Transcript PA Standards:

PA Standards:
 4.1.7.A – Describe the relationships
between the biotic and abiotic
components of an ecosystem
 Describe symbiotic and predator/prey
relationships
73. Chapter 1 – Populations &
Communities
 Ecosystem – All living and nonliving
things that interact in a particular area
 Living things include bacteria, plants, and
animals
 Nonliving things include sunlight,
chemicals, soil, water, air, and man-made
items
Ecosystem Example
 What is living?
 What is nonliving?
 Name the
interactions.
74. A single ecosystem may contain
many “habitats”
 Habitat – where an organism lives and finds what it
needs to survive
 Example: A pond ecosystem includes several habitats –
the muddy bottom, the water, the bank, etc.
75. Parts of an Ecosystem:
 Biotic Factors – name given to
all the LIVING parts; the
interaction is often “eat or be
eaten”!
 Abiotic Factors – name given
to all the NONLIVING parts;
these supply the conditions for
survival (shelter, oxygen, water,
climate, etc.)
76. Organisms are grouped by
“species”
 Species – all those organisms that are
physically similar (look alike) and can
reproduce fertile offspring
Not all animals that can mate are the
same species! Ex: horse + donkey
 The offspring is a mule that can’t reproduce (infertile).
77. A species group is a “population”
 Population = all the members of one
species living together in a particular area
 One ecosystem contains many populations
 Ex: duck population, turtle population, etc.
78. A group of populations is a
“community”
 Community = all the different populations that live
together in an area
79. In a community living things
affect one another & their
surroundings
 Ecology – the study of how living things interact with
each other and the environment; this work is carried
out by an “ecologist”
American folk singer Pete Seeger recorded
this song about environmental interactions
 http://www.youtube.com/watch?v=UyGYXjyrvhY
80. “Population Density” is the
number of individuals found in a
specific area (or how tightly packed)
 It is calculated by dividing:

# of individuals
Area they inhabit
 Example: The population density of this classroom
might have been designed to be 1 student per meter2
81. Ways to Find Total Population Size
1) Counting:
a. by direct observation (seeing the animals with
your own eyes)
b. by indirect observation (seeing only the animals’
tracks or nests)
2) Sampling: count only the animals in a small area,
then estimate the rest
3) Mark & Recapture: captured animals are marked,
then released; when a new sample is captured, the
fraction of those w/marks can be used to calculate
total population
Example of Sampling:
 Bacteria are grown on the surface of agar (kind of
gelatin) in petri dishes; these microscopic cells form
colonies that show up as small spots on the agar. Often
too numerous to count, the scientist will count only a
sample of colonies(maybe ¼ the dish) and estimate
the rest.
 40 colonies x 4 =
 160 on the whole
 dish
Example of Mark & Recapture:
 You use nets to catch 100 blue birds.
 You put metal bands on the legs of all 100 and release
them.
 One month later you use nets again to catch blue
birds. In this new group you find that ½ already have
bands on their legs.
 This indicates that in the original group of 100 birds,
you really only caught ½ of the population in your
nets.
 Total population is then actually 200 birds.
82. What can Change Population
Size?
 1) Births:
When birth rate > death rate, population increases
 2) Deaths:
When death rate > birth rate, population decreases
 3) Immigration: individuals move in
 4) Emigration: individuals move out
83. What Controls Population Size?
 Limiting factors are environmental conditions that
can stop population growth.
 These include: food, space, and weather.
 Carrying capacity is the largest population that an
environment can support given its limiting factors.
Ecologists graph population data; this
graph shows human population
 Population grows steadily until resources run out.
Limiting factors are little food, no shelter, & disease.