Biodiversity, Species Interactions, and Population Control Chapter 5

Southern Sea Otter

Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? Habitat Hunted: early 1900s Partial recovery by the late 2007

Why care about them?

Why care about sea otters? Ethics Keystone species (Eat sea Urchins) Tourism dollars

Science Focus: Why Should We Care about Kelp Forests? Kelp forests: one of the most biologically diverse marine habitat One blade of kelp can grow 2 feet in a single day Major threats to kelp forests Sea urchins Pollution from water run-off Global warming (changing of the water’s temp)

Purple Sea Urchin

Video: Kelp forest (Channel Islands)

Video: Coral spawning

5-1 How Do Species Interact? Concept 5-1 Five types of species interactions—competition, predation, parasitism, mutualism, and commensalism—affect the resource use and population sizes of the species in an ecosystem.

Species Interact in Five Major Ways Interspecific Competition: over same resources Predation Parasitism: one gains, one loses (not always death) Mutualism: both gain Commensalism: one gains, the other gets no benefits

Interspecific Competition

Most Species Compete with One Another for Certain Resources Competition for same limited resources (food, shelter, space) Competitive exclusion principle: no 2 species can occupy exactly the same ecological niche for very long

Most Consumer Species Feed on Live Organisms of Other Species (1) Predators may capture prey by Walking Swimming Flying Pursuit and ambush Camouflage Chemical warfare

Most Consumer Species Feed on Live Organisms of Other Species (2) Prey may avoid capture by Camouflage Chemical warfare Warning coloration Mimicry Deceptive looks Deceptive behavior

Some Ways Prey Species Avoid Their Predators (a) Span worm (b) Wandering leaf insect Some Ways Prey Species Avoid Their Predators (c) Bombardier beetle (d) Foul-tasting monarch butterfly (e) Poison dart frog (f) Viceroy butterfly mimics monarch butterfly Figure 5.2 Some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior. (g) Hind wings of Io moth resemble eyes of a much larger animal. (h) When touched, snake caterpillar changes shape to look like head of snake. Stepped Art Fig. 5-2, p. 103

Video: Salmon swimming upstream

Predator and Prey Species Can Drive Each Other’s Evolution Intense natural selection pressures between predator and prey populations Coevolution

Coevolution: A Langohrfledermaus Bat Hunting a Moth

Predation

Video: Otter feeding

Some Species Feed off Other Species by Living on or in Them Parasitism Parasite-host interaction may lead to coevolution Host’s point of view: parasites bad Population level POV: promote biodiversity, keep populations in check

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

Parasitism Ticks

In Some Interactions, Both Species Benefit Mutualism Nutrition and protection relationship Gut inhabitant mutualism: vast armies of bacteria, break down food How is a Cow like a termite? Cooperation between species?

Mutualism

Mutualism: Oxpeckers Clean Rhinoceros; Anemones Protect and Feed Clownfish

Centipede

In Some Interactions, One Species Benefits and the Other Is Not Harmed Commensalism Epiphytes Birds nesting in trees Army ants and silverfish

Commensalism: Bromiliad Roots on Tree Trunk Without Harming Tree

Chapter 5, section 1 Q1: What are the 5 different ways that species interact with each other? Give an example of each. Describe what is unique about each interaction type. Q2: Describe a trait possessed by the southern sea otter that helps it a) catch prey and b) avoid being preyed upon Q3: Compare Competitive exclusion principle with coevolution

Q5: Why would detritus feeders and decomposers not considered predators? Q6: What methods/ways help predators catch their prey? Q7: What ways have the prey developed to avoid being caught? Q9: Why can coevolution be described like an arms race? Q10: Explain how each of the species interactions can affect the population sizes of species in ecosystems.

5-2 How Can Natural Selection Reduce Competition between Species? Concept 5-2 Some species develop adaptations that allow them to reduce or avoid competition with other species for resources.

Question Do species want to compete for niche space?

Some Species Evolve Ways to Share Resources Resource partitioning Reduce niche overlap, increase species diversity Use shared resources at different Times Places Ways

Competing Species Can Evolve to Reduce Niche Overlap

Sharing the Wealth: Resource Partitioning Blackburnian Warbler Black-throated Green Warbler Cape May Warbler Bay-breasted Warbler Yellow-rumped Warbler Figure 5.8 Sharing the wealth: resource partitioning of five species of insect-eating warblers in the spruce forests of the U.S. state of Maine. Each species minimizes competition for food with the others by spending at least half its feeding time in a distinct portion (shaded areas) of the spruce trees, and by consuming different insect species. (After R. H. MacArthur, “Population Ecology of Some Warblers in Northeastern Coniferous Forests,” Ecology 36 (1958): 533–536.) Stepped Art Fig. 5-8, p. 107

Insect and nectar eaters Fruit and seed eaters Insect and nectar eaters Greater Koa-finch Kuai Akialaoa Specialist Species of Honeycreepers Amakihi Kona Grosbeak Crested Honeycreeper Akiapolaau Figure 5.9 Specialist species of honeycreepers. Evolutionary divergence of honeycreepers into species with specialized ecological niches has reduced competition between these species. Each species has evolved a beak specialized to take advantage of certain types of food resources. Maui Parrotbill Apapane Unkown finch ancestor Fig. 5-9, p. 108

Honey creepers on Hawaii Evolved into different species, each concentrating on different food resources Evolutionary divergence-speciation

Chapter 5, section 2 questions Q11: How does resource partitioning increase species diversity? Q12: How did the warblers reduce competition when eating insects on spruce trees? Q13: How is the evolutionary progress of honey creepers an example of evolutionary divergence?

