Ch. 3 Ecology: basic needs of living things

Transcript Ch. 3 Ecology: basic needs of living things

CHAPTER 3

Basic Needs of Living Things

Introduction to ecology

• • •

Ecology is

the study of Interactions between living things and the environment And the distribution and abundance of organisms • • Understanding ecological terms and concepts helps us see how environmental changes affect living things Ecology is a hierarchy of studies • Scientists operate at different scales and ask different questions © 2011 Pearson Education, Inc.

Organisms in their environment

• The next slide shows you an example of the heirarchy of life —how one organism (in this case, a panda) fits into the whole scheme of its ecosystem. • From that slide, you should get the idea nature is complex; it is, essentially, layer upon layer of organisms and their interactions with their surroundings (a.k.a., their habitat). See next slide… • So, why are pandas an endangered species?

The hierarchy of life

• •

Species within a biotic community

Species in a community depend on each other • Typically, plants support animals in a community.

• Populations of different species within a biotic community constantly interact with each other and with the abiotic environment (i.e., water, air, rocks).

It is hard to define a species, but in general: A species has members that can interbreed and produce fertile offspring. So, the panda is a species. And so is the bamboo that it eats.

• •

Populations and biotic communities

Population

: a number of individuals

of the same species

that make up an interbreeding group. • It refers only to individuals of a species in one area • For example, gray wolves in Yellowstone National Park OR Asian tiger mosquitoes in Carteret County.

• A species would include all gray wolves in the world.

community (biotic community):

includes all of the populations that exist in one area. • Includes plants and animals

as well as things you can’t always see, like microscopic organisms

Predict the “community” here:

Is the community the same in winter?

•

Okay, so what are Ecosystems?

Ecosystem

= community

+ abiotic factors

such as air, water, rocks, pH, and other non-living factors.

• Examples of ecosystems you know and love: pine forest, salt marsh, coastal ocean, coral reef, sand dune, desert, pond, lake, river, pocosin (what’s that?) • Humans are part of ecosystems, too! • Ecosystems lack distinct boundaries • Species can occupy multiple ecosystems and migrate between them. Monarchs migrate from Mexico to N.A.

STRESS

—yes, it affects us all!

• • Different species thrive under different conditions.

For every factor there is an

optimum

• A certain level where organisms grow or survive best • They generally do not survive at extremes • • • •

The next slide shows you the range of temperature tolerance for bamboo.

What is the optimal temperature range for bamboo?

What is its range of temperature tolerance?

How do warmer temperatures affect its growth rate?

Survival curve

•

A fundamental biological principle:

Every species has an optimum range, zones of stress, and limits of tolerance for every abiotic factor (and of course, tolerance limits for biotic factors too) • The “sum” of tolerances for a variety of such environmental factors (not just temperature, but also humidity, rainfall, pH, sun intensity, wind, etc.) affects an organism’s growth, health, survival, and reproduction —

and thus influences the vulnerability of a species to extinction.

That will become clearer when we discuss endangered species later on.

• • •

Habitat and niche

Habitat

: the place —defined by the plant community and physical environment —where a species is adapted to live • • It can be large, like a deciduous forest, swamp, etc.

or small (microhabitat

): puddles, rocks, holes in tree trunks

Niche

: the sum of all conditions and resources under which a species can live. I like to think of “niche” as an organism’s JOB within its ecosystem: • For a panda, its niche would include eating bamboo!

Resource partitioning

•

Producers make organic molecules

Producers —you know them as plants—

are able to make organic molecules (FOOD) from raw materials (like CO 2 , H 2 O, N, P) using chlorophyll.

• • Green plants use the process of photosynthesis to make sugar by taking in carbon dioxide, water, and light energy —and releasing oxygen as a by-product (Thank Goodness for that by-product!) Plants are not the only producers —algae and certain special bacteria are huge contributors, too.

Producers as chemical factories

Consumers consume producers!

•

Consumers:

organisms that live on the production of others; consumers derive their energy from feeding on and breaking down the organic matter made by producers • They may do this directly (horse eats hay) or indirectly (hawk eats rabbit that ate plants).

• Where does carbon dioxide fit into this process?

A consumer uses O2 and releases CO2

Cellular respiration is not 100% efficient

• •

One-way flow of energy

Most solar energy entering ecosystems is absorbed • • Heats the atmosphere, oceans, and land Of all the solar energy that hits the Earth, only 2 –5% is passed through plants to consumers Excess energy from the sun —what happens to that? • • Is eventually re-radiated into space Carbon dioxide and certain other molecules in our atmosphere trap some heat next to the Earth; this allows Earth to be habitable. •

But what happens when too much carbon dioxide is released into the air?

