1. Unit 12—Ecology (& Populations)
300
Ch 27
Ch 28
Unit 12—Ecology (& Populations)

2. Populations, Communities, & Ecosystems
What is a population?
All organisms of same species living in an area
What is a community?
All different populations living in an area
What is an ecosystem?
A community interacting with the abiotic (non-living) factors in an area
Picture  organism = one fish, population = all fish of same type, community = all different organisms, ecosystem = all different organisms & non-living (abiotic) factors

3. Population Size & Arrangement
How can populations be counted?
animals
ear tags
leg bands
radio transmitters
plants
marked w/ paint or ribbons
What if a population is too large to count every individual?
estimate using sampling techniques
count # in a small area, then multiply by total area
mark & recapture
Animals w/ tags, bands, transmitters can be followed back to shelter/nest & additional individuals can be counted
Count organisms in a small area (ex. 1 m2) & then multiply by the total area (ex. 10 m2)
mark and recapture method involves marking a number of individuals in a natural population, returning them to that population, and subsequently recapturing some of them as a basis for estimating the size of the population at the time of marking and release
m (# marked in recaptured sample) / n (total in recaptured sample) = M (# marked initially in total pop) / N (total pop. size estimate)
Or N (total pop. size) = n (total in recaptured sample) * M (# marked initially in total pop)
m (# marked in recaptured sample)
Mark & Recapture Simulation
Mark & Recapture Game

4. Population Size & Arrangement
How can a population distributed/ arranged in an area?
random
uniform
clumped
What might be an advantage of a clumped population?
food/shelter, protection from predators…. Plants can be protected from strong winds…
What might be an advantage of a clumped population (such as herds, flocks, schools)? Individuals may help one another find food/shelter, protection from predators…. Plants can be protected from strong winds…
What type of population distribution can be seen in the US?
What type of population distribution can be seen in CT?

5. Population Size & Arrangement
What is population density?
# individuals/area
Ex people/mile2

6. Population Changes What can cause a change in population size?
births
immigration
deaths
emigration
Can you come up with an equation to show overall population change?
Population change = (B + I – D – E) or (B + I) – (D + E)
Is population decreasing or increasing if change is:
positive?
increasing
negative?
decreasing

7. Visualizing Population Structures & Predicting Future Changes
population pyramids (a.k.a. age structure diagrams)
basic shape can help us predict what’s going to happen to the population in the future…
What do you think will happen to the population in each pyramid???
Ages 0-14
Ages 45+
Ages 15-44
How Population Pyramids Are Made Video
Population Pyramid TED video
Triangle Larger base (more pre-reproductives) than top (post-reproductives) means population is going to grow in the future (positive growth The wider the base, the faster the growth
Inverted (upside down) triangle  narrower base (fewer pre-reproductives) than top (post-reproductives) means the population is going to shrink in the future (negative growth)
Column  all groups are essentially equal in numbers, which means there will be remain stable (“zero population growth”…ZPG)
Rapid Growth
Guatemala
Kenya
Slow Growth
U. S.
Canada
Zero Growth
Spain
Greece
Negative Growth
Australia
Japan

8. Population Pyramids (Age Structure Diagrams)
Population growth rate by country
Population Pyramids (Age Structure Diagrams)
Census Bureau International Data-Pyramids
Developing Countries
wide base
high #s of pre- & reproductive age
high birth rates
fast growth
Developed Countries
slightly wider base, width is same, or inverted pyramid
lower #s of pre- & reproductive age
low birth rates
slow growth, zero growth, negative growth (pop. shrinks)
(less) developed countries (LDCs) (“third world”) = not industrialized or early stages of industrialization
(more) developed Countries (MDCs) (“first world”) = industrialized
the higher educational level of women, the lower the birth rate

9. Population Clock What event???
What event (mid 1700s to mid 1800s) spurred population growth???? Industrial Revolution (better living conditions ex. sanitation, health care & less need for lg # of children to work on family farm)

10. Population Growth Types of population growth: exponential growth
represents species’ biotic potential
ideal conditions (rare)
logistic growth
population reaches “carrying capacity”
common
point of maximum growth
Logistic Growth
Biotic potential is the maximum reproductive capacity of a population if resources are unlimited. Full expression of the biotic potential of an organism is restricted by environmental resistance, any condition that inhibits the increase in number of the population. It is generally only reached when environmental conditions are very favorable. A species reaching its biotic potential would exhibit exponential population growth and be said to have a high fertility, that is, how many offspring are produced per mother.
Exponential Growth In a population showing exponential growth the individuals are not limited by food or disease
Logistic Growth In most real populations, both food and disease become important as conditions become crowded. There is an upper limit to the number of individuals the environment can support. Ecologists refer to this as the "carrying capacity" of the environment. Populations in this kind of environment show what is known as logistic growth.
Exponential growth = J-curve, Restricted/logistic growth = S-curve

11. Population Growth Why don’t populations increase forever?
limiting factors
provide environmental resistance
prevent population from growing indefinitely
reach “carrying capacity”
can be:
abiotic (non-living)
biotic (living)
limiting factors circumstances or resources that limit growth, reproduction, or distribution of organisms
Abiotic Factors – nonliving factors that can limit the types and numbers of organisms in an ecosystem.
Biotic… living factors

12. Examples of Abiotic Limiting Factors
Abiotic Factors – nonliving factors that can limit the types and numbers of organisms in an ecosystem.

