Earth: A Living planet

 To properly care for our planet, we must understand how the living world operates.

 We study ecology, or the study of the interactions of organisms with one another and with their physical surroundings.

 The part of the planet in which life exists is called the biosphere.

Where do we find life?

 The part of the planet in which life exists is called the biosphere.

 It includes all the areas of land, air and water on the planet as well as all the life that populates these areas.

 Biosphere extends from about 8 km above the earth’s surface to as far as 8 km below the surface of the ocean.

 Living organisms are not evenly distributed throughout the biosphere-why not?

Ecosystems

 The biosphere is too large to study so scientists break it down into small units called ecosystems.

 Ecosystems include a given area’s physical features (abiotic factors) and living organisms (biotic features)  What are the abiotic and biotic factors in a pond ecosystem?

Pond ecosystem

 Abiotic factors  Water  Sunlight  Soil type  Rocks  Temperature  Humidity  Elevation  rainfall  Biotic factors  Fishes  Frogs  Insects  Snails  Worms  Amoebas  Water lilies

Community

 The organisms living together in an ecosystem  Ex- a forest community would include trees, bird and fungi  Ecosystems are not self-contained-they don’t function independently of one another.

Ecological succession

  Ecosystems change with time because every organism effects environmental conditions around it.

 ex- Burrowing worms change the texture of soil.

 Trees shade the area beneath their branches, making it cooler Because of this, many ecosystems undergo ecological succession- a process in which an existing community of organisms is replaced by a different community over periods of time ranging from a few decades to thousands of years.

 Sometimes succession occurs in places where no living community existed before.

 Ex- new volcanic islands  Organisms that colonize such areas are called pioneer species.

 Lichen are typical pioneer species  Changes in species, physical factors, natural disasters, human intervention are all things that can cause succession.

 Succession often leads to a fairly stable collection of organisms called a climax community.

 These are often described by the predominent species they contain  Ex- temperate zone beech-maple forest

Biomes

 A broad area of earth’s surface characterized by distinctive vegetation and associated animal life; for example. Broad-leaf forest biome, grassland biome, desert biome.

Land Biomes

 Tundra  Northernmost land biome  Nearly treeless but with mosses, lichens, grasses  Animals migrate there during the summer – caribou, reindeer, wolves, foxes, hordes of mosquitoes  Characteristics  permafrost- layer of permanently frozen subsoil; only a few centimeters thaw before its frozen again; this keeps plants small and stunted.

Taiga (Boreal Forest)

 From Russian word meaning primeval forest  Much of N. America/Asia- coast of N. California, Washington, Oregon –home of giant redwoods (tallest trees in the world – 60 meters)  Cold summers that are mild enough and long enough to allow plants and animals to reproduce  Many animals, birds

Temperate Deciduous Forests

 Eastern US, most of Europe, parts of Japan, china and Australia  Changing seasons and leaf fall  Many animals- a lot hunted to extinction-deer, moose, gray foxes beginning to reappear  An abundance of organic matter and nutrients stored in a layer called humus, making this good farmland  Human activity (clearing) in New England, but much has been recovered

Grasslands

 Many interior parts of continents  Vast areas covered with grasses and small leafy plants  Significant rainfall that falls during one season  Plains and prairies of N. America, steppes of Soviet Union, veld of S. Africa and pampas of Argentina  Midwest US- hot summers, cold winters  Tropical grasslands- little seasonal temperature change seasons change from wet to very dry- called savannas  Animal grazing keeps succession down  Overfarming causes wind erosion

Tropical Rain Forest

 Warm temperatures (25 C) and year round rainfall (200 400 cm)  Large areas of S. America, SE Asia, Africa, Central America  Home to more species of plants and animals than the rest of the land combined  70 meter tree canopy; lianas (wrapping vines)  Animal life rich and varied. Many are tree dwellers-forest floor holds danger  Chemicals found for diseases; destruction may be imminent

Deserts

 Less than 25 cm of rainfall a year  Sahara- Africa- largest desert- desolate, virtually no plant life  Can be seasonal deserts- some rainfall- home to rapidly growing plants with extensive surface roots-SW US and Mexico  Mountainous deserts- higher altitude-called cold deserts- brief rainy season- some grasses and shrubs  Irrigation can make suitable for farming- often very fertile soil- working on it

Aquatic Biomes

 Freshwater biomes  Rivers, streams, lakes  Provide much of our drinking water  Important source of food  Large rivers (Nile-Africa, Amazon-S. America) home to many species of insects, fish, amphibians,reptiles and mammals  Human dumping grounds for waste

Marine Biomes

 Vast habitats or the ocean  Photic zone- the short distance that can be penetrated by sunlight- where photosynthesis takes place in plants  May be as shallow as 30 m in N. Atlantic or as deep as 200 m in S. Pacific Ocean  Layer where phytoplankton (tiny free-floating photosynthetic organisms) and algae grow  Oceanographers have divided the ocean into ecologically distinct zones depending on depth and distance from shore.