Question How many humans can live on the Earth? How many cockroaches?

5-3 What Limits the Growth of Populations? Concept 5-3 No population can continue to grow indefinitely due to: limitations on resources competition among species for those resources.

What information can be used to describe the differences between 2 different populations of the same creature?

Populations Have Certain Characteristics (1) Populations differ in Distribution Numbers Age structure These values are Population dynamics

Populations Characteristics can change due to: Temperature change Presence of disease, organisms or harmful chemicals Resource availability Arrival or disappearance of competing species

Population distributions

Most Populations Live Together in Clumps or Patches (1) Different types of population distribution: Clumping Uniform dispersion (what would cause this?) Random dispersion (what would cause this?)

Most Populations Live Together in Clumps or Patches (2) Why clumping? Species tend to cluster where resources are available Groups have a better chance of finding clumped resources Herds protect some animals from predators Packs allow some predators to get prey Temporary groups for mating and caring for young

Why does the population of the US continues to increase, despite the birthrate falling below 2.0 kids per mother?

Populations Can Grow, Shrink, or Remain Stable (1) Population size governed by Births Deaths Immigration Emigration Population change = (births + immigration) – (deaths + emigration)

Populations Can Grow, Shrink, or Remain Stable (2) Age structure Pre-reproductive age Reproductive age (if greatest %, greatest growth) Post-reproductive age Excluding emigration/immigration, a population that has an even distribution amongst the groups will remain stable.

How would you describe the US population, in terms of age? Pre-reproductive Reproductive Post-reproductive

Population Growth Rates Biotic potential: capacity for pop growth Low (elephants, whales) High (insects and bacteria) Intrinsic rate of increase (r) Steepness of curve Individuals in populations with high r Reproduce early in life Have short generation times (adaptable) Can reproduce many times Have many offspring each time they reproduce

Better than roaches and bunnies A species of bacteria could carpet the entire surface of the earth 1 foot deep in 36 hours, if there was nothing to control its population numbers. What stops it from doing so?

Environmental resistance Combo of all factors which limit growth Size of populations limited by Light Water Space Nutrients Exposure to too many competitors, predators or infectious diseases

No Population Can Grow Indefinitely: J-Curves and S-Curves (3) Carrying capacity (K) Max population sustained indefinitely Exponential growth (j-curve) (even 1-2% growth is exponential) Logistic growth (s-curve) Rapid growth followed by leveling off

The first part of any population graph should be a J As population nears carrying capacity, graph should change into an s-curve

No Population Can Continue to Increase in Size Indefinitely

Logistic Growth of a Sheep Population on the island of Tasmania, 1800–1925

When a Population Exceeds Its Habitat’s Carrying Capacity, Its Population Can Crash Carrying capacity: not fixed, dependent on environmental factors (food, conditions) Reproductive time lag may lead to overshoot Dieback (crash) Overshoot Damage may reduce area’s carrying capacity

Science Focus: Why Are Protected Sea Otters Making a Slow Comeback? Low biotic potential Prey for orcas Cat parasites (from kitty liter flushed) Thorny-headed worms (seabirds) Toxic algae blooms (urea, fertilizer) PCBs and other toxins Oil spills

Population Size of Southern Sea Otters Off the Coast of So Population Size of Southern Sea Otters Off the Coast of So. California (U.S.)

Exponential Growth, Overshoot, and Population Crash of a Reindeer

Story of the Reindeer 26 introduced to island in Bering Sea No predators, pop soared Food is slow growth lichens and mosses Pop starved, crashed to 8 in 1950

Species Have Different Reproductive Patterns r-Selected species, opportunists Capacity for high rate of pop increase Little or no care of offspring Large populations K-selected species, competitors Reproduce later in life Long life spans Small number of offspring, care Small Populations

Positions of r- and K-Selected Species on the S-Shaped Population Growth Curve

Genetic Diversity Can Affect the size, success of Small Populations Founder effect: few individuals start new colony Demographic bottleneck: few individuals survive catastrophe Genetic drift: random changes to gene frequencies in pop that lead to unequal reproductive success Inbreeding: increase of defective genes in small pop Use above to estimate minimum viable population size

Population Density and Population Size Density independent pop controls Mostly abiotic like weather, forest fires… Density-dependent population controls Predation Parasitism Infectious disease Competition for resources

