Biodiversity, Species Interactions, and Population Control Chapter 5

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 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)

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

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

(d) Foul-tasting monarch butterfly (e) Poison dart frog Fig. 5-2, p. 103 Stepped Art (h) When touched, snake caterpillar changes shape to look like head of snake. (a) Span worm(b) Wandering leaf insect (c) Bombardier beetle (f) Viceroy butterfly mimics monarch butterfly (g) Hind wings of Io moth resemble eyes of a much larger animal. Some Ways Prey Species Avoid Their Predators

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

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

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?

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

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.

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

Fig. 5-8, p. 107 Cape May Warbler Stepped Art Blackburnian Warbler Black-throated Green Warbler Yellow-rumped Warbler Bay-breasted Warbler Sharing the Wealth: Resource Partitioning

Fig. 5-9, p. 108 Kona Grosbeak Fruit and seed eatersInsect and nectar eaters Kuai Akialaoa Amakihi Crested Honeycreeper Apapane Unkown finch ancestor Maui Parrotbill Akiapolaau Greater Koa-finch Specialist Species of Honeycreepers

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

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.

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

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

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.

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

Environmental resistance  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

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

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

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.

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

Fig. 5-16, p. 116 Time Exposed rocks Lichens and mosses Small herbs and shrubs Heath mat Jack pine, black spruce, and aspen Balsam fir, paper birch, and white spruce forest community Primary Ecological Succession

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

Fig. 5-17, p. 117 Time Annual weeds Perennial weeds and grasses Shrubs and small pine seedlings Young pine forest with developing understory of oak and hickory trees Mature oak and hickory forest Natural Ecological Restoration of Disturbed Land (secondary)

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