13. Abiotic Limiting Factors
Organisms have “range of tolerance” for abiotic factors
thrive (optimal range)
survive, but are not well (stress zone)
can’t survive (zone of intolerance)

14. Examples of Abiotic Limiting Factors
Abiotic limiting factors for desert plants & animals include…
temperature extremes
low availability of water
Have adaptations that aid survival…

15. Examples of Biotic Limiting Factors
living factors in an ecosystem
Living factors in an ecosystem
Usually described in terms of interactions
especially who eats whom or trophic levels

16. Biotic Limiting Factors
Decomposers are heterotrophs & must be part of every ecosystem to break down dead material & recycle nutrients!
usually described in terms of interactions
especially who eats whom or trophic levels
Primary producers = autotrophs (make own food… p’syn or chemosynthesis)
Consumers = heterotrophs (must take in food for energy)
Decomposers are HETEROTROPHS… digest food outside of self & absorb nutrients…. Break down dead material & recycle nutrients back to environment

17. Carnivores/omnivores
Energy Flow: Food Chains
heterotrophs
Fourth trophic level
Tertiary consumers
Carnivores/omnivores
Third trophic level
Secondary consumers
carnivores
Second trophic level
Primary consumers
herbivores
Primary producers = autotrophs (make own food… p’syn or chemosynthesis)
Consumers = heterotrophs (must take in food/nutrients for energy)
First trophic level
Primary producers
autotrophs
Decomposers are heterotrophs & must be part of every ecosystem to break down dead material & recycle nutrients!

18. Energy Flow: Food Chains
Food Web Interactive
Does energy only flow through individual organisms?
No… through community
in food chains & webs
***Arrow always points toward organism taking in energy & away from the organism “giving up” energy.
Does energy only flow through individual organisms? NO!!! energy doesn’t just flow through individual organisms; it also flows through communities of organisms, or ecosystems, and determines how organisms interact with each other and the environment.
Community – all of the biotic factors (organisms of different species) living in the same location – interacting and depending on one another.
Ecosystem - all the organisms living in a particular area, as well as all the abiotic (nonliving) components with which the organisms interact, such as air, soil, water, and sunlight
food chain  just one path of energy
food web  most/all possible paths of energy
Where do almost all communities get their energy? SUN is ultimate source b/c even though consumers don’t make own food, they eat producers or something that ate a producer
Where do almost all communities get their energy?

19. Energy Flow: Energy Pyramids
Energy cannot be recycled, it can only be transferred & transformed.
~90% is lost as heat &/or used by previous organism for life functions
~10% passed to next level
10% Rule of Ecological Efficiency
Amount of energy passed on to the next level.
Lost Energy 20 J 80
Pyramid of energy shows decrease of energy available to each higher trophic level
only 10% passed on Energy lost at each step mostly as heat % Rule of Ecological Efficiency
Nutrients are recycled ex. carbon cycle Energy is not.
Energy flow is one way – nutrients (raw materials) are cycled through an ecosystem
Ex. carbon cycle shows how carbon is cycled through the biosphere

20. Energy Flow: Food Chains
Another name for autotrophs?
producers
How do they get nutrients?
make their own food (sugars)
most by photosynthesis
What is the equation for photosynthesis?
What are the two processes by which they can make own food this?
Chemosynthesis (Archaea)
Photosynthesis (Protists, plants)

21. Energy Flow: Food Chains
Another name for heterotrophs?
consumers
How do they get nutrients?
absorption
ingestion

22. Energy Flow: Food Chains
Types of heterotrophs?
herbivores (eat plants)
carnivores (eat animals)
scavengers (feed on dead animals)
ex. vultures, buzzards, crabs
omnivores (eat plants & animals)
decomposers (break down dead material & recycle nutrients)
Must be part of EVERY ecosystem!

23. Nutrients in An Ecosystem
Nutrients can be recycled!
Biogeochemical or nutrient cycles
Ex. carbon cycle & nitrogen cycle
Decomposers play major role…
Energy flow is one way – nutrients (raw materials) are cycled through an ecosystem
Ex. carbon cycle shows how carbon is cycled through the biosphere
Carbon Cycle

24. Other Relationships in a Community
Predation
Competition
one organism benefits (predator), the other is harmed & usually killed (prey) (+, -)
both organisms are harmed (not necessarily killed) (-, -)
Predation: Unlike parasitism, the predator actually kills the prey
Competition: Notice both thrive as when separate, but population decreases when together

25. Other Relationships in a Community
symbiosis
when 2 species live closely together in a relationship over (a long) time
commensalism
mutualism
parasitism

26. Other Relationships in a Community: Commensalism
one partner benefits from the relationship & the other neither benefits, nor is harmed (+, 0)
Pic = Cattle egrets and livestock
An example of commensalism: cattle egrets foraging in fields among cattle or other livestock. As cattle, horses and other livestock graze on the field, they cause movements that stir up various insects. As the insects are stirred up, the cattle egrets following the livestock catch and feed upon them. The egrets benefit from this relationship because the livestock have helped them find their meals, while the livestock are typically unaffected by it.

27. Other Relationships in a Community: Mutualism
both partners benefit from the relationship (+, +)
Pollination in which nectar or pollen (food resources) are traded for pollen dispersal (a service)
One example is the relationship between sea anemones and anemone fish in the family Pomacentridae: the anemones provide the fish with protection from predators (which cannot tolerate the stings of the anemone's tentacles) and the fish defend the anemones against butterfly fish (family Chaetodontidae) which eat anemones.

28. Other Relationships in a Community: Parasitism
one partner benefits (parasite) & the other is harmed, but not usually killed (host) (+, -)
Parasite lives at the expense of the host
Host is rarely killed in this type of relationship (b/c then parasite wouldn’t have food source)