Unit 5: Ecology Bio II Final

What is ecology?

the study of interactions between
living organisms and their environment

Levels of ecology

Organismal
• Individual organisms
Population
• Members of the same species living in the same area at the same time
Community
• All species living in the same area at the same
time
Ecosystems
• Includes all biotic and abiotic components of an
area organism

Biogeography

the study of the distribution of organisms and the abiotic factors that determine those distributions

Species distribution

• Which species live in which areas and why

• Determined by biotic and abiotic factors

Endemic species

species that are found only in a specific geographic range

Generalist species

species that are found in many geographic ranges

Abiotic Factors

Energy Sources, Temperature, Water, Inorganic nutrients and soil, Oxygen, Wind, Fire, 

Terrestrial Biomes

Determining factors are temperature, sunlight and precipitation (seasonality)

Tropical wet forset biome

• Temperature and sunlight are stable year round

• Plants have year-round growth

• Significant precipitation

• highest animal and plant diversity

Savannah

• Hot temp

• minimal precipitation

• Fire is important abiotic factor

Subtropical Desert

• Intense temperature swings

• Precipitation is basically negligable

Chaparral

• Significant daily temperature swings

• Precipitation: Winter rainfall , dry summers

Temperate
Grasslands

Seasonal temperature fluctuation
• Warm summers and cold winters

Precipitation: Annual, periodic rainfall, only winter is dry

fire is an important regulator

Temperate Forest

Seasonal temperature fluctuation
• Warm summers and cold winters

Predictable annual rainfall, it is constant

Deciduous trees

Soil rich in inorganic and organic material

Boreal Forest

Low annual temperature
• Cool, wet summers
• Cold, dry winters

Predictable annual precipitation, mostly snow not rain

conifer trees

Lower species diversity than temperate forest

Artic Tundra

Very low annual temperature

Extreme sunlight conditions
• 24 hours in summer, 0 hours in winter

Extremely low annual precipitation, mostly snow

Permafrost soil

Low species diversity

Aquatic Biomes

Water itself is the medium in which organisms live
• Different physical and chemical properties than air

Ocean

Categorized by zones based on light penetration (photic, aphotic,
abyssal)

Intertidal zone is area between low tide and high tide

Neritic zone extends from intertidal zone to depth of 200 meters
• Photosynthesis occurs

Oceanic zone is open ocean

Benthic zone is at the bottom of all zones
• Nutrient rich due to detritus that falls to ocean floor
• Very cold, high pressure, high oxygen, low nutrient

Coral Reefs

Symbiotic relationship between coral polyps (cnidarians) and algae

Located in the photic (light) zone and warm waters

Coral organisms secrete calcium carbonate that forms the reefs

Coral reefs support great diversity of invertebrates and vertebrates

Acidification of the water by carbon dioxide and climate change threatens coral reefs

Estuaries

Where ocean and freshwater meet

Brackish water

nurseries for many species of fish and
invertebrates

Salinity varies considerably

Nutrient rich

Biomass is high but biodiversity is low

Freshwater: Ponds and lakes

Great variety in size of lakes and ponds

Lentic water (not flowing)

Temperature is most important abiotic factor
• Thermal stratification in summer
• Warmer water at top and cooler water at bottom
• Reverses in winter

Light penetrance determines photosynthetic organisms
• Base of food chain
• Deeper light penetrance, more photosynthetic organisms

Nitrogen and phosphorous are limiting factors
• Determining factor for phytoplankton

Run-off from farms, yards, etc. lead to eutrophication of lakes
• Increased algae growth
• Blocks light penetrance
• Consumes majority of dissolved oxygen
• Lake/pond is polluted

Freshwater: River and Streams

Great variety in size of rivers and streams
• Lotic water (flowing)
• Carry water from headwaters (source) to lake or ocean

Rate of flow is an important abiotic factor

Slower flow brings more debris and plakton and warmer temp

Wetlands

Soil is permanently or periodically saturated with water

Vegetation is rooted in the soil but extends above surface of
water across entire surface area

Wetlands have hydrophytic vegetation and hydric soil

Marshes, swamps, bogs, mudflats, and salt marshes

population

a group of individuals of the same species
living in the same area at the same time

Size versus density

• Population size (N) = total number of individuals
• Population density (Dp) = # of individuals within a specific area

How to sample populations

Quadrat used for immobile organisms such as plants
• Square area (typically 1 m2)
• Multiple quadrats placed randomly within habitat
• Count number of individuals within quadrat

Mark and Recapture used for mobile organisms such as
animals
• Capture animal, apply marking (band, tag, paint, wing clips)
• Release back into habitat
• At later time, capture animals again. Will get mix of marked
and unmarked animals
• Ratio of marked to unmarked help determine density

Types of dispersion

How individuals are distributed throughout the habitat

• Uniform dispersion

Individuals are equally spaced
• Random dispersion

Individuals are distributed randomly with no pattern
• Clumped dispersion

Individuals are clustered in groups

Survivorship curves
what are the differences between the three curves, what type of reproduction, what type of animals

