Chapter Menu

1
Chapter Menu
Lesson 2 Populations and Communities
2
Lesson 2 Reading Guide - Vocab
Populations and Communities

• limiting factor
• biotic potential
• carrying capacity
• habitat

• niche
• symbiotic relationship

3
Lesson 2-1
Populations

• The area in which a population lives can be very
  large, such as the population of all the fish in
  the ocean, or very small, like fish in a lake.
• If either biotic or abiotic factors that affect
  an organism change, that organisms population
  can also change.

4
Lesson 2-1

• The area a population lives in can be large or
  small.

5
Lesson 2-1
Populations (cont.)

• Sometimes the size of a population changes
  because the ecosystem changes.
• Population density describes the number of
  organisms in the population relative to the
  amount of space available.
• If a population is very dense, organisms might
  have a hard time finding enough resources to
  survive.

6
Lesson 2-1

• The size of a population can change in different
  ways.

7
Lesson 2-1

• Limiting factors are factors that can limit the
  growth of a population.

8
Lesson 2-1
Populations (cont.)

• Biotic potential is the potential growth of a
  population if it could grow in perfect conditions
  with no limiting factors.
• Carrying capacity is the largest number of
  individuals that can survive in an area over a
  long time.
• The limiting factors of an area determine the
  areas carrying capacity.

9
Lesson 2-1
Populations (cont.)

• Overpopulation is when a populations size grows
  beyond the ability of the area to support it.
• This often results in overcrowding, a lack of
  resources, and an unhealthy environment.

10
Lesson 2-2
Communities

• All the populations in the same area interact as
  a community.

11
Lesson 2-3
Symbiotic Relationships

• Each population has different ways to stay alive
  and reproduce.
• All of the populations in a community share a
  habitat, the physical place where a population or
  organism lives.
• A niche is the unique ways an organism survives,
  obtains food and shelter, and avoids danger in
  its habitat.

12
Lesson 2-3
Symbiotic Relationships (cont.)

• A symbiotic relationship is one in which two
  different species live together and interact
  closely over a long period of time.
• These relationships can be beneficial to both
  organisms, beneficial to one and harmful to the
  other, or beneficial to one and neutral to the
  other.

13
Lesson 2-3
Types of Symbiotic Relationships

• Mutualismtwo species in a community benefit from
  the relationship.
• Parasitismone species (the parasite) benefits
  while another (the host) is harmed.
• Commensalismone species benefits and the other
  is neither helped nor harmed.

14
Lesson 2 - VS

• The factors that limit the size a population of
  organisms can reach are called limiting
  factors.
• A habitat is the physical environment where a
  population of organisms lives.
• A symbiotic relationship exists when two
  different species of organisms live together in a
  close relationship over a long period of time.