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Explore the relationship between weather and climate, the greenhouse effect, the impact of latitude on climate, biotic and abiotic factors, community interactions, and ecological succession in this informative chapter.
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Chapter 4 Ecosystems and Communities
Weather vs. Climate • Weather: day to day condition of Earth’s atmosphere at a particular time and place. • Climate: refers to the average, year-after-year conditions of temperature and precipitation in a particular region.
The Greenhouse Effect • Carbon dioxide, methane, water vapor, and a few other greenhouse gases trap heat energy and maintain Earth’s temperature range. • These gases trap the heat energy of sunlight inside earth’s atmosphere. • This process is known as the greenhouse effect. • If these gases were not present in the atmosphere, Earth would be 30°C cooler than it is today.
The Effect of Latitude on Climate • Latitude: the distance north or south of the equator of a point on the earth's surface. • The equator receives the most direct sunlight. • As a result of differences in latitude and thus the angle of heating, Earth has 3 main climate zones: • Polar • Temperate • Tropical
Polar Zones • Cold areas where the sun’s rays strike Earth at a very low angle. • These zones are located in the areas around the north and south poles, between 66.5° and 90° North and South latitudes.
Temperate Zones • Sit between the polar and tropical zones. • These zones are characterized by a change in temperature over the course of a year. • The reason: they are more affected by the changing angle of the sun causing ranges in heat from hot to cold, depending on the season.
Tropical Zone • Located near the equator between 23.5° North and 23.5° South latitudes. • The tropics receive direct or nearly direct sunlight year-round, making the climate almost always warm.
What shapes and ecosystem? • Biotic and Abiotic Factors • The Niche • Community Interactions • Ecological Succession
Biotic and Abiotic Factors • Biotic factors: the biological influences on organisms within an ecosystem. • The ecological community • Abiotic factors: physical, or nonliving, factors that shape ecosystems. • Temperature • Precipitation • Humidity • Nutrient Availability • The biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which the organism lives: habitat.
The Niche • A niche is the full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions. • An organism’s niche includes: • Type of food • How it obtains food • Which other species use the organism as food.
Community Interactions • Competition • Predation • Symbiosis
Competition • Competition: when organisms of the same or different species attempt to use an ecological resource in the same place and at the same time. • Resource: any necessity of life. • Competitive exclusion principle: states that no two species can occupy the same niche in the same habitat, at the same time.
Predation • Predation: an interaction in which one organism captures and feeds on another organism. • Predator: the organism that does the killing and eating. • Prey: the organisms that is eaten.
Symbiosis • Symbiosis: any relationship in which two species live closely together. • 3 main classes of symbiosis: • Mutualism: both species benefit. • Termite and protist • Commensalism: one species benefits and the other is not affected • Barnacles and whales • Parasitism: one species benefits and the other is harmed • Tapeworm and pig
Ecological Succession • Ecosystems are constantly changing in response to natural and human disturbances. • As an ecosystem changes, older inhabitants naturally die out and new organisms move in, causing further changes in the community. • This series of predictable changes that occurs in a community over time is called ecological succession.
There are 2 Types of Ecological Succession • Primary Succession • Secondary Succession
Primary Succession • Occurs on land where no soil exists. • Ex: Occurs on the surfaces formed as volcanic eruptions build new islands or cover the land with lava rock or volcanic ash. • When it begins there is no soil, just ash and rock. • The first species to populate the area are called pioneer species. • The pioneer species on volcanic rock are often lichens. • Lichens are organisms that are formed from the mutualistic relationship between algae and fungi. • As they grow they break up the rock. • When they die they add organic matter to help form the soil on which plants can grow.
Secondary Succession • Follows a disturbance that changes an existing community without removing soil. • Occurs when land cleared for farming or mining is abandoned, or when wildfires burn woodlands. • Certain plants have adapted to a regular cycle of fire and re-growth. • Their seeds won’t sprout unless exposed to fire.
Biomes • A biome is a complex of terrestrial (land) communities that covers a large area and is characterized by certain soil and climate conditions.
There are at least 9 biomes scientists recognize: Tropical rain forest Tropical dry forest Tropical savanna Temperate grassland Desert Temperate woodland and shrubland Temperate forest Northwest coniferous forest Boreal forest (taiga) Tundra The Major Biomes
Aquatic Ecosystems • Aquatic ecosystems are determined primarily by the depth, flow, temperature, and chemistry of the overlying water. • There are 3 categories of aquatic ecosystems: • Freshwater • Estuaries • Marine ecosystems
Freshwater Ecosystems • Flowing-Water Ecosystems • Standing-Water Ecosystems • Freshwater Wetlands
Flowing-Water Ecosystems: • Rivers, streams, creeks, and brooks • Organisms that live there are well-adapted to the rate of flow.
Standing-Water Ecosystems: • Lakes and ponds • Relatively still waters provide habitats for many organisms that would be quickly washed away in flowing water:
Freshwater Wetlands: • An ecosystem in which water either covers the soil or is present at or near the surface of the soil for at least part of the year. • Bogs, marshes, swamps
Estuaries • Wetlands formed where rivers meet the sea. • They contain a mixture of freshwater and salt water. • Examples: • Salt Marshes: temperate-zone dominated by salt-tolerant grasses above the low-tide line, and by sea-grasses underwater. • Mangrove Swamps: coastal wetlands that are found in tropical regions, including southern Florida (everglades) and Hawaii. • The Dominant plants are salt-tolerant trees, collectively called mangroves.
Marine Ecosystems • Zones based on depth: • Photic zone: well-lit upper layer of the ocean, where photosynthesis can occur (depth of about 200 meters). • Aphotic zone: below the photic zone, permanently dark area where only chemosynthetic autotrophs are the producers. • Zones based on distance from the shore and depth: • Intertidal zone • Coastal zone • Open Ocean
Intertidal Zone • Organisms in the intertidal zone are exposed to regular extreme changes in their surroundings. • Once or twice a day they are submerged in seawater, while the remainder of the time they are exposed to sunlight, air, and temperature changes. • There are many different types of intertidal communities.
Coastal Ocean • Extends from the low-tide mark to the outer edge of the continental shelf, the relatively shallow border that surround continents. • The continental shelf is often shallow enough to fall mostly or entirely in the photic zone, so photosynthesis can occur throughout this depth. • Kelp forests: a collection of giant brown alga (seaweed) that can grow as quickly as 50 cm/day. • Coral Reefs: found in the warm, shallow water of tropical coastal oceans.
Open Ocean (Oceanic Zone) • Begins at the edge of the continental shelf and extends outward. • It is the largest marine zone. • Ranges about 500 m deep – > 11,000 m • Organisms in the deep ocean are exposed to high pressure, frigid temperatures, and total darkness. • Benthic zone: ocean floor
