Edited Invalid date
Chapter 139 -- Part 2: Properties of Populations
The food chain is where food is moved from one level to another.
Most of the energy stored in trophic levels is converted to organic matter at the next trophic level.
The food chain can support only 10 kJ of tertiary consumers if you start with 10,000 kJ of plant matter.
Food chains are short because of the loss of energy from one level to the next.
They don't have more than four or five levels.
Long food chains are less stable than short ones.
Local extinction of top predator is caused by population fluctuations at lower levels.
A good model to demonstrate the interaction of organisms in the food chain is the food pyramid.
Food chains are interwoven with other food chains into a food web.
An animal can occupy different levels in a food chain.
Humans can be primary consumers when eating vegetables, but tertiary consumers when eating a steak.
There are two components to species diversity, the variety of kinds of organisms that make up a community.
There is a number of different species in the community.
The proportion of different species within a community is called relative abundance.
Communities that have a lot of diversity are better able to fight off invaders.
They are able to recover from environmental stresses.
One unfortunate example of the importance of diversity in a community is here.
Communities are made up of populations of organisms.
The Cavendish is the only banana variety cultivated in the world.
The Cavendish is being attacked by a fungus.
It has destroyed crops in Taiwan, Indonesia, and Malaysia and threatens plantations in South and Central America.
The lack of diversity in banana culture has left the banana vulnerable to disease and may leave us with no bananas to eat.
In a community, the species that are most abundant are the ones that have the highest amount of biomass.
They control the distribution of other species.
There are sugar maples in North American forests.
They affect the abiotic factors, such as shade and soil nutrients, which in turn provide special habitats for many other species.
There are not many keystone species in the community.
They control other species in the community.
There are sea otter in the North Pacific.
They are high in the food chain and feed on sea urchins.
There aren't many sea otter and there aren't many sea urchins and kelp forests.
In contrast, where orcas feed on sea otter, sea urchins and kelp are rare.
There are two models for the structure of a community.
Influence from lower to higher trophic levels is the focus of the bottom-up model.
Increasing the availability of minerals in the environment will increase the amount of wood produced by the producers, and will increase the amount of wood used by the trophic level.
The effect will not extend down to the bottom levels if you add or remove predators.
The top-down model was developed in 1963.
An increase in the mass of producers can be achieved by removing the top carnivores from a community.
The model is called the trophic cascade.
An excellent example is what happened in the park.
The wolves were reintroduced in the park in the 1990s after public sentiment shifted.
When there were no wolves, the aspen tree population in the park decreased from 6 to 1%.
The density of the aspen trees increased when wolves were reintroduced into the park.
It is thought that the pressure on the elk population was caused by the wolf population.
Organisms at higher levels have more toxins in their bodies than those at lower levels.
The phenomenon is called biological magnification.
The bald eagle almost became extinct because Americans sprayed the pesticide DDT in the 1950s, which entered the food chain and accumulated in the bald eagle at the top of the food chain.
Few eaglets hatched because the thin-shelled eggs were broken easily.
The bald eagle was saved from extinction because of human intervention.
Decomposers are usually not depicted in a food chain diagram.
Without decomposers, there would be no food chain and no life.
Most communities are not stable.
The carrying capacity is affected by the size of the population.
The entire food chain can be altered by the migration of a new species.
Disasters like volcanic eruptions, strip mining, clear-cutting a forest, and forest fires can destroy a community.
The process of sequential rebuilding is called ecological succession.
In a lifeless area where soil has been removed, the process of rebuilding is called primary ecological succession.
The main characteristic of primary succession is soil building.
The first organisms to colonize a barren area are mosses and lichens, which are introduced into the area by the wind.
The organic matter accumulates from the remains of the pioneer organisms.
Grasses, bushes, and then trees overrun pioneer organisms once soil is present.
The climax community is the final stable community.
A disaster that destroys the system again is called a blow up.
The southern edge of Lake Michigan was studied in detail.
After the last ice age, the lakeshore left a series of new beaches and sand dunes.
A person who begins at the water's edge and walks south for several miles will pass through a series of communities that were formed in the last 10,000 years.