Type I curve:
• Low death rate in early and middle
years
• Higher death rate in older
individuals
• Found in species that produce low
number of offspring/parent and
provide high amount of parental
care
• Elephants, Apes

Type II

Mortality rate increases
consistently as animal ages
• Found in species that produce
“normal” number (approximately 3-
10) offspring/parent and provide
significant but brief amount of
parental care
• Birds, rodents

Type III

Very high death rate in early life
• Death rate declines as individuals
age
• Found in species that produce
many offspring/parent and provide
little or no parental care
• Plants, fish, insects

Life Histories:
Early versus late reproduction

Early Reproduction
• Individual reproduces at early age
• Produces more offspring but, at expense of self growth and
maintenance
• Often do not live very long

Late Reproduction
• Individual reproduces later in life
• Produces fewer offspring
• Provides greater parental care
• Both contribute to high survival rate of offspring
• But, individual may not live long enough to reproduce

Both are examples of energy trade-off strategies

Life Histories:
Semelparity versus iteroparity

Individuals reproduce only once in their lifetime
• Use most of energy budget on reproduction, die as a result
• Produce many offspring, little or no parental care
• Low survivorship of offspring
• Annual plants, salmon

Individuals reproduce repeatedly during their lifetime
• Typically reproduce once per year
• Produce few offspring, provide parental care
• High survivorship of offspring
• Budget energy for maintenance of life and reproduction
• Birds, wolves, lions

Life Histories:
Fecundity

the potential reproductive capacity of an individual or population, representing the maximum number of offspring an organism could produce over its lifetime

Population Growth Models:
Exponential versus Logistic

Exponential Growth
• Population growth with unlimited natural
resources
• J-shaped growth curve
• Population (N) plotted over time
• Exponential growth only possible with
infinite resources
• Not realistic for most organisms
• Competition is real!
• Most successful will survive to pass on their
traits to offspring

Logistic Growth
• Population growth with limited natural resources
• Growth slows as population reaches
environmental carrying capacity (K).
• Maximum population size supported by environment
• S-shaped curve
• Initial exponential growth
• Greatest when population is at ½ carrying capacity
• Then growth slows as resources become limited
• Finally, growth levels off at carrying capacity
• Assumes all individuals have equal access to
resources
• Equal chance for survival
• Not realistic!
• Genetic variation means that some individuals
are better adapted to environment

K-selection versus r-selection

Carrying capacity is regulated by:
• Density-Dependent factors
• K-selection
• Density-Independent factors
• r-selection

K-selection

Greater density = greater mortality

Reproduction:
• Few, large offspring
• Greater survival rate of each offspring
• Long gestation period
• Long-term parental care

r-selection

Greater density does not necessarily mean
greater mortality

Reproduction:
• Many, small offspring
• Lower survival rate of individual offspring
• Offspring grow/mature rapidly
• No long-term parental care or no parental care at all

What is a community?

includes all populations (all species) living in the same area at the same time

Species Richness:

The number of different species in the community

Species Evenness/Diversity:

# of species
occupying the same habitat and their relative
abundance
• How many different species are present, which
species are present, and the abundance of
individuals of each species are important

Species richness + species evenness

= species diversity

What is community ecology?

studies the interactions
between those different species

How are interactions defined?

Interactions are defined by whether they harm,
help or have no effect on the species involved.

Predation

Good for the predatory, bad for the prey

Prey animals evolve mechanisms to
escape predation
• Mechanical
• Chemical
• Physical
• Behavioral

Aposematic Coloration: Animals &
plants using chemical defense often
use bright coloration as a warning to
predators

Cryptic Coloration: Animals blend in
with their environment

Types of mimicry:

Batesian mimicry: harmLESS species
look like species that are harmFUL

Mullerian mimicry: Multiple species
exhibiting the same type of defense all
have same coloration

Herbivory

Good for the herbivore, bad for the plant

Plants develop defenses to herbivores
• Mechanical: thorns
• Chemical: toxins

Parasitism

One species benefits and the other is harmed by the interaction

Competitive Exclusion

Two or more species cannot occupy the same niche at the same time

Leads to Resource Partitioning
• Differentiation allows two or more species to
co-exist
• Use different part of the habitat
• Feeds at different time of day

Types of symbiotic relationships

Commensalism: One species
benefits from the interaction, the
other species is not helped nor
harmed

Mutualism: Both species benefit
from the interaction

Parasitism: One species benefits
and the other is harmed by the
interaction

Community Structure

Keystone species: a species
whose presence is key to
maintaining biodiversity in an
ecosystem
• Gopher Tortoise

Invasive species: a
nonnative species that
threatens the balance of the
ecosystem they are
introduced to
• Feral Hogs and Burmese Pythons
in Everglades

