Carbon Cycle Steps:

Plant leaves take carbon dioxide from air

plants convert carbon dioxide into carbohydrates – glucose and store it as starch or use to make

their structures- grow- as cellulose.

plants and animals release carbon dioxide back into the air during cellular respiration

Decomposers return carbon products to the soil and water to be reused by producers.

Nitrogen:

Needed by all organisms

Used to make proteins & nucleic acids (DNA & RNA) Air made up of 80% nitrogen

Only Cyanobacteria & Rhizobium bacteria can use nitrogen directly from the air (nitrogen fixation) Bacteria found in the soil & on the roots of legumes (beans, peas ...)

Steps in the Nitrogen Cycle:

Cyanobacteria & Rhizobium take nitrogen from air (nitrogen fixation)

Convert Nitrogen gas into ammonia

nitrifying bacteria in the soil convert ammonia into nitrates

plants can use the nitrates to make proteins

Consumers eat the plants an get the proteins containing nitrogen

Decomposers break down dead organisms and return the nitrogen to the air and soil called ammonification

anaerobic bacteria (work without oxygen present) in the soil release nitrogen from the nitrates into the air, called denitrification.

The world can be subdivided into different types of communities called biomes.

Biomes are particular communities or organisms that are adapted to a particular set of climate conditions.

– These conditions include Precipitation types and amounts Temperature ranges

The Influence of Precipitation and Temperature on Vegetation

Three main types of ecosystems:

Terrestrial (land) Freshwater (rivers, ponds, lakes ...) Marine (oceans & seas)

Terrestrial ecosystems are divided into 7 biomes with similar climates & organisms

Seven Terrestrial Biomes:

Tropical Rain Forest (jungle) Savanna (tropical grasslands) Deserts

Grasslands

Deciduous Forest Taiga (coniferous forest) Tundra

Tundra:

Cold & dark most of the year

Includes the arctic

Permafrost is the top layer of soil that thaws & in which plants grow

No trees, but sedges & grass, mosses, & lichens

Many migratory animals

Lemmings & ptarmigans are year round residents

Approximately 20 cm annual rainfall

Taiga:

Coniferous forest Extends across northern Eurasia & North America Contains conifers or evergreens (spruce, cedar, fir, pine ...) Needle like leaves withstand weight of snow Bear, deer, moose, wolves, mountain lions ... Sequoia or redwood (largest conifer) grows here Bristle cone pine oldest living conifer found here

Temperate Deciduous Forest:

South of taiga in North America, eastern Asia, & Europe High annual rainfall (75-150 cm) Moderate temperatures Well-defined seasons of about equal length Trees loose leaves in winter (deciduous) Show stratification (plant layers):

1. Canopy - broad leaf deciduous trees forming uppermost layer 2. Under story - shrubs 3. Forest Floor - herbaceous plants

Songbirds, deer, rabbits, foxes, squirrels, frogs 7 toads, lizards ...

Tropical Rain forest:

Near equator

Warm climate (20 -25 degrees C) Plentiful rainfall (190 cm/year) Contains the greatest diversity of plants & animals Insects, monkeys & apes, snakes, tropical birds, leopards... Animals & plants brightly colored Poor soil for agriculture

Grasslands:

Mostly grasses with a few trees due to less rainfall Moderate climates Good for agricultural crops Grazing & burrowing animals dominate Also called prairies

Savanna:

Tropical grasslands Warm climate & rainy season Antelope, zebra, lions, wildebeests, hyenas, elephants... Suffer from floods & drought

Deserts:

Low annual rainfall Subject to strong winds Days usually hot & nights cold Sahara desert is without vegetation Succulents such as cacti & other water storing plants Most animals nocturnal Lizards, snakes, roadrunners, insects, tarantula, hawks, rodents, coyotes...

Aquatic Biomes:

May be freshwater or saltwater Wetlands near oceans have brackish water (mixture of fresh & salt waters) Part of the part water or hydrologic cycle Often polluted by man's activities

Lakes & Rivers:

Freshwater Oligotrophic lakes are nutrient poor (catfish, carp...) Eutrophic lake are nutrient rich (trout, bass...) Deep lakes have layers or strata where different plants & animals live Phototropic organisms in upper layers for light Estuary at mouth of river contains brackish water

Ocean Zones:

Major Marine Ecosystems

Pelagic—consists of organisms that float or actively swim in the ocean Benthic—consists of organisms that live on the ocean floor Estuaries—shallow, partially enclosed areas where freshwater enters the ocean

– Brackish

Pelagic Marine Ecosystem

Plankton are so small and weakly swimming that they are carried by the ocean currents. Phytoplankton carry out photosynthesis.

– Majority are bacteria or algae – Commonly found in the upper layer of the ocean, known as the euphotic zone – Dependent on material dissolved in the water

Zooplankton are weakly swimming animals that feed on phytoplankton. Larger animals (fish, shrimp, etc.) feed on zooplankton.

Benthic Marine Ecosystems

Consists of organisms that live on ocean floor (whether attached or not) Photosynthesis by seaweed can occur in shallow regions. Food sinks to bottom from upper water layers Material that makes up the ocean bottom is important in determining the type of

community. – Sand makes it difficult for plants to attach, but is good for crustaceans. – Mud provides suitable habitat for rooted vegetation, and burrowing organisms

that filter feed in the water above the mud. – Rocky surfaces provide a good substrate for large algae and a variety of animals.

Temperature also affects the type of benthic community that is present.

Two Types of Benthic Marine Ecosystems

Coral reef ecosystem – Dependent upon photosynthesis, so found at shallow depths

Abyssal ecosystem – Found on the bottom at depths below the euphotic zone – No photosynthesis

Estuary

Shallow, partially enclosed areas where freshwater meets the ocean Sediments from rivers accumulate in estuaries. Saltiness changes with the ocean tides and the flow of the rivers. Organisms are specially adapted to these conditions. Phytoplankton and algae provide photosynthetic activity which supports the ecosystem. Important as nursery sites for fish and crustaceans

Intertidal zone 1. Along shoreline 2. Wave action 3. Lots of light so many producers 4. Starfish, sand dollars...

Neritic Zone 1. Ocean water above continental shelf 2. Coral reef found here 3. Surrounds continents & receives light in upper layers

Oceanic Zone 1. Beyond continental shelf 2. Deepest area (up to 7 miles) 3. Bottom doesn't receive light so animals adapted to darkness (many produce their own light, feed on other animals...) 4. Deepest area called abyss 5. Upper area gets light & called the photic zone (lots of seaweed here) 6. Floaters called plankton (microscopic organisms) 7. Swimmers such as fish called nekton 8. Bottom dwellers called benthos