The various stages begin with bare, sandy beach and end with a community of old, well-established forests.
In some cases, the climax community is a beech-sugar maple forest; in other areas it is a mix of oak and hickory.
Secondary succession occurs when an existing community is cleared and the soil remains intact.
In 1988 fires destroyed all the old growth that was dominated by lodgepole pine, but left the soil intact.
New vegetation was covered by the burned areas within a year.
It is unlikely that the AP exam will test you on biomes, but they are important biological phenomena that you should be familiar with.
The distribution of the earth's Biomes depends on the amount of precipitation and temperature in the area.
The dominant vegetation and animal life of each biome.
There are many different types of flora and fauna.
If you travel north from the equator, you will pass through the tropical rainforest, desert, temperate grassland, taiga, and tundra.
Similar to changes in latitude, changes in altitude produce effects.
On the slopes of the Appalachian Mountains in the east and the Rockies and coastal ranges in the west, there is a similar trend.
As elevation increases and temperatures and humidity decrease, one passes through deciduous forests to taigas.
There is an overview of the world's major biomes.
Tropical rainforests are found near the equator with abundant rain, stable temperatures, and high humidity.
The forests cover only 4% of Earth's land surface, but they account for 20% of Earth's net carbon fixation.
Tropical rainforests have a lot of different species.
They may have as many as 50 times the number of trees as a forest.
The floor of the forest is dimly lit at midday because of the dense canopy of the dominant trees.
The canopy keeps rain from falling directly onto the forest floor.
Epiphytes are plants that grow on other trees rather than supporting themselves.
They are not parasites and may kill the trees by blocking the light.
The most diverse animal species in the world are found in tropical rainforests.
Many species are in danger.
Deserts have less than 25 cm of rain per year.
Deserts have the most extreme temperature fluctuations.
The daytime surface temperature can be as high as 70degC.
The heat is lost quickly at night.
After sundown, temperatures plummet.
The characteristic of the desert is that cacti with shallow roots can capture as much rain as possible during hard and short rains.
Other plants include sagebrush and creosote bush.
There are many small annual plants that grow after a hard rain and die within a few weeks.
When the heat is not so intense, most animals are active at night or early morning.
They remain cool during the day by hiding in the shade or burrowing underground.
The cacti can expand to hold more water and have leaves that protect it from animals attacking it for its water.
There are regions hundreds of miles across in the Sahara Desert that are completely barren of vegetation.
Rodents, kangaroo rats, snakes, lizards, arachnids, insects, and a few birds are characteristic animals.
There are huge areas in both the tropics and the tropics.
The conditions for forests are inhospitable because of low total annual rainfall.
The United States and Africa have bison and pronghorn antelope.
Prairie dogs and other rodents are common.
In the northeast of North America, south of the taiga, there are forests characterized by trees that drop their leaves in winter.
There are more plant species in the taiga.
There are species of plants and animals that live on the ground, on the low branches, and on the treetops.
The soil is rich because of leaf litter.
Squirrels, deer, fox, and bears are the principal mammals.
Much of the world's northern regions are located in northern Canada.
They are dominated by conifer forests.
There are lakes, ponds, and bogs in the landscape.
They have very cold winters.
This is the largest area.
Taigas are characterized by heavy snowfall and the trees are shaped with branches directed downward to prevent snow from breaking their branches.
Black bears, moose, and other large mammals are the principal large mammals.
In the summer, flying insects and birds are abundant.
Taigas have more variety in animals than tundras do.
The far northern parts of North America, Europe, and Asia are home to the Tundras.
They are characterized by frozen subsoil found in the farthest point north.
The frozen desert is often referred to as the frozen desert because it gets very little precipitation.
There are many lakes, ponds, and bogs in the tundra.
There are many insects, particularly flies.
The principal mammals are reindeer, caribou,Arctic wolves,Arctic hares, lemmings, and polar bears.
The number of organisms in the tundra is large, but the number of species is small.
A subset of the high Arctic tundra is a strong carbon sink.
The activities of organisms can be affected bybiotic and abiotic factors.
View flashcards and assignments made for the note
Getting your flashcards
Privacy & Terms