CHAPTER 34: The Biosphere: An Introduction to Earth’s Diverse Environments & CHAPTER 36: Population Ecology

CHAPTER 34: The Biosphere: An Introduction to Earth’s Diverse Environments

Sections 34.1 – 34.4: The Biosphere

• Ecology: the scientific study of the interactions of organisms with their environment

• An environment is complex, so organisms can be affected by many different variables:

  • Biotic factors: living components of the environment

    • includes organisms

  • Abiotic factors: nonliving components of the environment

    • includes physical features, chemical factors, temperature, forms of energy, water, nutrients

• Habitat: the specific environment an organism lives in and includes the abiotic and biotic factors present in its environment

• Levels of biotic organization smallest to largest:

  • Organism level: how one kind of organism meets challenges and opportunities  of its environment through its physiology or behavior

  • Population: a group of individuals of the same species living in a particular geographic area

  • Community: the assemblage of all the populations of organisms living close enough for potential interaction

  • Ecosystem: the biotic and abiotic components of the environment

  • Biosphere: an area extending from the atmosphere several kilometers above earth to the depths of the ocean; all of Earth that is inhabited by life

• Silent Spring by Rachel Carson

  • spread attention to the DDT pesticide issue that harmed the entirety of Earth

• All organisms require a source of energy to live

  • sunlight for photosynthetic organisms

  • chemical power from bacteria

• Temperature is an important abiotic factor because of its effect on metabolism

  • too low temperatures = very low metabolism

  • too high temperatures = took much metabolism; destroys enzymes

• Water is essential for all life

• I’m going to be really honest: I have no idea what to write for this section (34.4).  It’s purely applicational from the terms aforementioned, and I’m not focusing on the application-study part as of right now, so, err …

CHAPTER 36: Population Ecology

Sections 36.1 – 36.8: Population Structure and Dynamics

• Population: a group of individuals of a single species that occupy the same general area

  • these individuals rely on the same resources, are influenced by the same environmental factors, and are likely to interact and breed with one another

• Population ecology: ecology concerned with changes in population size and the factors that regulate populations over time

  • a population ecologist might use statistics such as the number and distribution of individuals to describe a population and its dynamics

  • data from population ecology is used to manage wildlife populations, develop sustainable fisheries, and gain insight into controlling the spread of pests and pathogens

• Population density: the number of individuals of a species per unit area of volume

  • estimates are used to count individuals in a population

    • can estimate a population by a count of individuals on one sample plot (size can be around 1 km^2

  • sometimes estimates are not based off counting organisms but by indirect indicators

    • bird nests, rodent burrows, etc

  • Dispersion Pattern: the way individuals are spaced within their area

    • Clumped Dispersion Pattern: individuals are grouped in patches; most common in nature

      • results from unequal distribution of resources in the environment

• Uniform Dispersion Pattern: results from interactions between the individuals of a population

  • results from territorial behavior or competition for resources

• Random Dispersion Pattern: individuals in a population that are spaced in an unpredictable way, without a pattern

  • very rare because of varying habitat conditions and social interactions

• Life tables: tracks survivorship/the chance of an individual in a given population surviving to various ages

• basically predictions on how long a population will live

• life tables can be used to construct survivorship curves

  • Survivorship curves: graphs that plot survivorship as the proportion of individuals from an initial population that are alive at each age

    • Type I Survivorship: most people survive older age intervals, but survival dramatically decreases around the highest intervals of age

      • usually species that produce few offspring but give them good care

    • Type II Survivorship: lifespan decreases at a constant rate

      • individuals are no more vulnerable at one stage of their life than at another

    • Type III Survivorship: low survivorship for the very young, followed by a period when survivorship is high for those few individuals who live to a certain age

      • usually species that provide large numbers of offspring but provide little care for them

• Population size fluctuates as new individuals are born or immigrate into an area and others die or emigrate

  • some populations are constant (trees, for instance)

  • some populations change rapidly (bacterium that undergo mitosis extremely quick, for instance)

• Exponential growth: the rate of population increase under ideal conditions

  • G= rN

    • G stands for growth rate of the population

    • N stands for population size (number of individuals in the population at a particular time)

    • r stands for per capita rate of increase

      • Per Capita Rate of Increase: the average contribution of each individual to population growth)

    • For example …

      • A population of rabbits has 100 individuals, and there are 50 births and 20 deaths in one month.  Therefore, the net increase is 30 rabbits.  The per capita increase in the population is 0.3.

        • Equation-wise, it would be: G = 0.3(100).  Here, you are trying to find the growth of the population, so distribute 0.3 to 100 to find the growth rate, which is G = 30.

    • Exponential Growth Model: an idealized picture of unlimited growth; no restriction on organisms ability to live, grow, and reproduce

      • realistically, any population will eventually be limited by the resources available

• Logistic Growth Model: a description of idealized population growth that is slowed by limiting factors as the population size increases

  • Limiting factors: environmental factors that restrict population growth

  • G = rN (K-N)K

    • K represents carrying capacity

      • Carrying Capacity: th emaximum population size that a particular environment can sustain

      • varies depending of species, resources available in the habitat, interactions with other organisms in their communities, predation, parasites

• The logistic growth model predicts that population growth will slow and eventually stop as population density increases only if either birth rate decreases and death rate decreases, or both

• Density-dependent Factors: limiting factors whose intensity is related to population density

  • Intraspecific Competition: competition between individuals of the same species for limited resources

• Density-independent factor: a population-limiting factor whose intensity is unrelated to population density

  • includes seasonal changes, climate changes, any abiotic factor

• Some populations (insects, birds, mammals, etc) undergo dramatic fluctuations in density with remarkable regularity

  • can be characterized as a “boom-and-bust” cycle

    • Boom as in rapid exponential growth

    • Bust as in the population falls back to a minimal level

• Life history: the traits that affect an organism’s schedule of reproduction and death make up its life history

  • includes the age of first reproduction, the frequency of reproduction, the number of offspring, and the amount of parental care given

  • r-Selection:environments where resources are abundant, thus permitting exponential growth

  • K-Selection: a reproductive strategy where species produce fewer offspring but invest more care in each one

• Sustainable Resource Management: harvesting crops without damaging the resource

CHAPTER 36: Population Ecology

Sections 36.9 – 36.11: The Human Population

• Imbalance of births and deaths is the cause of population growth or decline

• The number of people added to the population each year has been declining since the 1980s

• Demographic Transition: a shift from birth rates and deaths rates that are high but roughly ewual to birth and death rates that are low but roughly equally

• Age Structure: the number of individuals in different age-groups

  • Fertillity Rate: the average number of children produced by a woman over her lifetime

  • Population Momentum: the increased proportion of women of childbearing age in the population

• This section (36.10: Age structures reveal social and economic trends) is generally self-explanatory based off the title itself.

• Humans need to consume more and more resources as their population grows exponentially

• Ecological footprint: an estimate of the land and water area required to provide the resources an individual or nation consumes

  • includes fuel, food, housing; and the waste products: carbon emissions