Learning Objectives. Learning Objectives What are ecosystems? Biomes 11/23/2015

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1 Learning Objectives Be able to explain the following: What are ecosystems? How is weather created? How do energy and chemicals move through Learning Objectives Be able to explain the following: How do species interactions influence the structure of communities? How do communities remain stable or change over time? ecosystems? 15.1 What are ecosystems? A community of biological organisms plus the non-living components with which the organisms interact. Biomes 15.2 A variety of biomes occur around the world, each determined by temperature and rainfall. What is the average temperature? What is the average rainfall (or other precipitation)? Is the temperature relatively constant or does it vary seasonally? Is the rainfall relatively constant or does it vary seasonally? 1

2 Biomes Temperature and precipitation dictate: Primary productivity levels the amount of organic matter produced The numbers and types of primary producers: are the chief determinants of the amount and breadth of other life in the region Global air circulation patterns create deserts and rainforests. 2

3 15.4 Local topography influences the weather. Is it warmer or cooler in urban areas relative to nearby rural areas? Urban Heat Islands Why is it so windy on streets with tall buildings? 15.5 Ocean currents affect the weather. Global patterns of circulation in the oceans 3

4 Why do beach communities have milder weather than more inland communities? Water s capacity to absorb and hold heat Beaches on the east coast of the United States have warmer water than west coast beaches at the same latitudes. Why? 15.6 Energy flows from producers to consumers. 4

5 First Stop: Primary Producers Second Stop: Primary Consumers the Herbivores Third Stop: Secondary Consumers the Carnivores Fourth Stop: Tertiary Consumers the Top Carnivores Chains or Webs? Food chain Pathway from photosynthetic producers through the various levels of animals Food web Involve harvesting energy from multiple stops in the food chain 5

6 Energy Flows Biomass Losses at every step in a food chain Inefficiency of energy transfers 10% rule Where does the rest go? Expended in cellular respiration or lost as feces In humans, why is vegetarianism more energetically efficient than meat-eating? The 10% rule in application 15.8 Essential chemicals cycle through ecosystems. The recycling of molecules 6

7 Chemical Reservoirs Each chemical is stored in a non-living part of the environment. Organisms acquire the chemical from the reservoir. The chemical cycles through the food chain. The Three Most Important Chemical Cycles 1. Carbon 2. Nitrogen 3. Phosphorus Eventually, the chemical is returned to the reservoir. Why are global CO 2 levels rising? Fossil fuels Global CO 2 levels are rising in general, but they also exhibit a sharp rise and fall within each year. Why? 7

8 Nitrogen is like a bottleneck limiting plant growth. Fertilizers 15.9 Interacting species evolve together. Natural Selection Causes organisms to become better adapted to their environment Does not distinguish between biotic and abiotic resources as selective forces Each species role in a community is defined by its niche. 8

9 More than just a place for living, a niche is a complete way of living. You can t always get what you want. Fundamental niche the full range of environmental conditions under which a species can live Realized niche where and how a species is actually living Competition can be hard to see, but it still influences community structure. Predation One of the most important forces shaping the composition and abundance of species in a community 9

10 Prey Adaptations for Reducing Predation Why do exotic species often flourish when released into novel habitats, even though natural selection has not adapted them to this new environment? There are two broad categories of defenses against predators: Physical Behavioral Physical Defenses Include mechanical, chemical, warning coloration, and camouflage mechanisms 1. Mechanical Defenses 2. Chemical Defenses 10

11 3. Warning Coloration 4. Camouflage Behavioral defenses Include both seemingly passive and active behaviors: hiding or escaping, or alarm calling or fighting back Predator adaptations for enhancing predation 11

12 Why don t predators become so efficient at capturing prey that they drive the prey to extinction? Parasitism is a form of predation. The life-dinner hypothesis Parasite Predators Parasites have some unique features and face some unusual challenges: The parasite generally is much smaller than its host and stays in contact with the host for extended periods of time. Complicated life cycles as means of getting from host to host. Case 1: Parasites can induce foolish, fearless behavior in their hosts. Case 2: Parasites can induce inappropriate aggression in their hosts. Toxoplasma Rats and cats 12

13 Case 3: Parasites can induce bizarre and risky behavior in their hosts. The lancet fluke Not all species interactions are negative: mutualism and commensalism Communities can change or remain stable over time Many communities change over time. 13

14 Secondary Succession Much faster than primary succession life and soil are already present Some species are more important than others within a community. 14