Week 4 Part 1 (Ecology Start)

evolution

process by which species change over time through changes in their genetic makeup

• the origins of adaptation and biodiversity

ecology

how organisms interact with each other and their environment

• the nature of adaptation and the limits to biodiversity

levels of biological organization

1. molecules

2. cells

EVOLUTION

3. organisms

4. populations

ECOLOGY

5. communities

6. ecosystems

population

all individuals of the same species in one place at one time

• e.g all the zebras

community

all species living together in one place at one time

• e.g all the zebras, giraffes, elephants, plants, insects

ecosystem

all the species including the non-living environment

• e.g the entire Savannah (including zebras, giraffes, elphants, etc)

ecological questions

3 ecological questions:

• what limits the numbers of species

• what limits the geographic distribution of species

• how do species interact to form communities and ecosystems

CSB

cellular and systems biology asks “how” questions

• how do mitochondria work

• how does cellular respiration work

• how do mitochondrial genomes get encoded?

EEB

ecology and evolutionary biology asks “why” questions

• why do eukaryotic cells have mitochondria

• why do mitochondria have their own genomes

Lynn Margulis

developed the endosymbiotic theory

• proposed life did not take over the globe by combat (competition) but by networking (cooperation, symbiosis, and interdependence)

endosymbiotic theory

endosymbiotic theory of mitochondria

• ancestral eukaryotic cell and ancestral bacterium (mitochondrion) formed a mutually beneficial relationship

  • bacterium provided efficient ATP production

  • host provided protection and nutrients

legumes

legumes like beans, peas, lentils have become widespread due to their symbiotic relationship with nitrogen-fixing bacteria

• legumes form root nodules that house bacteria

• bacteria fix nitrogen (convert nitrogen from air into a form that plants can use like ammonia)

species estimations

there are too many species globally to count

• many (>85%) still unknown to science

• estimated: 8.7 million eukaryotes alone

biodiversity distribution

biodiversity is not equally distributed across the tree of life; to our knowledge…

• bacteria (highest)

• eukaryotes (moderate)

• archaea (lowest)

beetles

beetles take an unusually high percentage on the tree of life

• old view: the Creator must have a fondness for beetles

species interactions

the ways different species affect each other in an ecosystem

• influence survival, reproduction, and population dynamics

range

a species distribution (where it lives on Earth)

determining where species live

to determine where a species lives we can:

• survey them

• collect them

eBird

a global online platform where everyday people (citizen scientists) can record and share bird observations (species, numbers, locations, dates)

• collects massive amounts of data on bird biodiversity

range factors

factors determining where a species lives includes

• dispersal ability

• abiotic conditions

• species interactions

there are gradients of conditions and we expect organisms to perform best at certain points along the gradient

dispersal ability

a species must be able to reach a location to live there.

• barriers like mountains, oceans, or human structures can limit range

abiotic conditions

not made of living things—the physical environment

• climate, nutrients, sunlight, elevation

species interactions

made of living things—other species interactions

• competition, predation, mutualism

temp range in species

the Great Inca Finch has highest density at ~10ºC while the Scarlet Macaw has highest density at ~25ºC

range of tolerance

species have ranges of tolerance along environmental gradients

• certain tolerance zones affect reproduction, growth, survival

• beyond survival, zones become lethal

Thomas Malthus

highlighted that abundance is not unlimited — it’s constrained by environmental limits

abundance

species can be abundant or rare at different spatial scales

• a locally abundant species may be globally rare

temporal scale

the distribution and abundance of species is not static

• over millions of years

  • most life is dead

• over 100 years

  • ecological succession: how a community changes following disturbance

  • shifts in population sizes and ranges due to human activities

• within one or a few years

  • seasonal changes in abundance or range (e.g migration)

  • population growth and decline

species at risk of extinction

32% of known vertebrates are dec in pop size or range

• among 177 well-studied mammal species, all are declining

  • more than 40% have lost over 80% their original range

ecological niche

a species ‘role’ in its environment

• combination of physiological tolerances and resource requirements for the species

the Hutchinsonian niche

a model where each axis is an ecological factor important to the species being considered; includes

