Community ecology. Communities and Ecosystems. Foothill (or oak) woodland community. Natural Communities of the San Francisco Peninsula

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1 Community ecology Communities and Ecosystems Chapter 20 Community ALL the organisms (plants, animals, fungi, microbes) that live in a particular area Community ecology focuses on interactions between species Natural Communities of the San Francisco Peninsula Chaparral Redwood forest Foothill oak woodland Chaparral Grassland Urban bay Communities are identified by the dominant species (usually a plant) Foothill (or oak) woodland community Found at lower elevations along the coast and interior valleys Dominant plants are oaks Many are deciduous Acorns provide food for many animals, from acorn woodpeckers to deer Diversity of habitats Ranges from open savannah to dense forest with a welldeveloped understory Adaptations of Oaks The California Buckeye a toxic beauty Common in areas with summer drought Water-conserving strategies leathery leaves covered with a waxy layer to prevent drying out Deciduous: leaves shed when water is scarce; leaf out during winter/spring rains Developed toxins to discourage herbivores e.g. tannins in acorns Adaptations Grows during wet winter and spring months Drops its leaves in midsummer, goes dormant The bark, leaves and fruit (buckeyes) contain a neurotoxin The Ohlone used the poisonous nuts to stupefy fish to make them easier to catch

2 Species diversity: Acorn woodpecker Melanerpes formicivorus Complicated social system Live in extended family groups Up to 7 breeding males and 3 breeding females in one group. All family members spend lots of time storing acorns in holes drilled into a single tree, the granary tree. Dusky-footed woodrat Neotoma fuscipes Large ears and hairy tails Build large stick houses on ground or in trees Houses include several rooms: nesting, resting, storing food and other treasures Pick up shiny objects (packrats) Reproduction: usually more than 1 litter per year, breeds throughout the year Predators: owls, coyotes, skunks, bobcats What is Sudden Oak Death? A plant disease threatening coastal forests in California and Oregon Caused by an exotic (nonnative) microbe, Phytophthora ramorum Over a million tanoak and oak trees in California have been killed There is no known cure A very different community: Redwood forest In fog-prone canyons or slopes Climate: moist, mild temperature Along coast of CA Redwoods can live for >1000 yrs and are the world s tallest trees (>300 ft) Under-story of Western sword fern, redwood sorrel Common animals: stellar jay, chickadee, banana slug Source: California Oak Mortality Task Force The redwood community Community ecology Study of the interactions between species in a community form over time Some are products of coevolution Co-evolution An adaptation in one species leads to an counter-adaptation in another species

3 Pollination: An example of co-evolution Many flowers have coevolved with the animals that pollinate them to improve pollen transfer Bats are nocturnal Bat-pollinated flowers are white, smell like bats, and large and sturdy Flowering plants and their pollinators have co-adapted Hummingbirds are attracted to red flowers, a color they can see The flower s petals are curved to allow the stamens to dust the bird s heads Note the pollen on the beak and head Hidden beauty of pollination TED start at 3:15 (7:40) Interactions in communities Avoiding competition Species compete for resources One feeds on another (predator-prey) Both species can benefit Each species occupies a position in the community Lives in a particular area or habitat Plays a role: photosynthesizer, predator, prey, decomposer Interacts with other species Called its ecological niche Black necked stilt Metamorphosis A marvel of nature Larval stages specialized for eating and growing (e.g. caterpillars) Adaptations of Monarch butterflies Monarch butterfly The adult is specialized for dispersal and reproduction Metamorphosis (changing shape) from larva to adult occurs during the pupal stage

