Chapter 6 Notes
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Date Created: 10/04/15
32110 Notes Chapter 6 Ecology Preserving the Animal Kingdom Ecology is the study of the relationships of organisms to their environment and to other organisms Studying ecology is the key to not only understanding why animals behave how they do why they live where they live why they eat certain foods why they interact with specific animals etc but also how human activities can harm animal populations Section 61 Animals and Their Abiotic Environment An animal s habitat includes all living biotic and nonliving abiotic characteristics of the area in which the animal lives Abiotic characteristics include but are not limited to temperature oxygen availability and light Animals live within a certain range of abiotic characteristics that are known as the tolerance range The range of values within the tolerance range where an animal is the most successful is known as the range of optimum When a certain factor is out of an animal s tolerance range it becomes a limiting factor and could prevent the animal from reproducing or surviving An animal s response to an abiotic factor is often to orient itself with respect to that factor which is known as taxis For instance if an animal prefers to live in an environment with a lot of light it will move towards a light source known as positive phototaxis ENERGY Energy is the ability to do work Work involves a variety of things from looking for food to moving cells around inside the animal s body Heterotrophic animals rely on ingesting other organisms to make energy while autotrophic animals get their energy from photosynthesis or other carbonfixing activities An account of an animal s energy intake and how it spends that energy is known as an energy budget The total energy that an animal intakes is the gross energy intake Some of this energy is lost to excretory energy excretion and existence energy minimal maintenance activities such as pumping blood exchanging gases etc and any energy left after those processes goes towards productive energy growth mating nesting caring for young etc Survival requires that animals get enough 1Page 32110 Notes energy to supply these functions Favorable energy budgets are difficult to obtain especially during winter TEMPERATURE A portion of an animal s existence energy is spent to regulate body temperature Body temperature is rarely constant because of the inequality between heat loss and heat gain When food becomes scarce an animal s metabolic activities decreases dramatically Torpor is a time of decreased metabolism and lowered body temperature that allows animals to survive brief periods of time when they do not feed this often happens in birds and bats that need to feed almost constantly when they are active Hibernation is a time of decreased metabolism and lowered body temperature that may last for weeks or months this usually occurs in small mammals such as rodents shrews and bats Winter sleep is similar to hibernation but occurs mostly with larger animals and the animal is able to wake up and become active very quickly Aestivation is a period of inactivity in some animals that must withstand extended periods of drying often by creating burrows and only emerging after moisture returns Torpor winter sleep hibernation and aestivation are all forms of controlled hypothermia and are different forms of the same physiological processed They differ by the extent to which the body temperature falls the duration of the state and the season in which they occur OTHER ABIOTIC FACTORS Other abiotic factors include moisture light geology and soils Life s processes occur in the watery environment of the cell The water that is lost must be replaced Light is used for reproduction and migration The soil can hinder the animals living in or on it as well as the plants that grow out of it Section 62 Biotic Factors Populations Biotic characteristics of a habitat include interactions that occur when an individual s own species as well as other species Examples of biotic factors are population growth how growth is regulated food availability and competition for food etc ZIPage 32110 Notes POPULATION GROWTH A population size changes as a result of birth death and dispersal A way to characterize a population is how well the chances of survival of an individual change with age this is known as survivorship There are three different ways to characterize a population this way 1 Individuals in Type 1 populations survive to an old age and then die rapidly Environmental factors do not really influence the life span of individuals Humans are an example of this 2 Individuals in Type 2 populations have a constant probability of death throughout their lives The environment has an important influence on death although it is no harsher on the young than it is the old Some rodent populations are an example of this 3 Individuals in Type 3 populations experience very high juvenile mortality but once they reach adulthood the mortality rate decreases significantly Most fish populations are an example of this A second attribute of populations is how fast a population grows Populations experience exponential growth Not all populations display the same capacity for growth Factors that could affect growth are the number of offspring produced the likelihood of survival to reproductive age the duration of reproductive period and the length of time it takes to reach maturity Exponential growth cannot occur forever There is a point where the amount of resources will not be able to sustain the population The environmental constraints that are put on population growth is known as environmental resistance The population size that the environment can support is the environment s carrying capacity A population growth is therefore referred to as a logistic population growth POPULATION REGULATION The conditions that an animal must meet to survive is different for every species But every species has a population density and competition that affects populations in predicable ways Densityindependent factors influence the number of animals in a population without regard to the density of the population individuals per unit space Weather conditions are an example of this An extremely cold winter with little snow cover could devastate a population of lizards Regardless of the size of the population a certain percentage of individuals will freeze to death Densitydependent factors are more severe when the population density is high or sometimes very low than they are at other densities Competition for resources disease predation and parasitism are examples of densitydependent factors BIPage 32110 Notes INTRASPECIFIC COMPETITION Competition occurs when animals utilize similar resources and in some way interfere with each other s procurement of those resources Competition among members of the same species intraspecific competition is often intense because the resource requirements of individuals are nearly identical This can occur without the individuals coming in direct contact such as the saying quotthe early bird gets the worm The later birds won t have any worms to eat Section 63 Biotic Factors nterspecific Interactions Members of other species affect all characteristics of a population nterspecific interactions include herbivory predation competition coevolution and symbiosis The nature of interspecific interactions