2Homeostasis in Communities Changing with the EnvironmentEcosystems are always changing.Changing conditions affect communities.There are patterns to these changes that helps us understand how ecosystems developed.
3Limiting factorsLimiting factors: any biotic or abiotic factor that restricts the existence, numbers, reproduction, or distribution of organisms.Remember that effects on one population have indirect effects on other populations within the community.
4Ranges of toleranceTolerance: the ability to withstand fluctuations in biotic and abiotic environmental factors.Some species can tolerate conditions that other species cannot.
5Seccession: A Change in Communities over Time Seccession: orderly, natural changes that take place in the community of an ecosystem.Primary Succession: the colonization of new sites by communities of organismsE.g. lava forming new land, silt creating new soil
7Pioneer plants create soil Pioneer plants die and decay adding their nutrients to the raw environment and lay the foundation for soil.Once soil is present it is possible for small weedy plants, ferns and insects to move in. More plants die and add to the increasing amount of soil.Eventually a climax community is achieved.
8Climax communityClimax community: a stable mature community that undergoes little or no succession.The climax community represents the combination of plants and animals which make the most efficient use of available resources and conditions. In other words, the community established by nature is the one which works best given the climate, topography and other characteristics of the area.
10Secondary successionSecondary succession: the sequence of community changes that takes place when a community is disrupted by natural disasters or human actions.Since the soil is already in place, secondary succession can take place five to ten times faster than primary succession.
11Secondary seccession (cont) When a community is significantly disturbed, the loss of the vegetation may change the abiotic conditions. If this occurs and the habitat has changed, secondary succession may lead to a different climax community.An example is the tropical rain forest. The forest "creates" the rainfall through the process of transpiration. When the trees are removed, the rainfall stops. The land then becomes arid. The resulting new climax community is often desert shrubs
12Example of human interference with succession- 1. Producing a lawn means a constant battle against natural 2. What you must do to maintain such a systema. plant grass seed- competition against natural seed dispersalb. mow- limits the establishment of trees and other tall species c. apply herbicides- to eliminate interspecific competition and to cut down on species diversity-d. apply fertilizer- grass species use up soil nutrients quickly e. irrigate- natural rainfall is often inadequate for lawn grass f. apply fungicides and other chemicals to control disease and insect pests- must be done because an unnatural ecosystem is more prone to disruption3. Thus, when humans interfere with plant communities -> many problems that would be controlled in a natural system (this same thing happens in farming) 4. Without the continued interference of humans, the yard would have a natural sequence of succession over time
13Example: secondary succession on abandoned farm in Maryland 1. Annuals (weeds like crabgrass) 1-2 years 2. Perennials (herbs and tall grasses) 2-5 years3. Young pine seedlings in tall grass 5-10 years 4. Pine forest years5. Deciduous hardwood forest (climax) 150+ years
17Aquatic Biomes: Life in the Water Biome: a large group of ecosystems that share the same type of climax community.75% of earth’s surface is covered with water.Most are marine.Fresh water is confined to rivers, streams, ponds, and most lakes.
19Marine BiomesLife began in the ocean billions of years ago. Most of the life forms which currently occupy the earth had their start as single-celled organisms, forced into evolution by an ever-changing environment.
20Ecologist often separate marine biomes Shallow, sunlit zones called the photic zone. They exist along coast lines (coastal ecosystems).Unlighted zones: aphotic zone
21Another way to divide The marine regions can also be divided into coral reefsEstuariesoceans
22Coral ReefsIn the warm shallow waters which line the continents and surrounding islands lie barriers called coral reefs.Coral is a living organism consisting of animal and algae tissues. The coral reef is also host to other species such as starfish, octopi, and other mollusks.
23EstuariesEstuary: A costal body of water partially surrounded by land in which fresh water and salt water mix.Salinity in the estuarychanges with the tideand contain salt marshecosystems.
24Intertidal ZoneThe portion of the shoreline that lies between high and low tide lines is called the intertidal zone.
25Coasts Because of rising and falling tides, coastal areas are constantly changing, with various animals and marine plants living at the bottom, and on the seashore. Rocky coastal areas are host to fewer species.
