environmental science chapter 4. section 1 objectives: 1. describe the different levels of...
TRANSCRIPT
EnvironmentalScienceChapter 4
Section 1 Objectives: 1. Describe the different levels of
organization studied by ecologists
2. Explain the difference between biotic and abiotic factors.
3. Discuss how an organism’s habitat relates to its survial.
Section 1 The Central Case
How do changes in population size relate to environmental conditions?
Section 1 Scientists study life at many levels, from
individual organisms to the entire biosphere.
Lets begin by taking a look at those different levels……………
Section 1 Ecology (figure 1) –
Ecologist
Section 1 Levels of ecological organization 1. Individuals
What ecologists study:
2. Populations
What ecologists study:
Section 1 Species
3. Communities
What ecologists study:
Section 1 4. Ecosystems –
What ecologists study
5. The Biosphere
Section 1 Ecosystems include both biotic and
abiotic factors.
Biotic factors
Abiotic factors
Section 1 The specific environment in which an
organism lives is its ____________________.
It consists of both ________________ and ____________________ factors.
Anything an organism needs, including nutrition, shelter, breeding sites, and mates is a _________________________.
Section 2 Objectives: 1. Explain the usefulness of tracking
population size. 2. Describe population density. 3. Describe the 3 ways populations can
be distributed. 4. Explain what age structure diagrams
tell you about a population.
Section 2 The overall health of a population can
often be monitored by tracking how its size changes, population density changes, and distribution changes.
The number of individual organisms present in a given population at a given time is called the _______________________.
Section 2 If a population size increases or remains
the same it is a sign of a _______________________________________.
If a population size decreases it can lead to __________________________________.
The Passenger Pigeon
Section 2 Determining population size
Do you think Alexander Wilson actually counted 2 billion passenger pigeons???
NO!!!!
He took a SAMPLE
Section 2 They take a reasonable area, count the
number of individuals, and estimate the number of individuals of a much larger area.
Scientists also look for EVIDENCE that the organisms exist. Animal droppings or tracks
Section 2 The number of individuals within a
population per unit area describes the ____________________ ___________________.
High population densities Pros:
Cons:
Section 2 The number of individuals within a
population per unit area describes the ____________________ ___________________.
High population densities Pros:
Cons:
Section 2 Low population densities Pros:
Cons:
Section 2 How the organisms are arranged within
an area is called __________________ ___________________________.
Populations can be arranged ________________, ___________________, or in ____________________.
Section 2 Random distribution:
Uniform distribution:
Clumped distribution:
Section 2 Age structure and sex ratios This describes the relative numbers of
organisms of each age within a population: ___________ ________________.
______ ____________________ ____________ are visual tools to show the age structure of populations.
Section 2 Pre-reproductive organisms:
Post-reproductive organisms:
The proportion of males to females in a population describes _____________ __________.
Section 3 Objectives: 1. Describe the factors that influence a
population’s growth rate. 2. Explain exponential growth and
logistic growth. Explain how limiting factors and biotic
potential affect population growth.
Section 3 A population’s growth rate is
determined by births, deaths, immigration, and emigration.
The rate at which individuals are born is called _________________________.
The rate at which individuals die is called ___________________________.
Section 3 To show how the likelihood of death
varies with age, population ecologists use graphs called _______________ ___________.
There are 3 types of survivorship curves:
I: II: III:
Section 3 Population size can also be affected by
people moving in or out of a population. ____________ is the arrival of individuals
from outside a given area. _____________ is the departure of
individuals from a given area. _________________ is the seasonal
movement into and out of an area.
Section 3 Calculating Population Growth (individuals added)-(individuals
subtracted) = population growthOr
(birthrate + immigration rate)-(death rate + emigration rate) = population growth
Example:
Section 3 How populations grow Growth rates change depending on resources
available to the organisms in the population 2 ways for populations to grow: 1. 2.
1. _______________________ occurs when a population increases by a fixed percentage each year Produces a J-shaped curve on a graph
Section 3 1. _______________________ occurs when a
population increases by a fixed percentage each year
Produces a J-shaped curve on a graph Exponential growth occurs when:
1. 2. Examples:
1. Mold growing on bread 2. bacteria growing on dead organisms
Section 3 2. ___________________ describes how a
population’s initial exponential increase is slowed and finally stopped by limiting factors. Produces an S-curve on a graph ____________ are characteristics of the
environment that limit population. _____________ is the largest population size
a given environment can sustainably support.
Section 3 Limiting Factors and Biotic Potential _______________________ is a limiting
factor whose influence changes with population density Ex: competition, predation, disease
__________________ is a limiting factor whose influence is not affected by population density Ex: catastrophic events
Section 3 _________________ is the growth rate of a
population under ideal conditions Factors that affect the biotic potential:
1. 2.