Fall 2019 APES chapter 4

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Lecture Outlines

Chapter 4

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This lecture will help you understand:

 Species interactions

 Feeding relationships, energy flow, trophic levels, and food webs

 Keystone species

 The process of succession

 Potential impacts of invasive species

 Restoration ecology

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Central Case Study: Black and White and Spread All Over: Zebra Mussels Invade the Great Lakes

 In 1988, zebra mussels were accidentally introduced to Lake St. Clair in discharged ballast water

 By 2010, they had invaded 30 states

 No natural predators, competitors, or parasites

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Species Interactions

 Species interactions shape and define communities

 Natural species interactions:

 Competition  relationship in which both species are harmed

 Exploitative  one species benefits and the other is harmed

 Predation, parasitism, and herbivory

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Competition can occur when resources are

limited

 In competition, multiple organisms seek the same limited resources and all competitors suffer

(/ interaction)

 Food, space, water, shelter, mates, sunlight

 Intraspecific competition  occurs between members of the same species

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limited

 Interspecific competition  occurs between members of two or more species

 Strongly affects community composition  Leads to competitive exclusion or species

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limited

 Competitive exclusion  one species completely excludes another species from using a resource

 Zebra mussels displaced native mussels in the Great Lakes

 Species coexistence  neither species fully

excludes the other from resources, so both live side by side

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Competition can occur when resources are

limited

 Fundamental niche  the full niche of a species

 Realized niche  the portion of the fundamental niche that is actually filled

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limited

 Resource partitioning  process by which species use different resources or use shared resources in different ways

 For example, birds all eating insects, but catching them on different parts of the tree

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Competition can occur when resources are

limited

 Character displacement  competing species diverge in their physical characteristics due to the evolution of traits best suited to the resources they use

 Results from resource partitioning

 Birds that eat larger seeds evolve larger bills

 Birds that eat smaller seeds evolve smaller bills

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Several types of interactions are exploitative

 Exploitation  process by which one member

exploits another for its own gain (/ interactions)  Predation, parasitism, herbivory

 Predation  process by which individuals of one species (predators) capture, kill, and consume individuals of another species (prey)

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Predators kill and consume prey

 Zebra mussels eat phytoplankton and zooplankton  Both populations decrease in lakes with zebra

mussels

 Zebra mussels don’t eat cyanobacteria

 Cyanobacteria increase in lakes with zebra mussels

 Predators may also be prey

 Zebra mussels are being eaten by diving ducks,

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Predators kill and consume prey

 Predator–prey interactions can sometimes drive cyclical population dynamics

 Increased prey population increases predators  Predators survive and reproduce

 Increased predator population decreases prey  Predators starve

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Predators kill and consume prey

 Natural selection leads to evolution of adaptations that make predators better hunters

 Individuals who are better at catching prey:  Live longer, healthier lives

 Take better care of offspring

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Parasites exploit living hosts

 Parasitism  a relationship in which one organism

(parasite) depends on another (host) for nourishment or some other benefit

 The parasite harms, but doesn’t kill, the host

 Some parasites are free-living

 Infrequent contact with their hosts

 Ticks, sea lampreys

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Parasites exploit living hosts

 Parasitoids  insects that parasitize other insects  Lay eggs in larva or adults of other species

 Kill the host

 Coevolution  process in which hosts and parasites become locked in a duel of escalating adaptations

 Has been called an evolutionary arms race

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Herbivores exploit plants

 Herbivory  when animals feed on the tissues of plants

 May not kill the plant, but affects its growth and survival

 Defenses against herbivory include:  Chemicals: toxic or distasteful

 Thorns, spines, or irritating hairs  Other animals: protect the plant

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Mutualists help one another

 Mutualism  relationship in which two or more species benefit from their interactions

 Symbiosis  mutualism in which the organisms live in close physical contact

 Each partner provides a service the other needs (food, protection, housing, etc.)

 Microbes within digestive tracts  Mycorrhizae: plant roots and fungi  Coral and algae (zooxanthellae)

 Pollination  interaction in which bees, bats, birds, and others transfer pollen from one flower to

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Ecological Communities

 Community  an assemblage of populations of

organisms living in the same place at the same time  Members interact with each other

 Interactions determine the structure, function, and species composition of the community

 Community ecologists are people interested in:

 Which species coexist, and how species relate to one another

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Energy passes among trophic levels

 One of the most important species interactions involves who eats whom.

