This document provides an overview of ecology and population ecology. It defines ecology as the study of interactions between organisms and their environment. It describes different levels of ecological organization from cells to biomes. It explains abiotic and biotic factors in ecosystems and how organisms are adapted to environmental conditions. The document also covers energy flow through ecosystems via food chains and webs. Finally, it discusses concepts in population ecology like population growth models, limiting factors, and density-dependent and density-independent regulation of populations.

1. An Introduction To Ecology
Chapter 18

2. 18.1
 Ecology – study of interactions
between organisms and
environment.
 Consists of abiotic (nonliving;
i.e. temperature, light, etc) and
biotic (living) factors.

3. Levels of Organization
The levels of
organization are
designed to allow
scientists to
understand and
study relationships
more easily

4. Levels of Organization
smallest unit
of living
things
group of
similar cells
organized to
work together
group of
different
kinds of
tissues
working
together
group of
organs
working
together
one individual
living thing
all organisms
of the same
kind living in
one area
all interacting
populations in
an ecosystem
all living and
nonliving
things
interacting
within a
certain area
large region
with typical
plants and
animals that
includes
several
ecosystems
cell

5. Species – a group of organisms
that can breed and produce fertile
offspring

6. Populations – groups of
individuals that are the same
species and living in the same area

7. Communities – a group of
organisms of different species living
together in the same area

8. Ecosystems – all the populations
living together with the nonliving
environment

9. Biomes – groups of similar
ecosystems that have similar
climates and similar communities

10. Biosphere – combines all the
parts of the earth in which life
exists

11. Ecology

12. 18.2 Components of an Ecosystem
Abiotic – the nonliving components of an ecosystem
 Light – affects photosynthesis
 Temperature – affects metabolism
 Water supply
 Oxygen supply
 Minerals
 Soil/Rocks
 pH

13. Examples of Abiotic
Factors

14. Biotic – the living components of
an ecosystem
 Plants
 Animals
 Protists
 Fungus
 Bacteria

15. Examples of Biotic
Factors

16. Organisms in a changing
environment
 Each organism can survive within a limited
range of environmental conditions
 Tolerance curve- a graph of performance
versus values of an environmental variable
such as temperature
 Acclimation- the process of an organism
adjusting tolerance to abiotic factors

17.  Organsims can survive unfavorable
environmental conditions through:
Dormancy- entering a state of reduced
activity
Migration-moving to a favorable habitat

18. Structure
Habitat – the physical area in which an
organism lives (includes climate,
topography, soil and water chemistry,
plant and animal life, etc.)
Niche – the way of life of a species
(includes its habitat, feeding habits,
reproductive behavior, etc.)
species can be generalists (broad
niche) or specialists (narrow niche)

19. 18.3 Energy Transfer

20. All energy comes from the sun
Plants harness the sun’s
energy in which process?

21. Plants need light for
photosynthesis, what else do they
need?
We call plants producers
because they produce
energy from the sun

22. Measuring productivity
Gross primary productivity-rate at
which producers in an ecosystem
capture energy of sunlight by
producing organic compounds
Biomass-organic material produced in
an ecosystem
Net primary productivity-rate at which
biomass accumulates

23. Primary Producers (Autotrophs)
 Energy from the sun is captured
by plants, algae, or bacteria
through photosynthesis.
 Energy from chemicals is
captured by some bacteria
through chemosynthesis.
 Capture energy from the sun or
from chemicals and store it in
the bonds of sugars, making it
available to the rest of the
community Did You Know? Deep-sea vents, far from sunlight,
support entire communities of fish, clams, and
other sea animals, which depend on energy
converted through chemosynthesis.

24. Consumers (Heterotrophs)
Rely on other organisms for energy
and nutrients
Use oxygen to break bonds in sugar
and release its energy through cellular
respiration (primary producers do this,
too)
Types of Consumers:
 Herbivores: plant-eaters
 Carnivores: meat-eaters
 Omnivores: combination-eaters
 Detritivores and decomposers:
recycle nutrients within the
ecosystem by breaking down
nonliving organic matter
California Condor
Did You Know? Scavengers, such as
vultures and condors, are just large
detritivores.

