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 type (species) living in an area
What is a community?
All different organisms (populations) living in an area
What is an ecosystem?
A community interacting with the non-living (abiotic) 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
What is a population? A group of organisms of the same species living in an area at the same time
What is a community? All the populations living & interacting in an the same area at the same time
What is an ecosystem? All communities in an area interacting w/ each other & the non-living (abiotic) factors in the environment

3. Population Changes What can cause a change in population size? births
immigration
deaths
emigration

4. 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
Animated Population Pyramid
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
Nigeria
Saudi Arabia
Slow Growth
U. S.
Australia
Canada
Zero Growth
Spain
Austria
Greece
Negative Growth
Germany
Bulgaria
Sweden

5. Population Pyramids (Age Structure Diagrams)
Population growth rate by country
Population Pyramids (Age Structure Diagrams)
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

6. Population Clock

7. Population Growth Types of population growth: exponential growth
represents species’ biotic potential
ideal conditions
logistic growth
population reaches “carrying capacity”
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

8. 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

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

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

11. 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

12. 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

13. 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 for energy)
First trophic level
Primary producers
autotrophs
Decomposers are heterotrophs & must be part of every ecosystem to break down dead material & recycle nutrients!

14. Energy Flow: Food Chains
Food Web Interactive
Does energy only flow through individual organisms?
No… through community
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?

15. 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

16. 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 is another name for autotrophs? Producers How do they get their nutrients? Make own food SUGAR!!!!!
What are the two processes by which they can do this? Chemosynthesis (Archaea) Photosynthesis (Protists, plants)
What was the equation for p’syn again???? light
6CO2 + 6H2O  C6H12O6 + 6O2
chlorophyll (glucose)
What is another name for heterotrophs? Consumers How do they get their nutrients? Must eat autotrophs or other heterotrophs
What categories can we break heterotrophs into? Herbivores, Carnivores (including scavengers that feed on dead animals), omnivores, decomposers (break down dead plants & animals & organic waste)

17. Energy Flow: Food Chains
Another name for heterotrophs?
consumers
How do they get nutrients?
absorption
ingestion
What is another name for autotrophs? Producers How do they get their nutrients? Make own food SUGAR!!!!!
What are the two processes by which they can do this? Chemosynthesis (Archaea) Photosynthesis (Protists, plants)
What was the equation for p’syn again???? light
6CO2 + 6H2O  C6H12O6 + 6O2
chlorophyll (glucose)
What is another name for heterotrophs? Consumers How do they get their nutrients? Must eat autotrophs or other heterotrophs
What categories can we break heterotrophs into? Herbivores, Carnivores (including scavengers that feed on dead animals), omnivores, decomposers (break down dead plants & animals & organic waste)

18. Energy Flow: Food Chains
Types of heterotrophs?
herbivores (eat producers/plants)
carnivores (eat consumers/meat)
scavengers (feed on already dead animals)
ex. vultures, buzzards, crabs
omnivores (eat both plants & animals)
decomposers (break down dead material & recycle nutrients)
Must be part of EVERY ecosystem!
What is another name for autotrophs? Producers How do they get their nutrients? Make own food SUGAR!!!!!
What are the two processes by which they can do this? Chemosynthesis (Archaea) Photosynthesis (Protists, plants)
What was the equation for p’syn again???? light
6CO2 + 6H2O  C6H12O6 + 6O2
chlorophyll (glucose)
What is another name for heterotrophs? Consumers How do they get their nutrients? Must eat autotrophs or other heterotrophs
What categories can we break heterotrophs into? Herbivores, Carnivores (including scavengers that feed on dead animals), omnivores, decomposers (break down dead plants & animals & organic waste)

19. Nutrients in An Ecosystem
Nutrients can be recycled!
Biogeochemical or nutrient cycles
Ex. carbon 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

20. Other Relationships in a Community
symbiosis
when 2 species live closely together in a relationship over time

21. 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.

22. 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.

23. Other Relationships in a Community: Parasitism
one partner benefits (parasite) & the other is harmed (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)

24. Other Relationships in a Community: Predation
one organism benefits (predator), the other is harmed (prey) (+, -)
Unlike parasitism, the predator actually kills the prey