ECOLOGYEnergy in an Ecosystem

Species Interactions

Population DynamicsFrom: Kristal Schneider - Germany

ENERGY AND THE ECOSYSTEM

Food Chains and Food Webs

Energy in the Ecosystem is transferred through the different trophic (feeding) levels. Food Chain – a sequence of organisms, each of

which serves as a source of food or energy for the next.

Food Webs – a series of interconnected Food chains.

Chemical energy and nutrients travel through trophic levels primarily through photosynthesis, feeding, and decomposition.

Food Chains and Food Webs Each trophic level contains a certain

amount of biomass where chemical energy is stored Biomass is the dry weight of all organic matter

in organisms As chemical energy travels through trophic

levels: Decrease in amount of high-quality energy

available at each succeeding energy level (10%)

Some useful chemical energy is lost to the environment as low-quality heat (90%).

Producers and Consumers

Producers Land – Plants Water – Phytoplankton, aquatic plants, algae

Consumers Herbivores

Eats plants Zooplankton, grazing animals such as cows, goats,

and sheep Carnivores

Consume other animals such as herbivores Sharks, Lions, Tigers, Crocodiles

Omnivores Eat both plants and animals Turtles, Bears, Skunks, some lizards

Food Web

Food Chain

Energy Efficiency Question

Assuming 10% ecological efficiency, if green plants capture 10,000 units of energy, how much chemical energy will be available to support herbivores and carnivores?

Energy Efficiency

The Importance of Producers

The amount of living organic material that a particular ecosystem can support is determined by how much solar energy its producers can capture and store as chemical energy.

Global oceanic and terrestrial photoautotroph abundance, from September 1997 to August 2000. As an estimate of autotroph biomass, it is only a rough indicator of primary production potential, and not an actual estimate of it. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center and ORBIMAGE.

The Importance of Producers

Different areas in the planet, both terrestrial and aquatic, have variable primary productivity due to the amount of sun and nutrients available.

http://marine.rutgers.edu/opp/Production/html_files/Annu_Glb_T_noCld_Inh1.html

SPECIES INTERACTION

Species Interact in Three Ways There are three basic types of species

interactions: Competition Predation Symbiosis

These interactions help influence survival techniques which make them agents of Natural Selection.

Competition• The most common interaction between

species is competition. One species will eventually become more

efficient in acquiring resources and food.

2 types of competition Interspecific competition

Occurs between 2 or more individuals from two different species

Intraspecific competition Occurs between 2 or more individuals of the

same species

Competition - Niches

Niche – a species’ way of life or role in the community Includes everything that affects its

survival and reproduction

When two species compete for food in the same niche, their niches overlap Remember only one species can

occupy a niche at a time.Competitive exclusion principle.

Predation

All organisms need food to survive Plants make their own All others must eat

Predation is the interaction between a feeder (predator) and what it eats (prey).

Herbivores, Carnivores and Omnivores are all predators.

Prey

To evade predators, many prey species have developed ways to defend themselves. Physical barriers and strengths

Spines, shells, thick bark Faster escape and strong senses

CamouflageCuttlefish

Chemical Warfare Poisonous to eat or create poison that they

excrete when aggravated. Taste Bad

Benefit of Predator-Prey Relationships Predation plays a major role in

Natural Selection Predators weed out the weak, sick, and

dying species. Increases biodiversity

Help keep grazing animals down and preserve the balance of an ecosystem.

Symbiosis

Symbiosis is when two species live together in some form.

Three Types of Symbiosis: Parasitism Commensalism Mutualism

Parasitism

Parasitism occurs when one species (the parasite) feeds on the body of, or the energy used by, another organism (the host), usually by living on or in the host.

Common Characteristics of Parasites: Smaller than the host Rarely Kill the Host Live directly on or in the Host

Parasitism: Tree with Parasitic Mistletoe, Trout with Blood-Sucking Sea Lampreys

Commensalism

Two species interact so that one species benefits and the other is not harmed or benefits lightly.

