BIOL202 - Lectures 1-4

BIOL202 - Lectures 1-4 - LECTURE 1: WHAT IS...

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LECTURE 1: WHAT IS "ECOLOGY?” The primary focus of the field of Ecology is explaining: - the distribution of organisms (where they are found) - the abundance of organisms (how many there are) More specifically, ecologists want to know how various environmental factors influence distribution/abundance Especially environmental factors that affect an organism's: survival, reproductive output , and growth If something in a particular environment can severely limit survival, reproduction and/or growth in a species, then we would not expect to find that species in that enviroment. On the other hand… ---------------- Can divide the relevant environmental factors into two main types: 1. abiotic factors : factors physical or chemical in nature e.g., temperature at different times of day/year amount/form of moisture available during the year average amount of sunlight structure of the soil - speed of current acidity of soil or water & availability of N, P, Ca, Mg, etc. amount of dissolved O 2 in water 2. biotic factors : those biological in nature, e.g., type/abundance of: different " prey" - predators - parasites - pathogens - competitors all of which can affect survival, reproduction and growth of individuals in a species (and hence D & A)
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Abundance and distribution of organisms can be studied at the… ….continental level ….regional/habitat type level ….microhabitat level E.g.: distribution of Horned Lark, a grassland bird species Why is the horned lark found only in the Midwest and West? And why in only certain parts of the Midwest and West? Within a patch of grassland, why are horned larks more common in areas heavily grazed by cows or buffalo as opposed to areas lightly grazed? Within a territory, why are certain areas used for nesting whereas other areas are not?
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LECTURE 2: THE NATURE OF POPULATIONS population: demography: the study of the size and structure of populations and the changes within them DEFINING CHARACTERISTICS OF POPULATIONS 1. Density and abundance - density: abundance = absolute number of individuals in population 2. Population stability - refers to: - population may: - be relatively stable (nonfluctuating) - be growing or declining - fluctuate erratically - cycle regularly between high/low abundance
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3. Pattern of dispersion of individuals - refers to the spacing pattern of individuals Clumped Uniform Random Random spacing quite uncommon in nature Uniform spacing also relatively uncommon - in animals, see this when: - in plants, see this when: Clumping by far most common pattern in nature. Many reasons why organisms may be clumped in space:
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4. Age-structure - -refers to number of individuals in population in various age classes -can dramatically influence on growth rate of population
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5. Sex ratio: number of male:female individuals Not all populations with 1:1 sex ratio: e.g. western Canada populations of elk: fetal sex ratio: 113:100 adult sex ratio ranges from: 85:100 to 37:100
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6. Age-specific pattern of survivorship To what age do individuals normally survive? Data usually presented in form of a
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This note was uploaded on 04/18/2008 for the course BIOL 201 taught by Professor Mechling during the Spring '07 term at Towson.

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BIOL202 - Lectures 1-4 - LECTURE 1: WHAT IS...

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