 Matter and energy move through the community

 Trophic level  rank in the feeding hierarchy  Producers (autotrophs)

 Consumers

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Producers

 Producers, or autotrophs (“self-feeders”)  organisms that capture solar energy for

photosynthesis to produce sugars  Green plants

 Cyanobacteria  Algae

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Consumers

 Primary consumers  second trophic level  Organisms that consume producers

 Herbivores consume plants  Deer, grasshoppers

 Secondary consumers  third trophic level  Organisms that prey on primary consumers  Carnivores consume meat

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Consumers

 Tertiary consumers  fourth trophic level  Predators at the highest trophic level

 Consume secondary consumers  Are also carnivores

 Hawks, owls

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Detritivores and decomposers

 Organisms that consume nonliving organic matter enrich soils and/or recycle nutrients found in dead organisms

 Detritivores  scavenge waste products or dead bodies

 Millipedes, soil insects

 Decomposers  break down leaf litter and other

nonliving material into simpler chemicals that can be used by plants

 Fungi, bacteria

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Energy, biomass, and numbers decrease at

higher trophic levels

 Most energy organisms use is lost as waste heat through cellular respiration

 Less and less energy is available in each successive trophic level

 Each level contains only about 10% of the energy of the trophic level below it

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Food webs show feeding relationships and

energy flow

 Food chain  a linear series of feeding relationships

 Food web  a visual map of feeding relationships and energy flow

 Includes many different organisms at all various levels

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Some organisms play outsized roles in

communities

 Community dynamics are complex  Species interactions differ in strength

 Keystone species  a species that has a strong or wide-reaching impact far out of proportion to its

abundance

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Some organisms play outsized roles in

communities

 Trophic cascade  a phenomenon in which predators at high trophic levels indirectly affect populations at low trophic levels

 Predators keep species at intermediate trophic levels in check, allowing growth of species at a lower level  Extermination of wolves led to increased deer

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Communities respond to disturbance in various

ways

 Disturbance  event that causes rapid changes in the environment that alters the community or

ecosystem

 Tree falling, opening space in a forest

 Removal of keystone species, spread of invasive species

 Natural disturbances like tornadoes, hurricanes  Human impacts cause major community changes

 Some species become adapted to disturbance

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Communities respond to disturbance in various

ways

 Communities have different ways of maintaining themselves when disturbed

 Resistance  when a community of organisms resists change and remains stable despite the disturbance

 Resilience  when a community changes in response to a disturbance, but later returns to its original state

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Succession follows severe disturbance

 Succession  the predictable series of changes in a community following a disturbance

 Primary succession  disturbance removes all vegetation and soil life

 Community is built from scratch

 Glaciers, drying lakes, volcanic lava

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Succession follows severe disturbance

 Secondary succession = a disturbance

dramatically alters, but does not destroy, all local organisms

 The remaining organisms and soil form “building blocks” that help shape the process of succession  Fires, hurricanes, farming, logging

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Communities may undergo shifts

 The dynamics of community change are more variable and less predictable than thought

 Competition may inhibit progression to another stage

 Chance factors also affect movement between stages

 Climax community may not be based on climate alone

 Phase (regime) shift  occurs when the overall character of the community fundamentally changes

 Some crucial threshold is passed, a keystone species is lost, or an exotic species invades

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Invasive species pose new threats to

community stability

 Invasive species  non-native (exotic) organisms that spread widely and become dominant in a

community

 Introduced species  species that were deliberately or accidentally brought from elsewhere

 Growth-limiting factors (predators, disease, competitors, etc.) are removed or absent

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We can respond to invasive species through

control, eradication, or prevention

 Techniques to control invasive species  Removing them manually

 Applying toxic chemicals

 Introducing native predators or diseases

 Stressing them with heat, sound, electricity, carbon dioxide, or ultraviolet light

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Altered communities can be restored

 Humans have dramatically changed ecological systems

 Severely degraded systems cease to function

 Ecological restoration  efforts to restore communities

 Restoration is informed by restoration ecology  the science of restoring an area to an earlier

condition to restore the system’s functionality (e.g., filtering of water by a wetland)

 It is difficult, time-consuming, and expensive

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Altered communities can be restored

 Prairie restoration involves replanting native species, controlling invasive species

 Nearly all tallgrass prairie was converted to agriculture by the 19th century

 The world’s largest project is the Florida Everglades  Flood control and irrigation removed water

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Earth’s Biomes

 Widely separated regions share similarities

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Climate influences the location of biomes

 The type of biome depends on abiotic factors

 Temperature, precipitation, soil type, atmospheric circulation

 Climatograph  a climate diagram showing an

area’s mean monthly temperature and precipitation  Similar latitudes have similar climates

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Aquatic and coastal systems resemble biomes

 Various aquatic systems comprise distinct communities

 Coastlines, continental shelves  Open ocean, deep sea

 Coral reefs, kelp forests

 Freshwater lakes and rivers

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Aquatic and coastal systems resemble biomes

 Aquatic systems are shaped by

 Water temperature, salinity, and dissolved nutrients  Wave action, currents, depth, light levels