25.  When one organisms eats another,
molecules are metabolized and energy is
transferred
 An organism’s trophic level indicates the
organism’s position in a sequence of
energy transfers

26. Trophic Levels

27. Energy in Communities
 An organism’s rank in a
feeding hierarchy is its trophic
level.
 Primary producers always
occupy the first trophic level of
any community.
 In general, only about
10% of the energy available at
any trophic level is passed to
the next; most of the rest is
lost to the environment as
heat.
Lesson 5.3 Ecological Communities
Pyramid of Energy

28. What is a food chain?
 Food chain: Linear series
 of feeding relationships

29. A Basic Food Chain
Plants absorb light from the
sun, which is turned into
energy to grow. We call
these producers.
The vegetarian animals eat
the plants, they are called
primary consumers.
Secondary consumers
prey on primary
consumers.

30. Food Web- interrelated food chains in an ecosystem

31. MATTER CYCLING IN
ECOSYSTEMS
 Nutrient Cycles: Global Recycling
 Global Cycles recycle nutrients through the
earth’s air, land, water, and living organisms.
 Nutrients are the elements and compounds
that organisms need to live, grow, and
reproduce.
 Biogeochemical cycles move these substances
through air, water, soil, rock and living
organisms.

32. Covered in Photo/Resp. Chapter!

33. Water Cycle Key Terms:
 Ground water-water found in soil or in
underground formations of porous rock
 Transpiration-process by which water
evaporates from leaves of plants in
terrestrial ecosystems
 Evaporation-adds water to the atmopshere
 Precipitation-the process by which water
leaves the atmosphere

34. Water Cycle

35. Carbon Cycle
 Fourth most abundant element in universe
 Building block of all living things
 Main Pathway– in and out of living matter

36. Key Terms
Carbon Cycle- Circulation of carbon
through ecosystems
Carbon- A non-metallic element found in
coal, petroleum and natural gas. Major
component of life.
Soil Respiration- Carbohydrates are
oxidized and returned to the air by soil
microorganisms that decompose dead
animals

37. Key Terms Continued
Atmosphere- layer of gasses
Fossil Fuels- Carbon-rich fuel from ancient
animals and plants
Photosynthesis- Energy (sun)+ Water+
Carbon dioxide Carbohydrates+ Oxygen
Cellular Respiration- Glucose+ Oxygen
CO2+ H20+ Energy (ATP)
Decomposition- breakdown of matter by
bacteria and fungi

38. Biological Importance of Carbon
 All living organisms contain carbon
 CO2 is found in all living organisms
 Plants use carbon dioxide and water to
form simple sugars (photosynthesis)
 Carbon is needed for life
 Carbon dioxide is a greenhouse gas
 Carbon is necessary for life, but carbon
dioxide can be harmful

39. Carbon Cycle

40. Nitrogen cycle
 Organisms need nitrogen to make proteins and
nucleic acids
 Nitrogen gas makes up 78% of the atmosphere
 Most plants can only use nitrogen in the form of
nitrate
 Nitrogen fixation- process of converting nitrogen
gas into nitrate
 Nitrogen fixing bacteria transform nitrogen into
a usable form

41. Recycling nitrogen
 Decomposers break down decaying organisms
and release the nitrogen they contain as NH3
 Ammonification- changing NH3 (ammonia) into
NH4
+(ammonium)
 Nitrification-soil bacteria take up ammonium and
oxidize it into (nitrites) NO2
-and (nitrates) NO3
-
 Denitrification-process where anaerobic bacteria
break down nitrates and release nitrogen gas
into the atmosphere

42. Nitrogen Cycle

43. Importance of the Phosphorus
cycle
 Phosphorus is an essential nutrient for
plants and animals
 It is a part of DNA-molecules and RNA-
molecules, molecules that store energy
(ATP and ADP)
 Phosphorus is also a building block of
certain parts of the human and animal
body, such as the bones and teeth.

