Bio - Ch. 51

Explain how and why an El Niño event develops and how it affects global weather patterns.

Normal Pacific Pattern:

• Trade winds blow east → west across the equatorial Pacific.

• These winds push warm surface water toward the western Pacific.

• Along the west coast of South America, surface water is pushed away from the coast.

• This allows cold, deep, nutrient-rich water to rise through upwelling.

• The nutrients support phytoplankton → fish → seabirds and other organisms.

El Niño Pattern:

Equatorial winds weaken/reverse → warm surface water moves eastward → warm water accumulates near South America → cold-water upwelling is suppressed.

The chain is:

Weakened winds
↓
Warm surface water moves east
↓
Peru Current/upwelling is suppressed
↓
Fewer nutrients reach surface waters
↓
Phytoplankton decrease
↓
Fish decrease
↓
Seabirds and other consumers are affected

How does El Nino affect global weather?

It changes the relationship between the ocean and atmosphere

• Asia & Australia → less rainfall

• Central/eastern Pacific → more rainfall

• West coasts of the Americas → more rainfall

• Parts of the northern U.S. → unusually warm winters

• Southern U.S. → unusually cool winters

Summarize the hierarchical levels at which ecologists conduct research.

Level	What is studied?
Organism	An individual organism and its adaptations
Population	Individuals of the same species living together
Community	Multiple populations living/interacting together
Ecosystem	Community + abiotic environment; energy flow & nutrient cycling
Biosphere	All organisms and the places where they live

Organismal Ecology

Looks at how individual organisms respond to their abiotic environment.

Examples:

• physiological adaptations

• behavioral adaptations

• morphological adaptations

• biochemical/genetic adaptations

Population Ecology

Studies populations of the same species.

Questions include:

• How large is the population?

• How does it change over time?

• How does its distribution change?

Community Ecology

Studies multiple populations living together.

Focuses on interactions such as:

• predation

• competition

• environmental disturbance

Ecosystem Ecology

Studies interactions between biotic and abiotic components, especially:

energy flow + nutrient cycling

Biosphere Ecology

The largest scale — the entire biosphere.

Easy progression:

Organism → Population → Community → Ecosystem → Biosphere

Think:

1 individual → 1 species → many species → living + nonliving system → entire Earth

Illustrate how Earth's shape establishes major weather patterns.

A. Earth's spherical shape → differences in solar radiation

Earth is spherical, so sunlight hits different latitudes at different angles.

Equator:

Sunlight hits more directly.

→ travels through less atmosphere
→ concentrated over a smaller area
→ more intense solar radiation

Poles:

Sunlight hits at an oblique angle.

→ travels through more atmosphere
→ spreads over a larger area
→ less intense solar radiation

Therefore:

Equator = warmer
Poles = colder

Illustrate how Earth's tilt establishes major weather patterns.

seasons

As Earth orbits the Sun, this causes different hemispheres to receive different amounts of solar radiation throughout the year.

June:

Northern Hemisphere receives more solar radiation.

→ Northern summer
→ Southern winter

December:

Southern Hemisphere receives more solar radiation.

→ Southern summer
→ Northern winter

Equinoxes:

Sun is directly over the equator.

Important consequence:

Seasonal variation becomes more extreme toward the poles.

• Tropics → relatively little seasonal temperature/day-length variation

• Poles → huge seasonal variation

Illustrate how Earth's rotationestablishes major weather patterns.

Earth rotates on its axis.

Because Earth moves at different speeds at different latitudes, moving air is deflected rather than traveling in a perfectly north-south direction.

This is the Coriolis effect.

It helps create:

• trade winds near the equator

• westerlies/easterlies at higher latitudes

What are the effects of warm/cold air near the equator?

Warm air near the equator:

heats → rises → cools → releases precipitation

Cooler air:

descends → becomes warmer/drier → moves toward other latitudes

This produces three atmospheric circulation cells in each hemisphere.

Why this matters:

These circulation patterns produce predictable global patterns of:

temperature + winds + precipitation

Relate the climate where you live to worldwide, regional, and local geographical features.

🌎 Global factors

• latitude

• solar radiation

• Earth's tilt

• Earth's rotation

• global atmospheric circulation

🌊 Regional factors

Ocean proximity

Oceans moderate temperatures because ocean currents exchange heat with nearby air.

For example, the chapter compares London and Minneapolis. Although Minneapolis is slightly farther south, London has a milder climate because it is influenced by the ocean and the warm North Atlantic Current.

⛰ Local factors

Topography

Mountains affect temperature and precipitation.

As moist air rises over a mountain:

rising air → adiabatic cooling → precipitation

The windward side becomes wet.

Then:

dry air descends on leeward side → warms → absorbs moisture

This creates a rain shadow.