Several Different Types of Population Change Occur in Nature Stable Irruptive: external conditions (temp…) Cyclic fluctuations, boom-and-bust cycles (more than once, internal) Top-down population regulation (bunnies-lynx) Bottom-up population regulation (lemmings) Irregular (no drastic increases)

Population Cycles for the Snowshoe Hare and Canada Lynx (notice general delay in lynx crashes)

Humans Are Not Exempt from Nature’s Population Controls Ireland Potato crop in 1845 Bubonic plague Fourteenth century AIDS Global epidemic

Questions on 5.3 Q15: Why do populations tend to live in clumps? Q17: What are the 3 age group categories in a population’s age structure Q21: Which group grasshoppers or elephants have a high biotic potential? Why? Q25: Use the concepts of carrying capacity to explain why there are always limits to population growth in nature Q30: Distinguish between r-selected species and k-selected species and give an example of each type. Which are humans?

White-tailed deer

Case Study: Exploding White-Tailed Deer Population in the U.S. 1900: deer habitat destruction and uncontrolled hunting 1920s–1930s: laws to protect the deer Results of current population explosion for deer Lyme disease Deer-vehicle accidents Eating garden plants and shrubs Ways to control the deer population

Solutions to the consequences of the exploding deer population List at least 3 different solutions that would result in a sustainable deer population. (several in textbook or come up with your own For each solution, describe: The economic and environmental cost Changes in the population dynamics over time Main causes for change in the carrying capacity for deer

Modeling population growth lab Vernier

5-4 How Do Communities and Ecosystems Respond to Changing Environmental Conditions? Concept 5-4 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession.

Mt. St. Helens-Secondary Succession

Primary Succession Candidate

Candidates for primary succession

Communities and Ecosystems Change over Time: Ecological Succession Natural ecological restoration Primary succession Starts from bare rock Secondary succession Does not start from bare rock New home construction (why?)

Some Ecosystems Start from Scratch: Primary Succession No soil in a terrestrial system No bottom sediment in an aquatic system Early successional plant species, pioneer Midsuccessional plant species Late successional plant species

Primary Ecological Succession Figure 5.16 Primary ecological succession. Over almost a thousand years, plant communities developed, starting on bare rock exposed by a retreating glacier on Isle Royal, Michigan (USA) in northern Lake Superior. The details of this process vary from one site to another. Question: What are two ways in which lichens, mosses, and plants might get started growing on bare rock? Balsam fir, paper birch, and white spruce forest community Jack pine, black spruce, and aspen Heath mat Small herbs and shrubs Lichens and mosses Exposed rocks Time Fig. 5-16, p. 116

Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (1) Some soil remains in a terrestrial system Some bottom sediment remains in an aquatic system Ecosystem has been Disturbed Removed Destroyed

Natural Ecological Restoration of Disturbed Land (secondary) Figure 5.17 Natural ecological restoration of disturbed land. Secondary ecological succession of plant communities on an abandoned farm field in the U.S. state of North Carolina. It took 150–200 years after the farmland was abandoned for the area to become covered with a mature oak and hickory forest. A new disturbance, such as deforestation or fire, would create conditions favoring pioneer species such as annual weeds. In the absence of new disturbances, secondary succession would recur over time, but not necessarily in the same sequence shown here. Questions: Do you think the annual weeds (left) would continue to thrive in the mature forest (right)? Why or why not? See an animation based on this figure at CengageNOW. Mature oak and hickory forest Young pine forest with developing understory of oak and hickory trees Shrubs and small pine seedlings Perennial weeds and grasses Annual weeds Time Fig. 5-17, p. 117

Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (2) Primary and secondary succession Tend to increase biodiversity Increase species richness and interactions among species Primary and secondary succession can be interrupted by Fires Hurricanes Clear-cutting of forests Plowing of grasslands Invasion by nonnative species

Factors that affect the rate of succession Facilitation: one set of species makes area makes area suitable for following species, less for themselves (mosses/lichens and grasses) Inhibition: hinder establishment and growth of species ex: pine trees Tolerance: unaffected by plants in earlier stages (mature trees vs shade plants)

Succession Doesn’t Follow a Predictable Path Traditional view Balance of nature and a climax community Achieves equilibrium Current view Succession Doesn’t follow a predictable path Ever-changing mosaic of patches of vegetation Mature late-successional ecosystems State of continual disturbance and change, not permanent equilibrium

Living Systems Are Sustained through Constant Change Inertia, persistence Ability of a living system to survive moderate disturbances Resilience Ability of a living system to be restored through secondary succession after a moderate disturbance Tipping point

Tropical Rain Forest Ecosystem is persistent but is not resilant

Arthropod biodiversity lab

UN project Questions Give 2 examples of r-selected and k-selected species that live in your country Obtain a picture of a park or wilderness area of your country. Where in terms of ecological succession (early, mid, late, climax) does your picture represent? State evidence to support your choice Indicate specific examples from your country for the following, (avoid examples that could show up globally): a) Interspecific competition b) Predator and Prey c) Parasite and host d) Mutualism e) Commensalism f) For each example given describe the population distribution pattern