For all=EIS=9 GraderS*08-09

ลำดับตอนที่ #8 : [[R.S.]]Biology Test::Chapter 5-6.3+6.4::27.10.08

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The Summary of Biology for

Chapter 5 :: Populations &

Chapter 6 :: Humans in the Biosphere

Chapter.5 :: Populations  [[Page.118]]

5-1 How Populations Grow [[Page.119]]

-          Important characteristics of a population are …

1.      Geographic distribution [[or range]]

= the area inhabited by a population

2.       Population density

= the number of individuals per unit area

3.       Growth rate

= three factors that can affect population size are …

1)      the number of births [[birthrate]]

2)      the number of deaths [[death rate]]

·         birthrate > death rate = population increase

·         birthrate < death rate = population decrease

·         birthrate = death rate = stay more or less than the same size

3)       the number of individuals that enter or leave the population

3.1  Immigration = the movement of individuals into an area

[[increases population size]]

3.2  Emigration = the movement of individuals out of an area

[[decreases population size]]

4.       Population’s age structure

-          If a population has abundant space and food, and is protected from predators and disease, then organisms in that population will multiply and the population size will increase. This produces the graph with J-shaped curve and indicates exponential growth.

·         Exponential growth occurs when the individuals in a population reproduce at a constant rate.

·         Under ideal conditions with unlimited resources, a population will grow exponentially.

·         But it can’t continue in natural populations for very long.

-          As resources through less available, the growth of a population slows or stops. This produces the graph with S-shaped curve and indicates logistic growth.

·         Logistic growth occurs when a population’s growth slows or stops following a period of exponential growth.

ð  Even when the population growth is said to stop, it’s still rising & falling somewhat, but the ups & downs average out around a certain population size.

·         In logistic growth graph, the largest number of individuals of a population that a given environment can support is called carrying capacity.

PIX OF LOGISTIC GROWTH GRAPH [[download la ja hen ^^]]

5-2 Limits to Growth [[Page.124]]

-          A limiting factor is a factor that causes population growth to decrease.

[[ex. limiting nutrient]]

1.      Density-dependent limiting factor

= it depends on population size and is become limiting only when the population density reaches a certain level.

= it includes …

·            Competition

ð  When populations become crowded, organisms compete with one another for food, water, space, sunlight, and other essentials.

ð  When two species compete for the same resources, both are under pressure to change in ways that decrease their competition becuz no two species can occupy the same niche in the same place at the same time.

·            Predation

ð  The regulation of a population by predation takes place within a predator-prey relationship.

·            Parasitism and disease

ð  Like predators, parasites take nourishment at the expense of their hosts, often weakening them and causing disease or death.

2.      Density-independent limiting factor

= it affects all population in similar way, regardless of the population size.

= Ex. unusual weather, natural disasters, seasonal cycles, and certain human activities – such as damming rivers & clear-cutting forests

= populations often grow and shrink in response to such changes

5-3 Human Population Growth [[Page.129]]

-          Like the population of many other living organisms, the size of the human population tends to increase with time.

-          The human population cannot keep growing exponentially forever, because Earth and its resources are limited.

-          The scientific study of human populations is called demography.

·         It examines the characteristics of human populations and attempts to explain how those populations will change over time.

-          Birthrates, death rates, and the age structure of a population help predict why some countries have high growth rates while other countries grow more slowly.

-          According to the demographers’ hypothesis, U.S., Japan, and much of Europe have completed the demographic transition, a dramatic change in birth and death rates.

·         Before, human societies have had high death rates & birthrates, but with advances in nutrition sanitation, and medicine, more children survive to adulthood & more live to old age. These changes lower death rate and begin the demographic transition.

·         The demographic transition is complete when the birthrate falls to meet the death rate, and the population growth stops.

[[PIX OF DEMOGRAPHIC TRANSITION GRAPH ,, download la ja hennn]]

=don’t mind with da 4^th stage and green line thingy ..

in da book it has only 3 stages but I’m too lazii to cut it out=

-          Population growth depends, in part, on how many people of different ages make up a given population.

-          Demographers can predict future growth using models called age-structure diagrams, or population profiles.

·         It shows the population of a country broken down by gender and age group.

-          To predict the world’s human population will grow, demographers must consider many factors including the age structure of each country and the prevalence of life-threatening diseases, such as AIDs.

Chapter.6 :: Humans in the Biosphere  [[Page.138]]

6-3 Biodiversity [[Page.150]]

-          Human’s well-being is closely tied to the well-being of a great variety of other organisms. [[another word for variety is diversity]]

-          Biological diversity, or biodiversity, is the sum total of the genetically based variety of all organisms in the biosphere.

1.      Ecosystem diversity = includes the variety of habitats, communities, and ecological processes in the living world.