🌡 Microclimate

The immediate environment surrounding an organism can differ from the general regional climate.

Example:

A fallen log can create a microclimate that is:

• cooler

• shadier

• moister

than the surrounding forest floor.

⭐ Big idea:

Global climate patterns + regional geography + local geography = actual climate experienced by organisms.

Formulate a hypothesis about how climate change will influence species distributions and reproductive schedules.

This objective is asking you to make a prediction based on the mechanisms described in the chapter.

Species distributions

As temperatures rise:

• polar species are expected to move toward higher latitudes

• temperate/tropical species may shift toward the poles

• lowland species may move to higher elevations

Reproductive schedules

Warmer temperatures can cause seasonal biological events to occur earlier.

For example:

warmer spring → earlier flowering

and

warmer conditions → earlier migration/reproduction

The chapter reports that, across many species, spring growth and reproduction occurred an average of 2.3 days earlier per decade in the data reviewed by Parmesan and Yohe.

Evidence from Yosemite

Researchers compared modern species distributions with historical data.

They found that some species shifted upward in elevation, while some high-elevation species became restricted to even higher elevations.

A good hypothesis:

If regional temperatures increase, then temperature-sensitive species will shift their distributions toward cooler habitats at higher elevations or latitudes, while seasonal reproductive events will occur earlier.

That's exactly the type of answer this objective is looking for.

Provide evidence that terrestrial biomes are largely a product of global, regional, and local weather regimes.

First: What is a biome?

A biome is a vegetation type plus its associated microorganisms, fungi, and animals.

Main determinant:

Climate is the major determinant of terrestrial biome distribution.

The two most important climatic variables are:

Temperature + precipitation

Evidence #1: Latitude

Temperature and rainfall follow broad latitudinal patterns.

Therefore, terrestrial biomes often appear as bands across Earth's surface.

Evidence #2: Same temperature, different rainfall

Different biomes can have similar temperatures but different precipitation.

For example:

desert vs. grassland vs. savanna vs. tropical forest

can occur at comparable temperatures but differ greatly in rainfall.

Evidence #3: Same rainfall, different temperatures

Other biomes can experience similar moisture conditions but differ in temperature.

Example:

boreal forest vs. temperate deciduous forest

Evidence #4: Local/regional geography

Climate isn't just about global latitude.

• Ocean currents modify temperature.

• Mountains modify precipitation.

• Elevation modifies temperature.

• Local conditions create microclimates.

Therefore, the biome map reflects global + regional + local climate patterns, not just latitude.

Predict which terrestrial biome is likely under given environmental conditions.

This is probably one of the most testable objectives.

You need to be able to look at:

temperature + precipitation + seasonality

and identify the biome.

🌴 Tropical rainforest

Hot + extremely wet

• ≥25°C mean annual temperature

• 
  

250 cm rainfall/year

• rain throughout the year

• high humidity

• extremely productive

• extremely species-rich

• surprisingly nutrient-poor soil

---

🌾 Savanna

Warm + moderate rainfall + long dry season

• ~90–150 cm annual rainfall

• seasonal drought

• grasses + scattered trees

• fire and grazing prevent trees from taking over

---

🏜 Desert

Very low precipitation

• arid

• large daily/seasonal temperature variation

---

🌿 Chaparral

Mild/wet winter + hot/dry summer

• coastal

• dense woody shrubs

• adapted to periodic fire

---

🌾 Temperate grassland

Moderate rainfall + cold winters + warm summers

• relatively dry compared with forests

• deep, rich soil

• drought, fire, and grazing limit trees

---

🍁 Temperate deciduous forest

Moderate temperatures + abundant rainfall

• middle latitudes

• distinct seasons

• trees lose/regrow leaves annually

---

🌲 Boreal forest / taiga

Cold + high latitude

• long, extremely cold winters

• coniferous evergreen trees

• relatively short summer

• generally nutrient-poor soil

---

❄ Tundra

Extremely cold + short growing season

• northernmost biome

• permafrost

• shallow soil

• short vegetation

🧠 Quick biome logic

HOT + WET → Tropical rainforest

HOT + SEASONALLY DRY → Savanna

HOT/VARIABLE + VERY DRY → Desert

MILD WET WINTER + HOT DRY SUMMER → Chaparral

MODERATE RAIN + COLD WINTER/WARM SUMMER → Temperate grassland

MODERATE TEMP + LOTS OF RAIN → Temperate deciduous forest

COLD + HIGH LATITUDE → Boreal forest

VERY COLD + PERMAFROST → Tundra

Design a study that yields data about environmental differences between streams, rivers, and lakes.