may change as an animal matures or as seasons or the environment change HERBIVORY AND PREDATION Herbivores are animals that feed on plants by cropping portions of the plant but not usually killing the plant If the animal killed the plant while they were eating it then they would run out of food very quickly Predators feed by killing and eating other organisms INTERSPECIFIC COMPETITION When members of different species compete for resources one species may be forced to move or become extinct or the two species may share the resource and coexist Most species in completion will learn to coexist Coexistence can occur when species utilize resources in slightly different ways Robert MacArthur studied five species of warblers that all used the same caterpillar prey Warbles partitioned their spruce tree habitats by diving the tree into preferred regions for foraging COEVOLUTION Coevolution is the evolution of ecologically related species is sometimes coordinated such that each species exerts a strong selective influence on the other This can occur either when species are competing for the same resource or in predatorprey situations In predatorprey situations natural 4Page 32110 Notes selection helps the prey become more elusive to avoid being hunted The predator counters this with natural selection passing down traits that helps them catch and immobilize prey An example of this type of coevolution is the lynx and the snow hare SYMBIOSIS Symbiosis is when two different species live together in continuing intimate associations These interactions influence the species involved in different ways There are three different type of symbiosis 1 Parasitism is where an organism known as the parasite lives in or on a second organism known as the host The host usually survives at least long enough for the parasite to complete at least one life cycle There are different types of host The first is the intermediate host which only serves as a host in order for the parasite get to the host it actually wants which is referred to as the definitive host Tapeworms are an example of parasitism They use cows and pigs as an intermediate host to get to humans which is the definitive host 2 Commensalism is a relationship where one member befits while the other is neither harmed nor helped 3 Mutualism is a relationship in which both members benefit An example of this is clown fish and the sea anemone The clown fish gets protection while the sea anemone gets cleaned and gets extra nutrients OTHER INTERSPECIFIC ADAPTIONS nterspecific interactions have created other characteristics of animals Camouflage occurs when an animal s color patterns help hide the animal from predators Cryptic coloration is a type of camouflage where an animal s color pattern matches the environment to prevent the animal being seen Countershading is a type of camouflage where the top of the animal is shaded differently from the bottom A shark is an example of this dark colors on the top to prevent predators looking down through the water and seeing them light colors on the bottom to prevent prey from seeing them when they look up Other animals protect themselves by having brightly colored patterns to warn predators that they are dangerous This is known as aposematic coloration Some species will resemble one another to gain an advantage which is known as mimicry Some species of butterfly do this because it makes the birds think they are not tasty SIPage 32110 Notes Section 64 Communities All populations living in a specific area make up a community Communities have a unique organization such as some communities having certain members that have importance in determining community characteristics For instance in a stream species there might be a lot of trout which reducing the competition among prey species The trout in this case would be known as the keynote species Community species diversity is the variety of animals in a community Some factors that promote a high diversity are climate stability moderate levels of predation high productivity and a wide variety of resources THE ECOLOGICAL NICHE A niche of any species includes all of the attributes of an animal s lifestyle what it eats where it eats where it nests etc Competition results when two niches overlap COMMUNITY STABILITY Communities are born and they die and between those two times is constant change Some changes are caused by the climate while others are caused by members of the community The dominate members change the community in predictable ways in a process that is called succession The first community to be established in a location is called the pioneer community Each successional state is called a seral stage and the entire successional sequence is a sere The final community is called the climax community Section 65 Trophic Structure of Ecosystems Communities and there physical environments are called ecosystems Energy is constantly being used and once it leaves the ecosystem it is never reused Energy is usually introduced into the ecosystem in the form of sunlight that is incorporated into chemical bonds of organic compounds The total amount of energy converted into organic compounds in a given are per unit time is called primary GIPage 32110 Notes production The total mass of all organisms in an ecosystem is the biomass Energy is eventually lost as heat The sequence in which energy moves through the ecosystem is known as the food chain and interconnected food chains are known as food webs Organisms are sometimes grouped according to the form of energy used and these groups are known as trophic levels Producers obtain nutrition from inorganic materials and they make up the first trophic level Other levels are made up of consumers obtain energy through eating other organisms Decomposers break down dead organisms by digesting organisms SECTION 66 CYCLING WITHIN ECOSYSTEMS Matter is constantly cycled in ecosystems through the biogeochemical cycles Nearly all of living matter is made up of oxygen carbon nitrogen and hydrogen Matter is incorporated into living tissue passed between organisms and eventually returned to the energy reservoir Matter is never lost and when it is used it will eventually be used again Section 67 Ecological Problems HUMAN POPULATION GROWTH Nearly all of the environmental problems comes from the growing human population The earth has a carrying capacity and it is hard to determine where that point is However if the growing human population is not capped the earth will suffer for it With medicine improving and the infant mortality rate dropping in developing countries the population is exploding The earth s population is expected to reach about 10 billion by 2100 EARTH s RESOURCES TOO BIG OR LET FAIL The variety of living organisms in an ecosystem is called biodiversity No one knows how many species there are in the world Scientists estimate that there are over 30 million Every species does its part to keep the earth safe and clean However expanding human populations are destroying habitats which destroys the ecosystem In addition pollution is a big concern because it disrupts the nature of the species living anywhere near humans which is basically every species Humans have to deal with 7Page 32110 Notes problems such nitrogen cycling phosphorus cycling climate change land use ocean acidification fresh water and ozone depletion BIPage
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