• fundamental niches (full range of conditions where species could survive

• realized niches (actual space the species occupies in nature)

Hutchinsonian niche example

a frog may be able to live in temperatures between 10-30°C and eat insects 0.5-2 cm long (fundamental niche)

but if snakes compete for the same prey and/or predators are present, the frog may only survive in a more limited range, say 15-25°C and 1-1.5 cm prey (realized niche)

climatic variables

climate can be an important ecological factor to consider

• Scarlet Macaws can live between 10-28°C but often inhabit areas with temp ~25°C

weather

the day to day variation in environmental variables including temperature, precipitation, wind, cloud coverage

climate

the long term average weather

climate factors

climate varies across the globe and ultimately determines biomes

• seasonality a function of temperature and rainfall

• temperature mostly a function of latitude

• rainfall mostly a function of atmospheric circulation

higher latitudes

result in colder temperatures

latitudinal variation

because the Earth is spherical, sunlight hits different latitudes at different angles

• at the equator, sunlight hits directly (more vertically)

  • rays spread over a smaller area

• at higher latitudes, sunlight hits at an angle

  • rays spread over a larger surface area

light energy and latitude

light energy varies by latitude

• at the equator (low latitude)

  • sunlight is more intense per unit area

• at higher latitudes (closer to the poles)

  • the same amount of sunlight is spread over more surface (less energy per unit area)

sunlight energy equation

how energy density changes with latitude

• because Earth curves away from direct sunlight at higher latitudes, the energy per area squared drops

energy / area²

seasons and sunlight

there is seasonal variation in amount of sunlight. this happens because

• the Earth is tilted 23.5°C

• Earth orbits the sun once per year

the effect of Earth’s tilt

March 20 (Spring Equinox)

• neither hemisphere tilted toward sun

• days begin getting longer, temp gradually increases

June 22 (Summer Solstice)

• northern hemisphere tilted toward sun

• days are longer, temp increased

Sept 22 (Fall Equinox)

• neither hemisphere tilted toward sun

• days begin to shorten, temp gradually decreases

December 21 (Winter Solstice)

• northern hemisphere tilted away from sun

• days are shorter, temp decreased

direct rays

sunlight that hits the Earth at a 90° angle (straight overhead)

• these rays are the strongest and most intense

• only places near the equator (b/w 23.5 N, Tropic of Cancer, and 23.5 S, Tropic of Capricorn) ever receive direct rays

  • equator is only hit during the equinoxes (e.g. March and Sept)

Hadley cells

large-scale atmospheric circulation patterns that occur near the equator

• makes equatorial regions rainy

Hadley cell steps

1. heated air rises, air cools as it rises (5-10°C/km)

2. as air cools, water vapour condenses and falls as rain near the equator

3. air warms again as it falls

*dry, high-pressure areas at ± 30 degrees latitude

atmospheric cells

atmospheric cells including Hadley cells interlock like a gear train

• e.g. movement of air in the Hadley cell affects the Ferrell cell next to it

areas where air rises are wet

• when warm, moist air rises, it cools and the water vapour condenses

areas where air sinks are dry

• when air sinks, it warms and dries out (because sinking air compresses and heats, reducing relative humidity)

intertropical convergence zone

an area where Hadley cells from both hemispheres converge at the equator

• where warm, moist air rises because the intense sunlight heats the surface at the equator

• the rising air cools and condenses causing frequent thunderstorms and heavy rainfall

• ITCZ is responsible for much of the tropical rainforest climate (e.g. the Amazon and Congo basins)

ITZ and tracking direct rays

the ITZ and Hadley cells track the direct rays of the sun

• when it’s summer, the ITCZ moves north (closer to the Tropic of Cancer)

• when it’s winter, the ICTZ moves south (closer to the Tropic of Capricorn)

ITZ wobbly lines

the ITZ is not a straight line, it is wobbly

1. land heats up faster than the ocean, so over continents, the air rises more strongly

• causes the ITZ to bulge toward the hemisphere with more solar heating

Coriolis Force

Earth spins faster near the poles than at the equator

• shapes the direction of the major ocean currents and the Trade Winds

Coriolis Force example

if you threw a packet of air towards the north pole, it would appear to curve eastward