• •

The cycling of matter in ecosystems

Matter moves

in circular pathways of elements involving biological, geological, and chemical processes The carbon cycle

(this is a biggie —learn this one!)

• • Start with the CO 2 reservoir in the air Becomes organic molecules via photosynthesis • Carbon is naturally respired by plants and animals (think about exhaling carbon dioxide (CO 2 )) • In oceans, photosynthesis moves CO 2 from seawater into algae and then into fish, clams, etc.

The global carbon cycle

Some processes are significant in transferring carbon

• Combustion of fossil fuels releases CO 2 to the air • • Fossil fuels —coal, oil, and natural gas—were formed millions of years ago, when carbon was locked into the organic material we call crude oil, for example. • Over the past 100 years, we have burned about half of the Earth’s crude oil.

Relatively speaking, that is a very sudden release of a lot of carbon dioxide

What about the ocean? It is absorbing a lot of the carbon dioxide. This is not a good thing.

• • • •

Human impacts on the carbon cycle

Human intrusion into this cycle is significant Burning fossil fuels has increased atmospheric CO 2 by 35% over a century or so.

Meanwhile, we are also diverting or removing 40% of the photosynthetic effect of land plants (by clearing forests, especially rainforests).

Deforestation and soil degradation release even more CO 2 • as burning or decay occurs.

• •

The phosphorus cycle

Phosphate is essential to life! (it’s in ATP and DNA) Phosphate originates in rock and soil minerals • Excessive phosphorus can stimulate algal growth • Excess phosphorus can come from erosion of land; when rock breaks down, phosphate is released •

Phosphate can become

Human impacts on phosphorus cycle

• • • • The most serious impact comes from fertilizers Phosphorus is mined and made into fertilizers, animal feeds, detergents, etc.

When added to soil, it can stimulate production • Human applications have tripled the amount of P reaching the oceans, accelerating the cycle Excess phosphorus in water (runoff from fields and lawns and erosion) leads to severe pollution • Can cause algae blooms and subsequent fish kills from rapid decomposition and anoxia (hypoxia) © 2011 Pearson Education, Inc.

The nitrogen cycle

• Air is the main reservoir of nitrogen (N), as N 2 • Nitrogen is in high demand by both aquatic and terrestrial plants, since it is used to build proteins.

•

Bacteria

in soils, water, and sediments perform many steps of the cycle. They are the star players! Check out the complexity of these steps in the graphic on the next slide.

The global nitrogen cycle

Plants take up nitrogen

• • • • Soil bacteria (

nitrifying bacteria

) convert ammonium to nitrate; nitrate is then available for plant uptake Plants incorporate N into proteins and DNA The nitrogen then moves up the food chain Consumers and decomposers release nitrogen as waste; some of this N returns to the air • The next slide explains the special case of

Nitrogen fixation

, by which certain bacteria and cyanobacteria can convert N from the air into N that plants or algae can use.

Nitrogen fixation

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Means of nitrogen fixation

Bacteria of genus

Rhizobium

live in legume root nodules; legumes include clover, peanut, and soybean plants • • The legume provides the bacteria food and a place to live The bacteria, in turn, provide a steady source of usable N for the plant. This is called nitrogen fixation. • • Three other processes also “fix” nitrogen (convert it) • • •

Atmospheric nitrogen fixation

: lightning

Industrial fixation

: in fertilizer manufacturing

Combustion of fossil fuels

• • • •

Human impacts on the nitrogen cycle

Human involvement in the nitrogen cycle is substantial Many of our food crops (corn, wheat, potatoes, etc.) are heavily fertilized, and fertilizer usually contains N produced commercially. A lot of the fertilizer ends up being washed away by rain. This excess N then enters ditches, creeks, rivers, etc.

The same thing happens when lawns are heavily fertilized.

Excess N is also found in car exhaust and industrial exhaust as a product of burning fossil fuels.

Serious consequences of N imbalances:

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Eutrophication

of waterways —this refers to the “overfertilization” due to runoff of excess N. The excess N

greatly stimulates the growth of algae

, eventually choking out other life forms. By the way, where do we get fertilizer?

• N as Nitric acid (acid rain) can destroy lakes, forests (how about acid clouds?) • Atmospheric nitrogen oxides adds to problems such as ozone pollution and stratospheric ozone depletion © 2011 Pearson Education, Inc.