44. Difference in the Phosphorus cycle
 The phosphorus cycle differs from the
nitrogen and carbon cycles because
phosphorus is unable to achieve the
gaseous state in the atmosphere.
Phosphorus is mainly found in water, soil
and sediments. In the atmosphere,
phosphorus is found as fine dust particles.

45. By: Jermaine Loutin (Jose Marti Six Form
Envi.)

46. The Phosphorus Cycle

47. Ch 19 Populations
19.1 Understanding populations
 Population ecology: studies changes in population size
and the factors that regulate populations over time
A. Populations are affected by size, density and dispersion
1. Population size- number of individuals
2. Population density: the number of individuals of a
species per unit area or volume
 Ex: number of earthworms per cubic meter of soil
 Normally determined by sampling
 Estimates are more accurate for larger populations

48. 3. Population dispersion
a. Clumped dispersion pattern: individuals are
grouped in patches
 Most common in nature
 Due to unequal distribution of
resources in the environment
b. Uniform dispersion pattern: even spreading
 Usually results from interaction
between individuals
 Ex: territories
c. Random dispersion pattern: unpredictable
spacing
 Ex: plants grown from
windblown seeds

49.  B. Population dynamics: interactions between biotic
and abiotic factors that cause variation in population
size
 1. Population growth
 Population increases occur through birth (natality)and
immigration
 Immigration-movement of individuals into a population
 Population decreases occur through death (mortality) and
emigration
 Populations are also affected by life expectancy or how
long and individual is expected to live
 Emigration-movement of individuals out of a population
 May be influenced by factors such as food availability and water
quality

50. 2. Age structure-distribution of individuals
among different ages in a population

51. 3. Patterns of mortality
Survivorship: the chance of an individual in
a given population surviving to various
ages
 Survivorship curves: plot survivorship as
the proportion of individuals from an initial
population that are alive at each age
 Allows for species comparison

52. a. Type I survivorship: animals
that produce few offspring and
nurture them to maturity
 Ex: humans and other large
mammals
b. Type III curve: opposite of a
Type I
 Many offspring are produced
but few make it to maturity
 Ex: many invertebrates
c. Type II curve: survivorship is
constant over the lifespan
 Individuals are equally
vulnerable at every stage of
the life cycle
 Ex: lizards and rodents

53. 19.2 Measuring Populations
A. Population size
 Determined by the following equation:
 Growth rate =(individuals added)- (individuals
subtracted)
or
 (birthrate + immigration rate) – (death rate + emigration
rate)
 Growing populations have a positive growth rate;
shrinking populations have a negative growth rate.
 Usually expressed in terms of individuals per 1000
 Population changes are expressed as percentages:
 Growth rateX100= % growth

54. B. Exponential growth model:
the rate of population
growth under ideal
conditions
 As the population size grows,
more individuals are added
during each interval
 Graphing this data gives a J-
shape curve
Exponential growth can NOT
continue indefinitely
 Eventually, one or more
environmental factors will
limit growth
 Ex: space and food supply

55. C. Logistic growth model: idealized
population growth that is slowed by
limiting factors as the population size
increases
 Results in formation of an S-shape
curve
 K is the carrying capacity - maximum
population size that a particular
environment can sustain
 K varies depending on the species
and the resources available
 Influenced by predators, parasites,
food sources, and abiotic factors
 Emphasizes that resources are finite
 At low populations, resources are
abundant and the population is able
to grow nearly exponentially
 Population stabilizes at the carrying
capacity when the birth rate equals the
death rate

56. D. Population Regulations
Density-independent factors- factors that reduce the
population by the same proportion. Influence does not
change with population density.
 These are usually abiotic factors
 They include natural phenomena, such as weather
events
 Drought, flooding, extreme, heat or cold, tornadoes,
hurricanes, fires, etc.
Density-dependent factors- Influence changes with
population density.
 Any factor in the environment that depends on the
number of members in a population per unit area
 Usually biotic factors, these include:
 Predation, Disease, Parasites, Competition