Unit 7
Intro to Ecology
Population dynamics
Videos :)
• http://www.youtube.com/watch?v=sc4HxPxNrZ0
• http://www.youtube.com/watch?v=DZT6YpCsapg
• https://www.youtube.com/watch?v=E8dkWQVFAo
A
Populations change over time….
• Today, we will talk about factors that cause
populations to change
Habitats versus Niches
• A habitat is all the biotic and abiotic factors in an
area where an organism lives.
• An ecological niche is composed of all the
physical, chemical, and biological factors that a
species needs to survive, stay healthy and
reproduce.
Habitat
VS
Niche
Warm-up:Quick sketch
Draw the habitat vs niche of an animal of your choice. Use your notebook.
Habitat
Niche
How do populations change?
• Think-Pair-Share: let’s say there’s a small
community of hedgehogs that live in a certain area.
What can happen to them to cause their population
to change?
• Immigration
• Emigration
• Deaths
• Births
Exponential growth
Questions to think about:
• What happens as time
goes by?
• Which one is the
DEPENDENT Variable and
which is the
INDEPENDENT variable?
• Is this a realistic
representation of how a
population will really
grow?
• Why or why not?
Logistic growth
What is Logistic Growth?
An ecosystem will
eventually run out of
resources to support
population growth.
Exponential growth
will stabilize and
become logistic
growth.
Carrying Capacity
Carrying Capacity: maximum number of organisms
an ecosystem can support.
What causes a population to reach its carrying capacity?
RESOURCES!
Videos :)
• https://www.youtube.com/watch?v=VcSX4ytEfcE
• http://www.youtube.com/watch?v=sc4HxPxNrZ0
• https://www.youtube.com/watch?v=E8dkWQVFAo
A
Density-dependent Factors
●
●
●
A limiting factor that depends on population size is called a
density-dependent limiting factor.
These factors operate most strongly when a population is large and
dense.
They do not affect small, scattered populations as greatly.
Examples
of
Density-dependent
Factors
1. Competition: animals competing for resources
2.
3.
Predation: animals being eaten by predators
Parasitism and Disease: A parasite lives in or on another organism (the
host) and harms it. Disease can also infect and kill an individual
Density-Independent Factors
Density-independent limiting factors affect all populations in similar ways,
regardless of the population size.
Examples of Density-Independent Factors
•
•
•
•
unusual weather
natural disasters
seasonal cycles
certain human activities—such as damming rivers and clear-cutting forests
Who’s infected?! Activity
In front of you are some cups of liquid. One person’s cup is
“infected” in each round.
Round one:
1.
2.
“Interact” with two people by pouring all of one person’s
liquid into the others and then redividing the liquid.
How many people are infected?
Round 2:
1.
2.
“Interact” with 4 people this time.
How many people ended up being infected?
Answer in teams
1.
How did the number of interactions you had affect the number of people
who were infected at the end?
2.
Is this activity an example of density-dependent or density-indepedent
limiting factors?
Biodiversity
Sustainability
https://www.youtube.com/watch?v=eEi
s6O9m0Ow
Cell Phones
https://www.youtube.com/watch?v=YM
zN_a66NKg
Biosphere
●
●
The part of earth where life
exists
All of the living organisms on
the planet Earth.
Biodiversity
Biodiversity is the variety of different species that inhabit a particular area.
Why is it important?
You tell me. Brainstorm with your table, write responses on post-its and post
up please.
So, why is it important?
Biodiversity’s benefits to society include contributions to:
●
●
●
●
Medicine: there are chemicals present in organisms that may lead to a
cure to many diseases (or even cancer)
Agriculture: there are plants and animals that may help us survive on the
planet.
Goods: more animals and plants leads to more goods.
Services: Many organisms like bees perform “services” that benefit us.
Loss of Biodiversity
https://www.youtube.com/watch?v=vCkDxD0DV0Q
Threats to Biodiversity
●
●
●
●
●
Hunting
Habitat reduction
invasive species
Pollution
Climate change
Ecosystems
What do you see?
Ecosystem
All of the organisms in
a community and the
non-living components
that accompany them.
Biotic vs Abiotic Factors
Biotic Factors
Abiotic Factors
Living things that are a
part of a community
The non-living things
that are a part of an
ecosystem.
Examples?
Examples?
Ecology
Ecology is the study of interactions among living things, and between living
things and their surroundings.
Recap
A niche is a range of physical and biological conditions in which a species lives
and the way it obtains what it needs to survive and reproduce.
Producers
What does it mean to produce something?
Can you think of an organism in an ecosystem which produces its own food?
Consumers
What does it mean to consume something?
Make a list of organisms that consume food.
Producers vs Consumers
Producers
Consumers
Also called Autotrophs
Also called
Heterotrophs
produce their own food consume food that was
by using things in their synthesized by another
environment
organism.
Competition
●
●
Since resources are limited, organisms compete for survival.
Competition helps determine the number and kinds of species in a
community and the niche each will occupy.
Predators
●
●
Hunt other animals for food.
They can drastically affect the size of prey
populations.
Herbivores
Are consumers who only eat plants.
They can affect the size of and distribution of plant populations
Symbiosis
A close ecological relationship between two or more species
Mutualism
When both species benefit from their interactions
Parasitism
One organism benefits while the other is harmed.
Commensalism
One species receives a benefit while the other is not harmed.
Ecosystems and change...
Under stable conditions, the number and types of organisms in an ecosystem
will remain relatively constant.
Disturbances in an ecosystem
….can cause some species to die out and others to move in.
●
●
Resilient ecosystems will return to their normal state after a minor
disturbance.
Some ecosystems will never return to their normal state and a new
ecosystem will arise after a major disturbance.
Human impact on ecosystem resilience
Before:
After
Before:
Will the ecosystems we just looked at ever
recover?
Why or why not? Discuss with your team?
Here are some ways that Humans have impacted
Ecosystems.
cd
Yellowstone
https://www.nps.gov/features/yell/webcam/oldFaithfulStreaming.html