Intertidal Zone

 Most difficult for organisms to live in  Part of the day underwater; part of the day exposed to air and sunlight; pounding surf; surging waves  Some organisms burrow (clams);some attach themselves to rocks (barnacles, seaweed) still others cling by their feet or suckers (snails, sea urchins, starfish)

Neritic Zone

 The part of a marine biome that extends from the low tide line to the edge of the open ocean  Larger algae (seaweed) are abundant because its in the photic zone  Huge numbers of marine life reside here/hunt here  Fish, invertebrates, turtles, lobsters, crabs, flounder, rays

Open-sea zone

 Phytoplankton responsible for 80-90% of earth’s photosynthesis  Food chains are at work  Fish, mammals, sea birds reside here  More phytoplankton closer to shore (more nutrients), hence more fish closer to shore  Unfortunately makes them more susceptible to human pollution and over-fishing

Deep-Sea Zones

 Area of high pressure, cold temperatures and total darkness  Until recently thought to be devoid of life  Home to some of the strangest creatures- gulper eels with mouths that make up ½ of their body; giant squid with glowing side spots; huge sea cucumbers lumber on the bottom  Zooplankton (free-floating microscopic animals) hide out here during the day and come to the top at night

Estuaries

 Found at the boundary between fresh water and sea water  Salt marshes, mangrove swamps, lagoons, and river deltas  Relatively shallow, high photosynthetic areas  Sheltered area for fish laying and bird nesting

Energy and Nutrients: Building the Web of Life  One of the most important factors in an ecosystem is the flow of energy.  Only 0.1% of the sun’s energy that reaches the surface is used by living things  1/2 of the energy absorbed by plants is used immediately- the rest is stored in plant tissue in compounds called carbohydrates

 Animals that eat plants obtain this energy.

 They use much of it and store very little in tissues.

 Energy cannot be recycled or used again so they don’t call it an energy cycle but rather an energy flow.

Energy Flow- 1

st

step

 Sunlight (solar energy) trapped by plants (and some bacteria) and changed into carbohydrates through photosynthesis.

 Producers – photosynthetic organisms capable of making their own food.

Energy Flow – 2

nd

step

   Directly – eat plants- primary consumers- herbivores  Animals are consumers. They get their energy either directly or indirectly from producers Indirectly- eat animals that eat plants – secondary, tertiary or quaternary consumers-carnivores

Energy flow- 3

rd

step

 When producers and consumers die, their remains do not build up because of

decomposers

   Decomposers obtain their energy from non-living organic matter They break down dead material Include fungi and bacteria

Summary – energy flow

 Each step is called a trophic level  At each trophic level, energy is used and less is available to the next level  As a rule, only about 10% of the energy at one level is stored to be used by the organisms at the next level.

 Scientist use an ecological pyramid to represent the energy relationships among trophic levels.

Biogeochemical Cycles

 Although energy moves in a one-way direction through an ecosystem, nutrients are recycled.

 They are called biogeochemical cycles because nutrients, unlike energy may be used over and over again by living systems.

Water cycle

 The movement of water from the atmosphere to the earth and back to the atmosphere

Nitrogen cycle

 All organisms require nitrogen to build proteins  Although 78% of the air is nitrogen gas, most organisms can’t use it in this form.

 The nitrogen cycle shows the movement of nitrogen through the biosphere

Carbon and Oxygen cycles

Nutrient limitations

 The rate at which producers can capture energy and use it to produce living tissue is controlled by several factors, one of which is the amount of available nutrients.

 If the nutrients are in short supply, it is called a limiting factor  Ex- adding large amounts of nitrogen to coastal water causes tremendous growth, or an algal bloom.

 Adding a bit of fertilizer doesn’t usually harm an ecosystem, but adding too much can cause harm.

Feeding relationships

  Simplest – food chain Usually more complex- food web

Can find more info in Ch. 17 & 18.

 End of material for second test

Populations

 A group of organisms that all belong to the same species and that live in a given area

Exponential Growth

 Almost any organism provided with ideal conditions for growth and reproduction will experience a rapid increase in its population  The larger the population gets, the faster it expands  It produces a growth curve called an exponential growth curve  Left unchecked, one bacteria could exponentially reproduce to cover the planet three miles thick in 72 hours.

 One pair of elephants could produce in 19 million offspring in 750 years!

Logistic Growth: closer to reality

 Most populations go through a number of growth phases which can be represented on a logistic growth curve.

A B C D E A- at first their numbers increase slowly B- the population soon grows rapidly (exponentially) C- speed of the growth begins to slow down- the population grows but not at as quick a rate D- from here on it grows more and more slowly until E- population growth becomes steady-the

steady state-

the birth rate is roughly equal to the death rate- population is maintained

Steady state line represents the carrying capacity of a particular environment for a particular species- certain factors keep the population from growing further.

Factors that control population growth

 Density-dependent limiting factors- usually operate only when populations are large and crowded  Competition  Predation  Parasitism  Crowding and Stress

Competition- plants and animals compete for food, water, space, sunlight and other essential of life  Competition between members of different yet similar species is a major force behind evolutionary change  No two species occupy the same niche in the same place at the same time  When two species compete, both find themselves under pressure from natural selection to change in ways that decrease their competition.  This is important because it ties ecology to evolution  It is an example of how all biological sciences are interrelated when you look at them from an evolutionary point of view

Predation

 Predator prey relationships exist for just about every species  As prey numbers increase, its easier to get. More get eaten and their numbers decrease.

 As predator numbers increase, the food source gets used up and their numbers decrease.

 Important to maintain both groups  Ex .   wolves, bobcats and deer Rabbits in Australia