Chapters 50-55 Study Guide
written by Henry Yuen

The approach I'm taking to study guides is not to rehash the book or the lecture notes found online for you guys. That's up to you to read. What I'm doing here is outline the Big Concepts (tm) for you so you grasp how everything is linked together, because I think that's where biology is hard - trying to link everything together.

Unifying Theme: Ecology

The point of all these chapters is ecology. Ecology itself is further broken down into these five sections, which correspond to chapters 51-55:

-Population Ecology
-Community Ecology
-Conservation Biology


Ecology is the study of interactions between organisms and the environment. It is both experimental (meaning a lot of work is done experimenting) and descriptional (coming up with theories).

In ecology, the environment consists of:

Abiotic factors - the non-living parts, such as:temperature. light, water, and nutrients.

Biotic factors - the living parts, all the other organisms that are part of the environment.

Interactions is what ecology is all about - how do individuals and species impact the environment they live in? Interactions not only mean interactions between two animals, or two species, but between nonliving factors. So in other words, interactions in an environment occur between both abiotic and biotic factors.

For example:

Pretend we're in Africa, in the savanna, where there's antellopes, gazelles, lions tigers and bears and vultures. Every animal plays a role in the environment, no matter how small or how big. Gazelles eat the grass, lions eat the gazelles, and vultures clean up afterwards. All the interactions together work to form a functional unit. Environments act like one single organism, in a way.

Evolution and Ecology

Ecology and evolution are related to each other. In ecology, interactions drive evolutionary change. Think about it: without anything happening between the abiotic factors or other animals, will there be a need for evolutionary change? That's something to keep in mind.

Important Terms of Ecology

Organismal Ecology - deals with:
behavioral: how the animal behaves in order to live successfully in its environment.
physiological: how the physiology (physiology is the system parts of an organism, like the digestive system, etc) of an animal helps it live successfully in its environment.
morphological: the physical appenditures (arms, legs, eyes, toes, etc) help the animal successfully live in it's environment.

Basically, deals with the organism itself (keyword: individuals)

Populations - the next level higher than organismal ecology, it deals with lots of individuals of the same species, and how they function together to interact with its environment.

Community - The next level higher, it deals with multiple populations, and how they function together to interact with their environment.

Big Concept(tm)

Hopefully you should see some pattern in my bolding, and it should be apparent to you that ecology, again deals with how organisms and organization of organisms deal with the environment.

Abiotic factors: Temperature, sunlight, water, wind, rocks and soil, and disturbances are common abiotic factors that make organisms adapt and use the abiotic factors.

The rest of chapter 50 deal with climate and aquatic and terrestrial biomes. There isn't much there, except some memorizing of all the different terms, there aren't any Big Concepts (tm) there.

Aquatic and Terrestrial Biomes:

Aquatic biomes occupy the largest part of the biosphere (meaning Earth). Ecologists divide aquatic biomes into quite a bit of layers:

General Zones in Aquatic Biomes

Photic Zone (deals with light) - the upper layer where there is enough light for photosynthesis.

Aphotic Zone (deals with light) - the lower layer, where little light penetrates.

Thermocline (deals with temperature) - the layer beneath the mixed layer (remember 9th grade?) where the temperature quickly drops.

benthic zone (benthos at the bottom) - bottom of all aquatic biomes which is made up of sand, organic and inorganic sediments (ooze). Collectively, the organisms that occupy the benthic zone are called benthos. Benthic layer -> Benthos.

Detritus (food) - feeds benthos. In lakes and oceans, detritus filters down from the photic zone.

Freshwater Biomes

Types of freshwater biomes are lakes, ponds, rivers and streams.

littoral zone - well lit waters close to the shore. Rooted and floating aquatic plants thrive here.

limnetic zone - well lit open surface waters farther from the shore.

profundal zone - same as aphotic zone, where dead small organisms sink into. It's like a graveyard or something.

Types of freshwater lakes:

Oligotrophic lakes - deep, not full of nutrients, and the photoplankton in the limnetic zone are not very productive.

Eutrophic lakes - the opposite - are shallow, and the amount of nutrients are very high. So, the photoplankton are usually more productive.

Mesotrophic - somewhere in the middle.

Rivers and streams have different communities than Lakes and Ponds. That's because rivers and streams are dynamic, moving bodies of water while lakes and ponds are still standing. The nutrients in rivers and streams are from the material of the banks they wash off of, so the nutrient contents are different, which supports different communities.

Wetland - area covered with water that supports aquatic plants.

Estuary - where a freshwater stream or river merges with the ocean. It is often bordered by coastal wetlands called mudflats and salt marshes.

Various Aquatic Terms

intertidal zone - where land meets water.

neritic zone - the shallow regions over the continental shelves

oceanic zone - past the continental zone, reaching very great depths.

pelagic zone - open water of any depth

benthic zone - at the bottom of any pelagic zone

coral reefs - aquatic communities that are choked with all types of life forms. Dominanted by coral, filled with numerous species.

oceanic pelagic biome - most of the ocean's water lives here, far away from the shore, which are constantly mixed by ocean currents. Nutrition concentrations here are generally lower.

abyssal zone - deep within benthic communities are the organisms that live in continous, freezing cold. This is called the abyssal zone. Does anybody remember the movie The Abyss? Think it was written by Michael Crichton...no that was Sphere.

Various Terrestrial Biomes

There are about 8 different main terrestrial biomes, and I won't reiterate them here, so just look at them from pgs. 1044-1047.

Various Terrestrial Biome Terms

canopy - the top part of a tree community.

permafrost - Permanently frozen stratum just under the surface of the arctic tundra.

Concepts of Organismal Ecology

Remember, organismal ecology studies how animals meet the challenges of their environment via their behavioral, physiological and morphological abilities.

The success of an organism at survival and reproduction reflects its overall tolerance to the entire set of environmental varibles it confronts. - In other words, the better an organism tolerates the changes in an environment, the better it survives and reproduces.

regulators - organisms need to achieve homeostatis, which is basically stability, so they use regulators, which are mechanisms to help them cope with changes in their environment, like temperature, weather, etc, basically abiotic factors.

conformers - in contrast, conformers change themselves in accordance to the environment.

To get an idea of what regulators and conformers are, think of mammals versus reptiles. Mammals are warm blooded, which means they keep a stable temperature no matter what the environment is like. This means they are regulators - they regulate themselves.

In contrast, reptiles are cold blooded, meaning they rely on the environment to heat them. They are conformers - because they conform to the environment.

Principle of Allocation - this is pretty simple, it says that each organism has limited amount of energy to do it's stuff, like gathering nutrients, surviving predators, etc. The importance of this is that it is related to the distribution of organisms and how they maintain stability (homeostasis). That means in a stable environment, organisms may have extra energy left over for growth and reproduction, because they don't have to expend that much energy adapting to changing environmental factors.

acclimation - substantial but reversible changes that helps an organism adapt to environmental change.




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