Commensalism: Barnacles live on whales and filter food as the whale swims. Doesn’t harm or benefit whale

Mutualism

An Interaction where both species benefit from living together. Nutrition Protection Hygiene Health

Mutualism: Oxpeckers Clean Rhinoceros;

Anemones Protect and Feed Clownfish

Checkpoint #1

A tapeworm, which may reach a length of 20 feet, inhabits the intestines of a human. The worm absorbs the nutrients digested by the human.

 What type of relationship does this illustrate?  How is each organism affected by this

relationship?

Checkpoint #2

In Texas, cattle egrets (large white birds) are often found near cattle. Sometimes they are seen riding on the backs of these cattle where they are believed to feed on insects within the cattle’s fur. They can also be seen feeding on insects that the cattle stir up in the grass as they walk.

 

What kind of relationship is this?

 

How is each animal affected by this relationship?

Food Web 1.How much of the Earth’s surface is covered by oceans?

2.Consider the food web here. What would happen if we removed the krill?

3.Is the squid a primary or secondary consumer?

4.Which of the following is an example of an autotroph?1.Whale2.Squid3.Phytoplankton

Native vs. Non-native

Niches can be divided into the roles species play in their community: Native Non-native Indicator Keystone Foundation

Native vs. Non-native

Native species are those individuals that normally live and thrive in a particular ecosystem.

Non-native species are those individuals that migrate or are accidentally or deliberately introduced to a particular ecosystem. Invasive, alien, or exotic

Native vs. Non-native

Non-native species can be good or bad. Good NN

Cows, chickens, and other domesticated animals

Bad NN Kudzu Vine, Water Hyacinth, Hydrilla, and Killer

Bees

Indicator Species

When an ecosystem or community starts to collapse, ecologist look at indicator species for the first warning signs.

Indicator species are, generally, specialist species that are affected by a change in one or more key abiotic factors in the environment.

Indicator Species

Examples of Indicator Species: Trout for water quality Walleye spawning for climate

change Frogs a general measure of

productivity in a region.Tropical Regions

Keystone Species

Keystone species have a large effect on the types and abundances of other species in an ecosystem. Ex: Mangrove Crab and Sea Otters

Two major roles of Keystone Species Pollinator/Life support Top Predator

Loss of Keystone Species usually lead to a population crash and other extinctions

Keystone and Foundation Species Foundation species play a major role in

shaping communities by creating and enhancing their habitats in ways that benefit other species. Elephants push over trees and uproot

plants to help new plants take root. Beavers create dams and cut down trees.

HUMAN IMPACTSInvasive Species:

Species introduced by man, deliberately or accidentally, into a local ecosystem where the new species have caused a dramatic change in the roles of other species within the original ecosystem. Biggest cause of animal and plant extinctions About 50,000 nonnative species now live in the US and about 1 and 7 of them are harmful

INVASIVE SPECIES

Silver Carp (Asian Carp)

Asian carp were introduced to the United States in the early '70s to control algae in catfish farms in the South. Floods washed them into the Mississippi River in the 1980s. They've worked their way upriver ever since.

INVASIVE SPECIES

Many invasive species have been introduced intentionally.

Figure 11-Figure 11-1111

Fig. 11-11b, p. 234

Gypsy moth larvae

Accidentally Introduced Species

Sea lamprey(attached to lake trout)

Argentina fire ant

Brown tree snake

Eurasian ruffe Common pigeon(Rock dove)

Formosan termiteZebra mussel Asian long-horned beetle

Asian tiger mosquito

Fig. 11-13, p. 236

• Climate similar to habitat of invader

• Absence of predators on invading species

• Early successional

systems

• Low diversity of native species

• Absence of fire

• Disturbed by human activities

Characteristics ofSuccessful

Invader Species

• High reproductive rate, short generation time (r-selected species)

• Pioneer species

• Long lived

• High dispersal rate

• Release growth-inhibiting chemicals into soil

• Generalists

• High genetic variability

Characteristics ofEcosystems Vulnerable

to Invader Species

INVASIVE SPECIES

Prevention is the best way to reduce threats from invasive species, because once they arrive it is almost impossible to slow their spread.