4 Co-evolution: the Monarch and the milkweed The milkweed plant produces a toxin to protect itself from insects. The Monarch caterpillar is able to counter the toxins and stores them up in its body. Mimicry Monarch butterfly poisonous warning coloration Viceroy butterfly Coevolution harmless The adult butterfly tastes bad, and birds learn not to eat them. not related to the Monarch, but looks a lot like it. Predators avoid them too. Monarch migration Monarchs can t survive cold winter temps, so they migrate south and hibernate (rest with a very slow heart rate). Monarchs east of the Rocky Mountains migrate 2500 miles to central Mexico. Monarchs west of the Rocky Mountains have a shorter migration to their roosting areas on the California coast Monarchs hibernating Clump of Monarchs over-wintering in the trees in Santa Cruz and Pacific Grove (near Monterey) Visit Natural Bridges State Park this winter (roughly Oct to May) 4 min Members of a community interact in different ways Competition ( / ) Predation (+/ ) Parasitism (+/ ) Mutualism (+/+) Competition between species Two species compete for limited resources Food Water Space Generally has a negative effect on the abundance of both species ( / ) Lion and hyena

5 Defensive Coloration Predation (+/ ) One species (the predator) kills and eats the other (the prey) Predation is a key factor in evolution Eating and avoiding being eaten are prerequisites to reproductive success Cryptic coloration Where s the inchworm? Warning coloration This frog advertises its toxicity Plant defenses against predation (+/ ) Mimicry A copycat adaptation in which one species looks like another Spines and thorns Chemicals that make them toxic to herbivores Scarlet king snake Eastern coral snake NOT venomous Nicotine produced by tobacco plants Tannins in oaks Venomous Parasitism (+/ ) Mutualism (+/+) One organism benefits, the other is harmed The parasite obtains its nutrients by living on or in its host organism Internal parasites External parasites Both species benefit Tapeworms the protozoa that causes malaria Ants eat the honeydew that aphids excrete and protect the aphids from predators. Mosquitoes, fleas suck blood from animals Aphids suck the sap of plants Pollination is a classic example of mutualism

6 What is an ecosystem? Example of an ecosystem All the organisms in an area plus the physical environment Plants, animals, fungi, microorganisms Soil, water, air Includes both living and non-living things Estuary Where fresh water meets the ocean One of the most productive ecosystems in the world Home to more than 2/3 of the fish and shellfish consumed by humans. Rich in decomposers that convert organic nutrients into their chemical components Fragile ecosystems Estuaries One of the most biologically productive environments on Earth Lots of nutrients Feeding areas for birds Important nursery and protective habitats for juvenile fish, including salmon Saving the bay Episode 1 3:25 The Sacramento Delta the largest estuary on the west coast of N and S America The Sacramento Delta is in a state of ecological collapse The Sacramento and the San Joaquin Rivers join to form a huge estuary 2/3 of Californians get their drinking water from the Delta. Silicon Valley, Central Valley farmers and Los Angeles. Are we removing too much water? a nosedive in the population of delta smelt, salmon, and other fish species Other stressors: invasive clams, contamination from sewage plants and other sources Energy flow in ecosystems Food chains: feeding relationships Heat Sun = source of energy Plants and algae convert the solar energy into food energy Energy is used for life functions growth, movement, reproduction Energy is lost as it passes through an ecosystem Living organisms lose energy as heat The species of a community are divided into different trophic levels based on their main sources of nutrition Producers Consumers Herbivores Carnivores Decomposers

7 What limits the length of food chains? Energy loss in ecosystems Most of the energy captured by plants is lost as energy passes through the food chain Only 10-15% of the calories an herbivore eats become stored as body mass available to the next link in the food chain. Only a small % of nutrients consumed by lower-level consumers (herbivores) is available to higherlevel consumers An energy pyramid is a diagram that shows the cumulative loss of energy from a food chain. Energy flow applies to the human population Eating producers instead of consumers reduces our impact on the environment Chemicals Cycle in Ecosystems Energy flows through ecosystems Eventually lost as heat But the chemicals that life requires (carbon, water, nitrogen, etc) are recycled These chemicals cycle from the environment to living organisms and back again Figure The Carbon Cycle Carbon cycles between the atmosphere and living organisms The atmosphere is the reservoir for carbon (CO 2 gas) Plants convert the CO 2 into food by photosynthesis Cellular respiration returns CO 2 to the atmosphere Burning fossil fuels is steadily raising the level of CO 2 in the atmosphere