• air travelling faster at higher latitude eastward

if you threw a packet of air towards the equator, it would appear to curve westward

• air travelling slower at lower latitude eastward

wind patterns

are the result coupled cells plus the Coriolis effect

the roaring forties

a band of westerly flowing winds at around 40°S

• not much land mass

• very windy and wavy

wandering albatross

can fly up to 6000 km in 12 days

• adapted to reduce energy cost of foraging by using dynamic soaring

dynamic soaring

wandering albatross fly up to catch the wind and glides back down close to sea to gain speed

energy expenditure

wandering albatross expend only a little more energy flying than resting on land

terrestrial vegetation

general trends of terrestrial vegetation with climatic variables

• environmental gradient defined by temperature and precipitation

latitude and biomes

latitude determines terrestrial biomes because

• temperature and rainfall tend to be affected by latitude which in turn affect biomes

deserts

deserts exist around 30° N and S

equatorial rainforests

equatorial rainforests exist around 0°

climate patchiness

Earth has broad climate zones arranged by latitude (belts) but within them, there are patches of different climates caused by local geography and conditions

1. thermal inertia

2. precipitation

thermal inertia

oceans heat up and cool down slower than land, moderating nearby land air temperatures

• without oceans nearby as buffer, temperatures on continental land masses change rapidly (very cold winters, very hot summers)

precipitation

ocean currents affect precipitation

• warm ocean currents → warm air above them → warm air holds more moisture (cold air less) → more evaporation → more precipitation

• driest deserts occur inland of cold-water upwellings (cold water cools air above it, cool air can’t hold much moisture)

orographic precipitation

precipitation caused when moist air is forced to rise over mountains

• as the air rises, it cools and because cool air holds less moisture → water vapour condenses into clouds → precipitation happens

niche limits

• the niche of an animal means the full range of environmental conditions (like temperature, food, habitat) where it can survive and reproduce.

• these are the fundamental limits based on what the animal needs or can tolerate biologically

geographic range limits

• the geographic range is the actual area on Earth where the animal is found.

• sometimes this matches the niche perfectly, but often it doesn’t

geographic ranges and biomes

• animals' geographic ranges often line up with biomes (like deserts, forests, tundra) because those biomes match their niche requirements (climate, vegetation).

• but sometimes, the geographic range doesn’t match biome boundaries:

  • transcend biomes

  • recent history

  • limited by other organisms

transcend biomes

some animals can live in many different environments — they’re super flexible (generalists) and can cross biome boundaries easily

recent history

an animal might potentially live farther, but hasn’t reached those places yet because it hasn’t dispersed or migrated there.

• so, the geographic range is smaller than the niche would allow

limited by other organisms

sometimes animals could survive in a place based on climate, but other species affect them:

• predators or competitors may exclude them.

• or some animals need other species (mutualists) to survive, limiting where they can live.

ecological niche modelling

computer-based method that predicts where a species could live based on where it currently lives and environmental factors

ecological niche modelling uses

Why is it useful?

• Predict biological invasions: Where might an invasive species spread in a new region?

• Forecast range shifts due to climate change: How might species’ ranges move as temperature and rainfall patterns change?

• Track spread of vector-borne diseases: Predict where disease-carrying species (like mosquitoes) could live and spread diseases.

ecological niche modelling data

primarily uses climate data to make predictions

• sometimes on other niche factors like food availability or habitat, but that’s less common because climate data is easier to get

predicted range shift

climate change will influence malaria distribution in South America

• malaria is vectored by Anopheles mosquitoes

  • as climate gets warmer, the range of Anopheles mosquitoes will inc (covering 46% of SA by 2070 compared to 25% in 2015)

observed range shifts

though many factors influence a species’ possible range, there is considerable evidence that species are moving polewards—in line with recent changes in climate

• 2003 study found that 1045 species are moving polewards at a rate of 6.1 km per decade

• 2011 study found that 1367 species are moving polewards even faster at a rate of 16.9 km per decade