Transcript Living Things - Ms. D. Science C.G.P.A.

Ch. 14.4
Ms. De Los Rios
7th Grade
Essential Question:
How Do Living Things Affect One Another?
How Do Populations Change in Size?
What Factors Limit Population Growth?
Populations
Pgs. 500-507
Vocabulary
1. Birth Rate- the number of births in a specific population in a certain time
period.
2. Death rate- The number of deaths in a specific population in a certain
time period.
3. Immigration- Movement of individuals into a population’s area.
4. Emigration- Movement of individuals out of a population’s area.
5. Population density- the number of individuals in an area of a specific
size.
6. Limiting Factor- an environmental factor that causes a population to
decrease in size.
7. Carrying capacity-the largest population that a particular
environment can support.
How Do Populations Change In Size? Pg. 500
Populations change in size when new members join the population or
when members leave the population.
Ecologist study pop. and monitor the sizes of pop. over time.
new members are born into it (join)
Populations change in size when:
or when members die (leave)
Birth and Deaths
The birth rate counts number of births in a population over a certain amount
of time. The death rate counts the number of deaths over a certain amount of
time.
Do the MATH!
The Population Statement pg. 502
•When the birth rate is greater than the death rate,
the population will generally increase.
Birth rate > death rate= population will generally
increase
•The population will generally decrease when the
death rate is greater than the birth rate.
Death rate > birth rate= population size decreases
For example, the white-tailed deer population in Iowa
decreased due to over-hunting.
Immigration and Emigration pg. 502
The population can also change when
individuals move into or out of the
population.
Immigration means moving into a population
Emigration means leaving a population.
Ecologists can graph how a population changes
over time.
Populations pg. 503
Changes in a Rabbit Population
This graph shows how the size of a rabbit population changed over ten years.
Fig. 2
Population
1.
In Year_______, the rabbit
population reached its
highest point.
2.
What was the size of the
rabbit population in that
year?_____________
3.
How do you think the rabbit
population affected the fox
population over the same
ten-year period. Explain your
reasoning._______________
_______________________
Population Density pg. 504
The population density is a measure
of all the individuals in one area at one
time.
Equation
Population Density= Number of ndividuals
Unit area
Populations pg. 504
Population Density of the Flamingos in the Pond
In the pond on the top, there are 10 flamingos in
s.
8 square meters. The population density is 1.25 flamingos per square meter.
1.
Calculate- What is the
pop. Density of the
flamingos in the pond on
the bottom?
2.
Infer- If 14 more flamingos
landed in the pond on the
bottom, what would the
population density be
then?
3.
Challenge- What do you
think would happen if the
population density of
flamingos in the pond on
the bottom became too
great?
Assess your Understanding
What Factors Limit Population Growth? Pg. 509
A limiting factor is something in the
environment that keeps a population from
growing or makes a population smaller.
Some limiting factors are:
foodshelter
water
space
disease
parasitism
predation
nesting sites.
Factors that Limit Population Growth pg. 505
When there is not enough food, shelter, or water for organisms to survive,
population growth can be limited. Limiting factors determine an area’s carrying
capacity.
Carrying capacity is the largest population that an area can support.
For example, a plant needs to grow in a large enough space to obtain the things it needs to survive.
Also, in densely populated areas disease can spread and infect close-growing plants.
Shelters provide for protection and survival, if organisms can’t find a shelter
they may die or lose their young (affecting the pop.)
Water- the quantity and quality of water can mean the difference between
life and death. (drought=less water= affects pop.)
Poor water quality= threatens living conditions= poor health
Figure 3
Populations pg. 505
Relate Cause and Effect
As you read about the four
factors that can limit
populations, think about
cause and effect.
Did You Know? Pg. 506
Some plants, like the black walnut tree, release chemicals into the
environment that prevent other plants from growing too close. This
process is called allelopathy (uh lee LOP uh thee).
Factors that Limit Population Growth Pg. 507
Size- space affects animal and plant populations. Amount of space
determines whether a plant can obtain light, water, and soil nutrients.
Disease- a limiting factor especially in densely populated areas. During
warm and rainy periods some crops can develop disease called early blight
(leaves rot and fall off killing the plant.)
Predation can limit the population sizes of prey, while parasitism can
reduce the size of the host population.
The availability of nesting sites also limits populations. Without room to
nest, offspring cannot be added to a population.
Figure 4
Apply It!! Pg. 507
Read pg. 507
•Write a letter to the editor that
describes how food and space
may be limiting factors for the
Florida panther. Add a headline
to your letter.
_______________________
_______________________
_______________________
_______________________
Assess your Understanding!