Download Ecology and Population Biology

Ch. 47 and 48
Ted-ed: Making sense of how life fits together
Introduction:
Video
Habitat
Game
 Ecology: the study of interactions of organisms with
one another and their physical surroundings
Biosphere
 The part of the Earth where life
exists
 Includes:


All the areas of land, air and water on
the planet
All the life that populates these
 Extent:
 From about 8 km above the Earth’s
surface to 8 km below the ocean’s
surface
 The distribution of life is not
uniform:

Few organisms live in the polar
regions; many in tropics
Ecosystems
 Consist of :
 an area’s physical
features (abiotic factors)
 An area’s living
organisms (biotic
factors)
Eg: A Pond
Biotic factors
Abiotic Factors
 Fish
 Water
 Frogs
 Sunlight
 Insects
 Rocks
 Worms
 elevation
 Snails
 Rainfall
 Amebas
 Temperature
 Waterlilies
 Humidity
Ecosystem….
 Community
 The organisms living together in an ecosystem
 Ecosystems are connected by:
 Living features (pond crayfish are eaten by forest
raccoons
 Non living features (A river in the mountains meanders
through forest and grassland on its journey to the sea)
Ecological Succession
Why do ecosystems change over time?
 Because every organism affects environmental conditions
around it Video
 Eg: Trees - shade the area below their branches making it
cooler and darker
Due to these changes we see:
 Ecological succession – when an existing community of
organisms is replaced by a different community over time.
Time frame of succession?
 Can be only a few decades to thousands of years
 Succession can occur where no living community
already exists
 Example: a volcanic
island rising from the
sea
Pioneer Species
Organisms that colonize areas that are devoid of life
Lichens – pioneers on bare rock
 Produce acids that break down
rocks
 Over the years, make a thin soil
that supports mosses
 Mosses further change the soil allowing other plants to
grow
Changes make it possible for earlier species to continue
living there
 Succession can occur where natural disasters or human
activities wipe out existing communities
Climax community
 A fairly stable collection
of organisms described
by the most obvious
species present
 Determined partly by
chance
 If something happens, it
may return to the way it
was, or may never be the
same again
Energy and Nutrients:
Building the web of life
 Flow of Energy
 The ultimate source of
energy is the sun
 ANIMATION
 Photosynthesis:
 Green plants and bacteria
use sunlight to assemble
carbon dioxide and water
into carbohydrates
Energy Flow cont…
 Producers:
 Photosynthetic
organisms that make
their own food
 Primary Consumers
 Organisms which get
their food from
producers… also known
as herbivores
 Higher level consumer
 Organisms which get
their food from lower
organisms (aka.
carnivore)
Energy Flow through an Ecosystem
 Decomposers: Video
 Organisms that obtain
food from non-living
organic matter
 eg: bacteria and fungi
Trophic Levels
 Trophic= food
 At each higher trophic level, less
and less of the original energy is
available
 Energy is used to:
 Maintain metabolism
 Power daily activities
 What is left is changed into new
animal biomass
 About 10% of the energy at one
level can be used by animals at
the next
Ecological Pyramids
 Show the energy relationships among trophic levels
Pyramid of:
Shows:
Energy
Total energy at each level
Biomass
Total mass of living tissue at
each level
Numbers
Total number of organisms
at each level (not species)
Population Growth
 Introduction:
 A population (def’n): a group of organisms that belong
to the same species and live in a given area
Exponential Growth!
(A baby boom)
 Given ideal conditions, almost any organism will
experience a rapid increase in population
 The larger it gets, the faster it grows
 This pattern is called exponential growth curve
 This doesn’t continue in natural populations for long
 Sketch an exponential growth curve
Logistic Growth: A Step closer to
realty
 Most populations go through a number of phases of
growth
 Sketch and label a logistic growth curve
Populations:
 Grow when the birth rate is greater than the death
rate.
 Growth may slow because:
 The birth rate slows down
 The death rate speeds up
 Both
 Zero growth occurs when birth rate = death rate; this is
also called steady state.
 Steady state is not really steady because the population
rises and falls but it averages out at a certain size
 This problem represents the carrying capacity of an
of an environment for that species
 Factors that block further growth include:
 Lack of food
 Overcrowding
 Competition among individuals
48.2 Factors that control
population growth
 Density Dependent Limiting Factors
 Population limiting factors that operate on large
populations
 Occur when a population is large and crowded
 Competition
 Predation
 Parasitism
 Crowding and stress
Competiton:
 The struggle for food water, space and other life
essentials Battle at Kruger
Predation:
 Prey evolve defenses such as: poisons, camouflage,
shells
Predators evolve:
 Resistance to poisons
 Stronger teeth
 Stronger digestion
 Keener eyesight
As their populations cycle together,
 As prey population grows, it supports a larger predator
population
 As predators become more numerous, they eat more
prey increasing the prey death
 Predators begin to starve
 Prey survive better and begin to reproduce more
 The cycle begins again
 Animation
 Without a predator to keep numbers down,
introduced animals can quickly become serious pests!
Parasitism TED-Ed Parasites
 Parasites live off their hosts weakening them
 Crowding helps parasites travel from one host to
another
Crowding and Stress
 Space is needed for:
 Hunting
 Nesting
 Territory
 Many species will fight amongst themselves if
overcrowded
 Stress due to over-crowding can cause hormonal
changes in organisms
Density Independent Limiting
Factors
 Natural occurrences such as storms and weather
changes
 These can cause a population to boom and bust
regardless of its size at the time
48-3 Interactions within and
between communities
 Community: all the populations of organisms lving in
a certain area
 Populations within communities interact with one
another in many ways
 Example within the same species:
 Plant competition for water (intraspecies)
 Example between different species: predator compete
for prey (interspecific)
Symbiosis Video
 Relationships between organisms
 Parasitism – one species harmed while the other
benefits
 Eg: disease causing bacteria
 The bacteria reproduce in the human’s body making the
individual sick
 Commensalism
 One organism benefits and the other is unharmed


Eg: Shrimp live in the tentacles of anemones
Shrimp are protected from possible predators
 Mutualism
 When both species benefit from a relationship
 Eg: sea anemones and clownfish
 Describe the relationship:

Clownfish have the same benefit as the shrimp, but also chase
away fish who are able to eat the anemone (because they are
territorial)
Interactions among ecosystems
 All ecosystems are connected, either directly or
indirectly, with other ecosystems
Example of a Direct Ecosystem connection: A pond in
the woods requires water from the forest, shares
organisms with other ecosystems etc…
2. Example of an indirect ecosystem connection: A
nitrogen atom from fertilizer may interact with several
ecosystems and their communities as it goes through
the nitrogen cycle
1.
 Wind, rivers and ocean currents tie the Earth’s
ecosystems together.
Invasive Species
 Also called “Exotic”, “Alien” or “Introduced” Species
 These are species, through human meddling, have
been brought to new habitats
 The consequences can be negative, inconsequential
and even positive (Similar to Symbiosis!).
 Overview:
California Academy of Sciences Video
Ted-Ed Video