First, understand the distinction:

Lotic

Flowing water

→ streams and rivers

Lentic

Standing water

→ lakes

Streams → rivers

Water begins as small flows at high elevations.

headwaters → streams → larger rivers → lake/sea

As water moves downstream:

• flow volume increases

• flow rate generally changes

• substrate changes

• temperature changes

• suspended particles increase

• nutrient sources change

🧪 A study you could design

Question:

How do environmental conditions change from a stream to a river to a lake?

Independent variable:

Type of freshwater environment:

• stream

• river

• lake

Variables to measure:

• water temperature

• flow rate

• depth

• dissolved oxygen

• turbidity

• pH

• nutrient concentration

• light penetration

• suspended particles

Method:

Take multiple water samples from several streams, rivers, and lakes under similar weather conditions.

Measure the same variables at each site.

Then compare the means between environments.

Why multiple sites?

Because one stream and one lake could be unusual.

Multiple samples/sites make your results more representative.

⭐ Important concept:

The chapter emphasizes that physical conditions change along flowing-water systems, while standing-water environments show strong changes with depth and distance from shore.

Compare the neritic, oceanic, and abyssal zones and explain why different organisms occupy them.

This one is easiest if you organize it by depth, light, nutrients, and location.

🌊 Neritic zone

Shallow water over the continental shelf

• relatively shallow

• receives substantial sunlight

• nutrient availability is relatively high

• highly productive

• supports diverse communities

The neritic zone belongs to the pelagic province.

Organisms:

Lots of photosynthetic organisms → lots of food → highly diverse communities.

---

🌊 Oceanic zone

Deep water beyond the continental shelf

It is also part of the pelagic province.

As depth increases:

• light decreases

• photosynthesis becomes limited

• temperatures generally decline

• organisms become increasingly dependent on material produced higher in the water column

In the open ocean, photosynthesis is possible primarily in the uppermost ~50 m, where plankton act as primary producers.

---

🌑 Abyssal zone

Deep ocean bottom sediments

This is part of the benthic province, rather than the pelagic province.

It is:

• extremely deep

• dark

• cold

• high pressure

• lacking photosynthesis

Therefore, organisms cannot depend on sunlight-based primary production locally.

Instead, much of the energy reaching benthic communities comes from falling detritus from above.

Near hydrothermal vents and cold seeps, however, chemosynthetic bacteria can form the base of food webs.

	Neritic	Oceanic	Abyssal
Location	Over continental shelf	Beyond shelf	Deep ocean bottom
Province	Pelagic	Pelagic	Benthic
Light	High	High near surface, low with depth	None
Photosynthesis	High	Mainly upper water	No
Primary producers	Phytoplankton + other photosynthetic organisms	Plankton	Chemosynthetic bacteria in specific environments
Productivity	High	Highest near surface	Generally dependent on sinking material
Typical organisms	Diverse shallow-water communities	Plankton, fish, predators	Benthic organisms, scavengers, predators

The fundamental relationship you need to understand is:

Physical environment → available energy/resources → organisms that can survive there.

Chapter 1 Summary

🧠 THE CHAPTER IN ONE CONCEPT MAP

If you want to understand rather than memorize, Chapter 51 is basically one giant chain:

Earth's physical characteristics
↓
Solar radiation patterns
↓
Atmospheric circulation + ocean currents
↓
Global/regional/local climate
↓
Temperature + precipitation + seasonality
↓
Biome/environment distribution
↓
Abiotic conditions experienced by organisms
↓
Organismal adaptations
↓
Species distributions + reproductive timing

And then climate change disrupts this chain:

Climate change
↓
Temperature + precipitation change
↓
Physical environments change
↓
Species distributions shift
↓
Reproductive schedules shift
↓
Community composition changes

The textbook specifically summarizes this progression: climate governs terrestrial biome distribution, organisms respond to environmental variation, and climate change is already associated with shifts in geographic ranges and reproductive timing.

---

🎯 What I would memorize vs. understand MEMORIZE

• 5 ecological levels

• 23.5° Earth tilt

• Coriolis effect

• 3 atmospheric circulation cells/hemisphere

• major biome characteristics

• lotic vs. lentic

• pelagic vs. benthic

• neritic vs. oceanic vs. abyssal

• photic vs. aphotic

• El Niño → eastward warm water + reduced upwelling

UNDERSTAND

• Why equator is warmer than poles

• Why seasons happen

• Why 30° latitude tends to be dry

• Why mountains create rain shadows

• Why climate determines biome distributions

• Why organisms shift their ranges with climate change

• Why streams change from headwaters → river mouth

• Why marine communities differ with depth/distance from shore

• Why El Niño can affect organisms thousands of miles away

Those "why" questions are where the learning objectives become much more useful than simply rereading the chapter.

If you're studying this for an exam, I would not reread all 28 pages equally. I would use these 9 objectives as your checklist, then make sure you can answer each one without looking at the notes.