2.      Species diversity = refers to the number of different species in the biosphere.

3.      Genetic diversity = refers to the sum total of all the different forms of genetic information carried by all organisms living on Earth today.

-          Biodiversity is one of Earth’s greatest natural resources. Species of many kinds have provided us with foods, industrial products, and medicines – including painkillers, antibiotics, heart drugs, antidepressants, and anticancer drugs.

-          Human activities can reduce biodiversity by altering habitats, hunting species to extinction, introducing toxic compounds into food webs, and introducing foreign species to new environment.

·         Extinction occurs when a species disappear from all or part of its range & it can be lead from human activities.

·         A species whose population size is declining in a way that places it in danger of extinction is called an endangered species.  

-          When land is developed, natural habitat, which supply organism needs, may be destroyed. As habitats disappear, the species that live in those habitats vanish.

·         In addition, development often splits ecosystems into pieces, a process called habitat fragmentation.

·         As a result, remaining pieces of habitat become biological islands. The smaller the island, the fewer species can live there + the smaller their populations can be.

-          Throughout history, human have pushed some animal species to extinction by hunting them for food or other products.

-          Many forms of pollution can threaten biodiversity, but one of the most serious problems occurs when toxic compounds accumulate in the tissues of organisms.

·         Ex. DDT, widely used pesticides which remains active for a long time, kills many different insects, and can control agricultural poets & disease-carrying mosquitoes.

ð  DDT is nonbiodegradable [[can’t broken down by metabolic processes in bacteria, plants, or animals]] and when it’s picked up by organisms, they don’t eliminate it from their bodies.

·         In the process called biological magnification, concentrations of a harmful substance increase in organisms at higher trophic level in a food chain or food web, although top-level carnivores are at highest risk.

ð  Ex. when plants pick up DDT from water, DDT is stored in its tissue. When herbivores eat those plants, they too store DDT & as they eat more plants, the DDT becomes concentrated very much higher. Then, when carnivores eat herbivores, DDT is concentrated further.

-          One of the most important threats to biodiversity today comes from an unexpected source :: apparently plants & animals that humans transport around the world either accidently or intentionally.

·         Introduced into new habitats, these organisms often become invasive species that reproduce rapidly.

ð  They increase their population becuz their new habitat lacks the parasites and predators that control their population ‘back home’

-          Conservation is the wise management of natural resources, including the preservation of habitats and wildlife. [[to protect biodiversity]]

·         Today, conservation efforts focus on protecting entire ecosystems as well as single species. Protecting an ecosystem will ensure that the natural habitats & the interactions of many different species are preserved at the same time.

·         As part of the effort to locate problem areas and set up a list of priorities, conservation biologists identify biodiversity ‘hot spot’.

ð  Each hot spot is a place where significant numbers of habitats & species are in immediate danger of extinction as a result of human activity.

·         Protecting resources for the future can require people to change the way they earn their living today. But if we don’t take some difficult steps today, some resources may disappear.

6-4 Charting a Course for the Future [[Page.157]]

-          Researchers are gathering data to monitor and evaluate the effects of human activities on important systems in the biosphere. Two of these systems are the ozone layer high in the atmosphere and the global climate system.

-          Between 20 and 50 kilometers above Earth’s surface, the atmosphere contains a relatively high concentration of ozone gas called the ozone layer.

·         Molecules of ozone consist of three oxygen atoms

·         Ozone absorbs UV radiation from sunlight before it reaches Earth’s surface. It serves as a global sunscreen ^O^

-          The first problem sign that scientist found about ozone layer was a gap or hole in the ozone layer over Antarctica during winter. Later, A researcher team published data showing that gases called chlorofluorocarbons, or CFCs, could damage the ozone layer.

·         Today, most uses of CFCs are banned.

-          All life on Earth depends on climate condition such as temperature and rainfall. But since late nineteenth century, average atmospheric temperatures on Earth’s surface started to increase.

·         The term used to describe this increase in the average temperature of the biosphere is global warming.

-          The most widely accepted hypothesis from the researchers is that current warming is related to the Earth’s changing climate, at least in part, to human activities that are adding carbon dioxide and other greenhouse gases to the atmosphere.

·         Concentrations of carbon dioxide in the atmosphere have been rising for 200 years. As a result, the atmosphere’s natural greenhouse effect is intensified causing the atmosphere to retain more heat.

-          Researchers use computer models based on data to predict effects of global warming. The new information from them helps provide society with ways of dealing with climate change.

-          People can make wise choices in the use and conservation of resources so that we can help maintain the health of the biosphere.

Ps. Sry for any mistakes na … T T  GOOD LUCK KA !!


download link !! [[meee pix duay na this RS ^O^]]
http://upload.one2car.com/download.aspx?pku=3A73D19F12X9A1IIW8Q66[TBCR2KNI


แค่ขอบคุณอ่ะ .. ให้กันได้ใช่มะะ ?? T T