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Temperate deciduous forest

 Deciduous trees lose their leaves each fall  They remain dormant during winter

 Mid-latitude forests in Europe, eastern China, eastern North America

 Even, year-round precipitation

 Fertile soils

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Temperate grasslands

 More extreme temperature difference between winter and summer than temperate deciduous forest

 Less precipitation

 Also called steppe or prairie

 Once widespread, but has been converted to agriculture

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Temperate rainforest

 Coastal Pacific Northwest

 Great deal of precipitation

 Coniferous trees: cedar, spruce, hemlock, fir

 Moisture-loving animals  Banana slug

 Erosion and landslides affect the fertile soil

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Tropical rainforest

 Southeast Asia, west Africa, Central and South America

 Year-round rain and warm temperatures

 Forest floor is dark and damp

 Lush vegetation

 Diverse species

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Tropical dry forest

 Also called tropical deciduous forest  Plants drop leaves during the dry season

 India, Africa, South America, north Australia

 Wet and dry seasons

 Warm, but seasonal rainfall and less overall than rainforest

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Savanna

 Grassland interspersed with trees

 Africa, South America, Australia, India

 Precipitation is only during the rainy season

 Animals gather near water holes

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Desert

 Minimal precipitation

 Some are bare, with sand dunes (Sahara)

 Some are vegetated (Sonoran)

 They are not always hot

 Temperatures vary widely during the day

 Saline soils

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Tundra

 Russia, Canada, Scandinavia

 Minimal precipitation

 Extremely cold winters

 Extreme variation in day length

 Permafrost  permanently frozen soil  Melting due to climate change

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Boreal forest

 Also called taiga

 Canada, Alaska, Russia, Scandinavia

 Extends for large continuous areas

 A few evergreen tree species

 Cool and dry climate  Long, cold winters  Short, cool summers

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Chaparral

 Occurs in small patches around the globe

 Mediterranean Sea, coastal Chile, California, southern Australia

 Highly seasonal biome  Mild, wet winters

 Warm, dry summers

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Altitudes create patterns analogous to

latitudinal

 Vegetative communities change along mountain slopes

 The climate varies with altitude in the same way it varies with latitude

 A mountain climber in the Andes begins in the tropics and ends on a glacier

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Conclusion

 Biomes and communities help us understand how the world functions

 Species interactions affect communities

 Predation, parasitism, competition, mutualism

 Cause weak and strong, direct and indirect effects

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QUESTION: Review

Mutualism is a form of species interaction where

a) both species are harmed.

b) one species benefits, but the other is harmed.

c) both species benefit.

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QUESTION: Review

Which of the following is NOT an exploitative interaction?

a) Predation

b) Herbivory

c) Parasitism

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QUESTION: Review

An example of resource partitioning is

a) one species eating larger berries and another species eating smaller berries.

b) one species moving out of an area to find new resources.

c) a host species becoming more vulnerable to parasitism.

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QUESTION: Review

Which statement about trophic levels is NOT true?

a) Plants are autotrophs and occupy the first trophic level.

b) Detritivores consume waste products or dead bodies.

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QUESTION: Review

Primary succession would take place on all of the following EXCEPT

a) the slopes of a newly formed volcanic island.

b) a forest in northwest Oregon after it had been logged.

c) a receding glacier.

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QUESTION: Review

Because communities can undergo phase (regime) shifts, we must remember that

a) secondary succession results in a predictable series of stages.

b) we can count on being able to reverse damage caused by human disturbance.

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QUESTION: Review

All of the following are ways to control invasive species EXCEPT

a) removing individuals from the area.

b) stressing them by noise.

c) introducing a predator.

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QUESTION: Review

Which biome has year-round rain and warm temperatures, is dark and damp, and has lush vegetation?

a) Tropical rainforest

b) Temperate grasslands

c) Chaparral

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QUESTION: Review

Which biome is dominated by a few evergreen species, has long, cold winters, and has moose, wolves, bear, and lynx?

a) Tropical rainforest

b) Temperate grasslands

c) Temperate rainforest

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QUESTION: Weighing the Issues

Would you be willing to decrease the amount of meat you consume (i.e., eat lower on the food chain) to

decrease your ecological footprint?

a) Yes, if the extra food was sent to countries with starving people.

b) Yes, because it would decrease environmental degradation.

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QUESTION: Weighing the Issues

Although mustangs are not native to the United States, they exist in several western states on federally owned land. As an introduced species, what should be done with them?

a) As an exotic species, they should immediately be removed and adopted or killed.

b) Although they are an exotic species, they are part of our heritage and should be allowed to stay.

c) They have been here so long, we should just leave them alone.

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QUESTION: Interpreting Graphs and Data

What does this figure illustrate?

a) A predator–prey cycle

b) Competitive exclusion

c) Resource partitioning

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QUESTION: Interpreting Graphs and Data

According to this climatograph for Vaigach, Russia, in the tundra biome, winters are

a) long and warm.

b) short and cool.

c) long and cold.