26Ocean The Pelagic zone: Out in the open ocean (photic) host to many species of fish and marine mammals, plankton ,and some floating seaweed. is called sargasum.The Benthic zone: deep-sea (aphotichost to silt, sand, and slowly decomposing organisms. This area is very cold because of its depth. There are few plants at this level, and the animals include mostly bottom feeding organisms such as starfish, anemones, sponges, amongst others, as well as various micro-organisms.
27Oceans cont. Abyssal zone: the deepest part of the ocean host to many species of invertebrates and fish including such oddities as the coelacanth, a prehistoric fish once thought extinct, and other fish that bioluminescence. The abyssal zone is very cold, and highly pressurized. Its floor features thermal vents formed by spreading tectonic plates which release hydrogen sulfide (H2S) and other minerals which are consumed by bacteria that form the bottom of the food web.
28Terrestrial Biomes Include: The TundraTaiga (coniferous forests)The Temperate ForestsDesertsGrasslands
29There are 2 types of Tundra The TundraThere are 2 types of TundraArctic tundraAlpine tundra
30Arctic tundraPermafrost: a layer of frozen ground, found under the thin layer of top soil, which never thaws.The soil in the tundra is lacking in nutrients because low temperatures slow the decay process.Short growing season.Long days during the “summer” and long nights during the “winter”.Mosquitoes are the most common tundra animal.
31Alpine TundraThe alpine tundra biome exists on rocky mountaintops. Because trees cannot grow at this high altitude, most of the alpine tundra plant life consists of shrubbery and small leafy plantsAnimals include bighorn sheep, mountain goats, elk, pika, marmots, and birds such as the white-tailed parmigan and the grouse.
34Taiga (northern coniferous forest) Lies just south of the tundra.Still harsh but although often are warmer and wetter than the tundra.Permafrost is usually absentConifer needles make the soil acidic and poor in minerals.More large species (moose, deer, lynx, wolves)
38PrairiesLarge communities covered with grasses and similar small plants.Climate where dry seasons occur so cannot support forests.Rich soil due to yearly die-off of grasses.Animals include large herbivores such as deer and bison. Predators include the wolf, coyote, and fox. Small animals like the rabbit, praire dog, and chipmunk (pocket gopher).
40SteppeThe Steppe biome is a dry, cold, grassland that is found in all of the continents except Australia and Antarctica. It is mostly found in the USA, Mongolia, Siberia, Tibet and China.
41Steppe cont.The Steppe biome is usually found between deserts and forests. If it got more rain, it would become a forest. If it got less rain, it would become a desert. The average rainfall is inches per year, with 4-5 being received in the spring.
42SavannaA savanna is a rolling grassland scattered with shrubs and isolated trees, which can be found between a tropical rainforest and desert biome. Not enough rain falls on a savanna to support forests. Savannas are also known as tropical grasslands. They are found in a wide band on either side of the equator on the edges of tropical rainforests.
45Forest BiomesRepresent the largest and most ecologically complex systems. They contain a wide assortment of trees, plants, mammals, reptiles, amphibians, invertebrates, insects and micro-organisms which vary depending on the zone's climates.
462 Types of temperate forests Deciduous forestsRain forests
47Temperate Deciduous Forest Are a close relative of the Taiga biome, and can be found in areas with a milder, shorter winter season.Trees in the temperate forest include evergreens, maple, elm, oak, cedar and other trees which shed their leaves in the fall. The temperate forest's soil in richer than that of the coniferous forestsThe forests' canopy is thinner, allowing more light and heat to penetrate, permitting photosynthesis in the forest floor plantsAnimals include cold blooded such as garter snakes, turtles, and a few amphibians as well as a variety of warm blooded animals.Many species hibernate, and/or burrow in the ground to pass the winter months.
50Temperate Rain ForestBorders oceans and found on western edge of North and South Americamoist air from the Pacific Ocean drops between 60 and 200 inches of rain a year
51Temperate Rain Forest cont. The temperate rain forest has seasonal variation, with summer temperatures rising to about 80 ˚F and winter temperatures dropping to near freezing. In the northernmost regions, winter may be cold enough for some ice and snow.Although this rain forest has layers of tall, medium, and low growing vegetation, the cool winters limit the numbers and kinds of life forms that live here. Compared to the tropical rain forest, the temperate rain forest has a less complex ecology.
52Tropical Rain Forest Found along the equator Receives as much as 400 cm of rain a year with an average temp. of 25˚CAs a climax comm. The forest floor is bare due to thick canopy.Thick canopy full of diverse life.