Figure 11-Figure 11-1313

Biomagnification in Populations

A chemical increases in concentration as it moves up the food web

Each year pesticides: Kill 6 -14 million fish. Threaten 1/5th of the

U.S.’s endangered and threatened species.

Example of biomagnification of Example of biomagnification of DDT in an aquatic food chain.DDT in an aquatic food chain.

Figure 11-Figure 11-1515

Eutrophication

Caused by runoff of nutrients or fertilizers that speed the growth of marine autotrophs

Causes red tides, yellow foams, and thick green slimes of plankton blooms.

Toxic substances released from the algae can sicken or kill other species

Case Study: The U.S. Endangered Species Act

Endangered species: so few individual survivors that it could soon become extinct.

Threatened species: still abundant in its natural range but is likely to become endangered in the near future.

One of the world’s most far-reaching and controversial environmental laws is the 1973 U.S. Endangered Species Act (ESA). ESA forbids federal agencies (besides defense

department) to carry out / fund projects that would jeopardize an endangered species.

ESA makes it illegal for Americans to engage in commerce associated with or hunt / kill / collect endangered or threatened species.

Endangered Aquatic Species

Mottled Eagle Ray Michoacan Stream

Salamander Tasmanian Giant

Freshwater Lobster Blue Whale South Asian River

Dolphin

POPULATION DYNAMICS

Exponential Vs. Logistic Growth

Biotic Potential is the capacity for population growth under IDEAL conditions.

Intrinsic Rate of Increase (r) is the rate at which the population of a species would grow if it had unlimited resources. Individuals that have a high intrinsic rate:

Reproduce early Short Generation Time (time between successive

generations) Reproduce Many Times Many offspring in each generation

Reproductive Patterns

Species have different Reproductive Patterns that can help enhance their chance for survival: r-selected species *note that the r is not capitalized

K-selected species

r-selected species

These species are those that have a high intrinsic rate of increase. What are the common traits had by those that

have a high intrinsic rate of increase? Many offspring Usually small offspring Little or no parental care

Examples of r-selected species: Algae, bacteria, rodents, frogs, turtles, annual plants,

and most insects r-selected species are opportunists

When conditions are right they have a boom in reproduction.

K-selected species K-selected species are also called

competitor species. Reproduce later in life with small number of

offspring Develop inside their mother and are rather

large at birth and mature slowly. They are cared for by the parent species. Called K-selected because they live well when

the population is near the Carrying Capacity. Examples of K-selected species:

Large Mammals, birds of prey, large-long lived plants.

Exponential vs. Logistic Growth No population can grow indefinitely

Limiting factors Environmental Resistance is the

combination of all factors that act to limit the growth of a population.

Biotic Potential + Environment Resistance = CARRYING CAPACITY

Exponential vs. Logistic Growth

Carrying Capacity (K) is the maximum population of a given species that a particular habitat can sustain indefinitely without being degraded.

A population with few limitations can grow exponentially Exponential growth starts slowly

but then accelerates as the population increases. J-Shaped Curve

Exponential Vs. Logistic Growth

Logistic Growth involves rapid exponential growth followed by a steady decrease in population growth until the population size levels off. Yields an S shaped or sigmoid curve

Logistic Growth occurs because of environmental resistance. What happens if that resistance

disappears?

Population Changes

The are four general patterns of variation in population size: Stable Irruptive Cyclic Irregular

Population Changes

Stable Very little fluctuation around the carrying

capacity of the area Species found in the tropical rainforest exhibit

stable population changes because the weather and climate changes very little from year to year

Irrupt When population growth occasionally

explodes to a high peak then crash to a more stable lower level. Algae and insects

Population Changes

Cyclic Fluctuations Similar to irruptive but the cycle is drawn out

much longer. Lemmings populations rise and fall every 3-4 years Lynx and hare populations rise and fall on a ten

year cycle. Predator-prey relationships have cyclic fluctuations

Irregular Patterns No discernable pattern in population change