Ecosystem Ecology

the study of interactions between living
organisms and their environment

Disturbance

In response to disturbance, ecologists measure
• Resistance: the ecosystem’s ability to remain in equilibrium despite disturbance
• Resilience: the ecosystem’s speed of recovery after a disturbance

Food chains

A Food Chain is a linear sequence of energy
movement through organisms

Primary producers (plants) —>primary consumers (herbivores)  —>
secondary consumers (carnivores) —> tertiary (apex) consumers (eat carnivores)

Food webs

A Food Web accounts for all interactions between different species within the ecosystem

Ecosystem Modeling

A Holistic Ecosystem Model quantifies the competition, interactions and dynamics of an ecosystem

Best type of study but expensive and time-consuming
• Unethical to alter an ecosystem just to study it

Mesocosm Model
• Partitions off part of ecosystem

Pro: In-situ (in place) study
• Con: partitioning organisms changes the dynamics

Microcosm Model
• Recreates ecosystem
• Pro: ease of study
• Con: removing organisms changes the dynamics

Trophic Levels

Ecosystem productivity is the percent of energy
entering the ecosystem as biomass at each trophic
level
• Biomass is the measurement of living and previously living
organisms within a trophic level

Energy flow through levels

Biogeochemical Cycles

Chemicals that make up living organisms cycle
through ecosystem
• Carbon (found in all organic molecules)
• Oxygen (found in water and organic molecules)
• Hydrogen (found in water and organic molecules)
• Nitrogen (found in proteins and nucleic acids)
• Phosphorous (found in nucleic acids)
• Sulfur (found in proteins)

play a role in nutrient recycling
between biotic and abiotic components

carbon cycle: the process where carbon atoms move between the atmosphere, oceans, land, and living organisms, primarily through photosynthesis, respiration, decomposition, and geologic processes like the formation of fossil fuels

Hydrologic cycle: continuous movement of water on, above, and below the Earth's surface, involving processes like evaporation, transpiration, condensation, precipitation, and runoff

Biological Magnification

the increasing concentration of toxic substances in organisms at successively higher levels of a food chain

Human Impact

Burning fossil fuel exponentially speeds up the amount of carbon entering the atmosphere

Humans raise large number of animals for consumption
• Those animals contribute to increased methane entering the
atmosphere

These anthropogenic sources of carbon are leading to climate change!

Biodiversity

a measurement of the number/abundance of species present in a given area

Types of Biodiversity

Species biodiversity
• The number of species, along with their abundance, in a given area

Genetic biodiversity
• Genetic variation present in the individuals in a population or species

Ecosystem biodiversity
• Number of different ecosystems in a given area

Patterns of Biodiversity

Biodiversity is not evenly distributed on Earth

Biomes near the equator have greater biodiversity than biomes in the far north or far south

Five Mass Extinctions

Ordovician-Silurian:

• Life was almost exclusively in oceans
  • Caused by glaciation followed by extreme warming

Devonian:

• Affected marine species, not terrestrial

• Cause not understood

Permian:

• Largest extinction event on Earth

• Dramatically altered the course of evolution on Earth

Triassic-Jurassic:

• 85% of species extinct

• Cause unknown but occurred right before Pangaea broke apart

Cretaceous:

• All dinosaurs extinct except theropod clade

• Caused by asteroid impact off Yucatan Peninsula and volcanic activity

• Mammals became dominant species following this extinction

Holocene

Anthropogenic Extinctions

Coincides with expansion of European colonies around the
world

ex: Dodo bird (1662), Stellar’s sea cow (1778), Passenger pigeon (1914), Carolina parakeet (1918), Japanese sea lion (1950), Caribbean monk seal (1952)

Extinction rate is increasing exponentially

Measuring Biodiversity

We need one global database for all described and named species
• All known and new species need to be entered into database

DNA Barcoding
• Sequences area of rapidly evolving genome
• Eukaryotes, use mitochondrial DNA
• Plants, use chloroplast DNA
• Fungus, use internal transcribed spacers in RNA

Conservation: National and International Agencies

International Union for Conservation of Nature (IUCN):

Classifies species as critically endangered, endangered or
vulnerable

Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES):

Prevents capture and transporting of 33,000 species

US Endangered Species Act (ESA):

Protects species that are listed as critically endangered or
endangered

North American Migratory Bird Treaty Act (MBTA):

protects 800 species of birds
• Illegal to kill, disturb, and transport birds or parts of birds

Conservation: Preserves

Create wildlife and ecosystem preserves
• Area of land protected from development

Size and quality are important

Connectivity to other preserves is paramount for gene flow

Large, high quality, interconnected preserves work best
• Expensive to purchase
• Developers want quality land
• Politics plays a role

Conservation: Habitat Restoration

Restoring dead or damaged ecosystems improves the
ecosystem for all organisms within it

Need to identify keystone species in all ecosystems
• Protect them

Conservation: Captive breeding

Zoos and aquariums help conservation efforts with captive breeding programs
• Animals (or their semen) are transferred between zoos to increase genetic diversity
• Genetic specialists manage global breeding programs