Chapter 35: Population and Community Ecology
Concept 35.1: A population is a local group of organisms of one species
I. Defining Populations
A. A populations size is determined by the _______________ and space, weather
conditions, and __________________________
B. When scientists study populations they must determine its
________________________, such a lake, a state or the whole country
II. Population Density
A. Population Density is the _____________________________
______________________________________________________
B. Population density is useful when comparing two populations in different areas
III. Sampling Techniques
A. Since it is impossible to count every member of a population scientists use sampling
techniques to estimate the size of a population
1. _________________________- scientists mark off a square boundary at
several locations and take an average
2. Indirect Counting_____________________________
__________________ instead of the organisms themselves
3. ________________- scientists trap and mark individuals
B. Most sampling techniques involve making __________________ about the
populations being studied
Concept 35.2 -There are limits to population growth
I. Exponential Growth of Populations
A. A population’s ability to grow partly depends on the ________ which its organisms
can ____________________________
B. ________________________________ is when the population multiplies at a
constant factor at constant time intervals i.e. bacteria doubling every 20 minutes
II. Carrying Capacity
A. A population may start to grow exponentially, but eventually one or more
environmental factors will limit its growth
B. A ________________________________________ is a condition that can restrict a
population’s growth
C. The carrying capacity is ___________________________
___________________________________________________
III. Factors Affecting Population Growth
A. ________________________________________ is a factor that limits a population
more as a population density increases
B.
Density-Independent Factors are factors that limit population but are
____________________________________________
IV. Population Growth Cycles
A. A “boom” and “bust” growth cycle is one that _____________ rapidly followed by a
____________________________
B. Other growth cycles are influenced by those of other populations in their
environments
V. Survivorship curves are graphic representations of the age structure of a given population.
They are used to predict the future growth of the population.
A. Type_____ - reflect relatively low death rates early in life and through midlife, with a
sharp increase in death rate among older-age groups (e.g., _____________________).
B. Type ______ - illustrate a fairly even mortality rate throughout the life span of the
organism (e.g., ______________________________________________________).
C. Type _______ - Populations with high death rates early in life followed by a sharp
decline of death rates for the survivors are represented by Type III survivorship curves
(e.g., _______________________________________________________________).
Survivorship Curves- Type I, II, & III
Concept 35.3-Biologists are trying to predict the impact of human population growth
I. History of Global Population Growth
A. For most of human history, the human population has grown
__________________________________________
B. Human population growth depends on _______________ rates and ____________
rates
C. The introduction of ________________ has provided a stable
___________________________ so birth rates have gone up
D. Advances in _____________________________________
______________________ have caused death rates to go down
E. These factors have caused the human population to increase dramatically
II. Predicting Future Population Growth
A.
The ___________________________ of a population is the
proportion of people in different age groups
B.
Prediction of future growth varies because of the difficulty predicting future
________________ rates of various countries
C.
The question remains whether or not Earth will have the capacity for the human
population
Concept 35.4-Species interact in biological communities
I. Competition Between Species
A.
B.
C.
D.
Members of a population may compete for the same limited resource
Within a community, ________________________ takes place when two or more
species rely on the same limited resource
__________________________________________________
__________________________________________________
_______________________________ competitive exclusion
A ____________________includes an organisms living place, its food source, the
time of day it is most active and many other factors that are specific to that
organism’s way of life
II. Predation
A. Predation ________________________________________
B. Eating and avoiding being eaten are important to survival and predators and prey
have developed many adaptations
1. Predator adaptations include: _____________________
_____________________________________________
_____________________________________________
_____________________________________________
2. _______________________ include: retreating or fleeing from predators,
camouflage, defensive coloring, mimicry, secreting poisonous chemicals,
having spines and thorns
III. Symbiotic Relationships
A. A symbiotic relationship is when two species _____________
________________________________________________
B. There are three main types of symbiotic relationships
1. _____________________- A parasite gets it’s food at the expense of another
organism, i.e. mosquitos and humans
2. ________________________- Both organism benefit from the relationship,
i.e. E.Coli and humans
3.
_________________________- One organism benefits and the other is
neither hurt nor helped, i.e. sharks and remoras
Concept 35.5-Disturbances are common in communities
I. Disturbances to Communities
A. Natural Disturbances are events such as ________________
_________________________________________________
_________________________________________________
B. Disturbances can be either positive or negative
C. ________________also have an impact on communities which can be either
positive or negative
II. Ecological Succession
A. The ___________________________________________, often following a
disturbance is known as ecological succession
B. There are two types of succession:
1.
2.
Primary succession which is when new community arises from
_________________________________ i.e. plants growing on a volcanic
island
Secondary succession is when ____________________
______________________ i.e. a forested are which has
been cleared and abandoned
III. Human Activities and Species Diversity
A. ______________ of the Earth’s land is used by humans, mainly for cropland or
rangeland
B. Humans usually have a negative effect on species in two ways
1. ___________________________- Humans clear vast amounts of land to
make way for farming and building
2. _____________________________________ are species that are moved
from one location to another either accidentally or on purpose. These new
species may take over an area and prey on native species or drive them from
their niches