Ecology

ecology

the scientific study of the interactions between organisms and their environment

What are the two components of environments?

abiotic (non-living) and biotic (living)

Abiotic environment

chemical and physical factors

ex. temp, light, water, wind, pH

affect the ability of individuals to survive and reproduce

individuals differ in their “tolerance”

biotic environment

living component of environment

can have dramatic influence on species survival and reproduction, and on abiotic environment

reciprocal selection

a process where two entities exert selective pressures on each other, causing concurrent evolutionary changes

evolutionary arms race

Scales of ecological organization

organism → population → community → ecosystem → biosphere

What physical factors drive the distribution of organisms at the global scale?

climate

1. light

2. temperature

3. precipitation

What three factors drive global climate?

• sunlight, particularly to the tropics

• movement of the planet

• atmospheric and ocean circulation

What causes seasonality?

the tilt and movement of the earth

Why is sunlight more intense at tropical latitudes?

At the equator, sunlight hits the earth at a steeper angle, which allows it to travel through less atmosphere and less energy is reflected back.

Why does air move upward at the equator? What process does this phenomenon create?

• As the sun beats down on the tropics, the molecules move faster, and the heated air expands, becoming less dense and rising

• Creates the Intertropical Convergence Zone (ITCZ)

Intertropical Convergence Zone (ITCZ)

The region that circles the Earth, near the equator, where the trade winds of the Northern and Southern Hemispheres come together, causing air to rise, cool, and create intense thunderstorms and heavy rainfall.

Hadley cells

massive, thermally driven atmospheric circulation patterns in the tropics, operating between 0 and 30 degrees north/south of the equator

What effects do latitudinal patterns of atmospheric circulation have on climate patterns?

They transfer an immense amount of heat energy from the hot tropics to the cold poles. Without this transfer, the poles would sink towards absolute zero in winter, and the equator would reach fantastically high temperatures throughout the year.

Coriolis Force

The apparent curving of moving objects - like wind and ocean currents - caused by Earth’s rotation. Paths curve to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Why do trade winds form?

Because the earth is spherical and blow from East to West

Drivers of water movement

• gradients in heat and salinity

• winds

Global climate is modified to produce regional climate by:

1. landmasses (heat faster than oceans)

   1. monsoons

   2. land-sea breeze

2. mountain ranges

   1. deflect winds

   2. produce rain gradients

3. ocean

   1. moderates temperature and rainfall

microclimate

a local zone where the climate differs from the surrounding area

What’s the difference between climate and weather?

weather is the day-to-day state of the atmosphere, and its short-term variation in minutes to weeks.

climate is how the atmosphere behaves over a relatively long period of time.

What pattern have ecologists noticed about species turnover since the 70s? What does this signal?

Species turnover has slowed by 1/3 since the 70s. This may signal biodiversity loss.

What is the main driver of climate change?

The rise of greenhouse gases

greenhouse gas

a gas that absorbs and emits infrared (heat) radiation, but not radiation in or near the visible spectrum

What are the main greenhouse gases?

• water

• CO2

• methane

• N2O (nitrous oxide)

• O3 (ozone)

• CFCs (chlorofluorocarbons)

Impacts and feedbacks of the greenhouse gas effect

• increase in extreme weather events

• 1/3 summer sea ice in Arctic is gone

  • influences earth’s “albedo”

  • starving polar bears

• oceans are 30% more acidic

  • affects organisms w/ calcified shells

• atmosphere over ocean is 5% wetter

• warmer ocean causing massive coral bleaching

Main drivers of global climate

• the sun

• planet movement

• circulation

biome

• a distinct physical environment inhabited by ecologically similar organisms w/ similar adaptations

• biomes are typically characterized by dominant type of vegetation

convergent evolution

when unrelated organisms evolve similar traits or behaviors

What determines a biome?

physical environment

• soils (or substrate)

• disturbance (natural or human-induced)

climate and climatic variability

• temperature

• precipitation

• seasonality

How do you read a walter climate diagram?

• ecosystem is water-limited if temp line (red) exceeds precipitation line (blue)

• N. hemisphere x-axis starts in January, S. hemisphere x-axis starts in July

• White zone denotes frozen conditions, inhospitable for life

• effective growing season (temp above 0 C) is highlighted on x-axis

Tropical rainforest

• found within 20 degrees latitude from the equator

• average annual temperatures exceed 20 C and total annual rainfall exceeds 250 cm

• most species of any terrestrial biome

• soils cannot usually support long-term agriculture because warm, wet conditions speed the decomposition of detritus and the reabsorption of released nutrients by plants

Desert

• can be hot or cold, precipitation low and sporadic

• plants are thorny and adapted to conserve water (fleshy stems and leaves)

• plants have thick cuticle and open stomata only at night

• no big mammals because there’s no shade and they need water

• dominant mammals are typically burrowers

Tropical seasonal forest/savanna

• found between 10-23 degrees of from equator in regions where average temps exceed 20 C and total annual rainfall is between 80-250 cm, with a pronounced dry reason

• dominated by smaller-statured tree species than in tropical rain forests, many of which are deciduous during dry season

• dense understory

• as dry season advances, vegetation decreases in stature, frequency of succulents increases, and leaves are more frequently protected by thorns