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Introduction to the Living World

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Valerie Head

on 21 October 2014

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Transcript of Introduction to the Living World

UNIT 2- CH 3, 4, 5
study of living organisms and how
they interact with biotic and abiotic
components of the ecosystem.
3 basic processes to allow life to exist:
1. One Way Flow of Energy from the sun
-Energy from sun arrives at earth in the form
of solar radiation (visible light, infrared radiation, UV)
-Only 0.1% is captured by producers to start the food web
-Solar energy that warms the earth also generates wind
patterns and causes evaporation of water
-As solar radiation is utilized, low quality heat is released
What are these laws called?
2. Cycling of Nutrients
-Earth acts as a closed system for matter
-Therefore, there is a fixed supply of nutrients
on the planet that must be continually recycled
3. Consistent Force of Gravity
-holds atmosphere close to Earth
-facilitates flow of nutrients and water
Earth's 4 Major Systems
- bottom layer, weather, 0-17km
78% N, 21% O, and greenhouse gases
GHG include water vapor, CO2, and CH4
- next layer, ozone (O3) layer

*The warming and protection from these layers makes
life possible on Earth!
Includes all layers of atmosphere, hydrosphere, and geosphere where life exists.
Divided into biomes, marine life zones, and freshwater life zones
consists of all of the water available on the planet including liquid, ice, and water vapor
- consists of earth's
crust, mantle, and core
Crust and mantle= soil & rock systems that house nonrenewable fossil fuels and minerals, and nutrients
ecosystem structure
Earth's life zones organized into
based on
factors. These factors determine which
will be successful.
Organisms can live only within a specific
range of tolerance
for physical and chemical variations.
vs. Optimum Range
in the absence of
limiting factors
ex: nitrates and phosphates are often
limiting factors in plant growth
Energy Flow in Ecosystems
Organisms in an ecosystem are organized into a hierarchy of feeding orders called trophic levels.
mostly through
phytoplankton that float on surface of ocean are important global producers
others can survive without sunlight through
like in hydrothermal vents
rely on production of energy
aerobic respiration
turns the food that is eaten to energy (ATP)
bacteria and fungi
can break down organic compounds without oxygen through
anaerobic respiration
Types of consumers:
Primary Consumers
Secondary Consumers
(carnivores and omnivores)
Tertiary Consumers
(top predators)
Food Chain vs Food Web
Chemical energy is stored in the organism's

= the dry weight of all of the organic
matter within an organism
provides a measure of how much energy is
available to the next trophic level
Ecological Efficiency
refers to the % of usable chemical energy that is transferred as biomass from one trophic level to the next
**2nd Law of Thermodynamics**
-most of this energy transferred between trophic levels is lost as HEAT
in general 90% of usable energy is lost as HEAT and
only 10% of energy is passed on to the next trophic level
10 kcal
100 kcal
1,000 kcal
10,000 kcal
How can we measure available energy from producers?
Gross Primary Productivity (GPP)-
rate at which producers convert solar energy to chemical energy through photosynthesis
However, since some available chemical energy is lost through respiration, a better measurement to determine the available energy for higher trophic levels is to measure
Net Primary Productivity (NPP).

NPP = GPP - Respiration
Primary Productivity is highest in tropical rain forests and estuaries.
In general, as you move away from the equator primary productivity will decrease. Therefore biodiversity will also decrease due to lack of available energy.
Biogeochemical Cycles
Six major elements make up the majority of biomass in living organisms.
S. P. O. N. C. H.
These elements continuously cycle as biomass is consumed, assimilated, decomposed, or combusted.
Hydrologic Cycle
Carbon Cycle
Nitrogen Cycle
Phosphorus Cycle
Sulfur Cycle
As nutrients move through ecosystem, they may accumulate in locations for long periods of time.
These areas are known as
and commonly include the atmosphere, water, or soil and rock.
human activities
alter these natural cycles therefore impacting population growth.
Human Impact on the Hydrologic Cycle
Removing large amounts of water for societal and industrial uses
Increased Change of Flooding:
Removing large areas of wetlands or creating new non porous tracts of land (parking lots, roads) which decrease the Earth's natural absorptive abilities and increase erosion.
Clearing large amounts of vegetation decreases transpiration rates, which can decrease precipitation
Human Impact on the Carbon Cycle
Burning of Fossil Fuels:
burning of coal, oil, and natural gas releases CO2 (a greenhouse gas)
Clear- Cutting:
removing large tracts of forest, especially in tropical regions, faster than they can grow back decrease the amount of CO2 that is naturally stored in plants
Human Impacts on the Nitrogen Cycle
Excess Nitrates:
nitrates from animal feedlot waste and municipal sewage discharge runs off into waterways. Extra nutrients create anoxic (low dissolved oxygen) which depletes aquatic biodiversity
Burning of Fossil Fuels:
burning these fuels releases NO and is converted to NO2, a raw material for photochemical smog, and HNO3 is a contributor to acid rain
Using Inorganic Fertilizers:
by adding large amounts of inorganic fertilizer, we increase denitrification by bacteria, which release N2O into the atmosphere which increase global warming
Human Impacts on the Phosphorus Cycle
Phosphate Runoff:
excess phosphate runs off into waterways from fertilizers, mining waste, and sewage This leads to algal blooms which decreases oxygen in the water (eutrophication), therefore depleting aquatic biodiversity
Human Impact on the Sulfur Cycle
Release of Sulfur Dioxide:
SO2 is added to the atmosphere in several ways-
S is an impurity in coal and petroleum, so when it is burned it is released
SO2 can form H2SO4 contributes to acid rain
Currently scientists have named 1.8 million different species?
Do you think there are more out there?
If so, why haven't we found them?
= variety of species, the genes they contain, and the ecosystems they live in.
Where are the most species concentrated?
Why do you think that is?
Highly diverse ecosystems =
more stable and able to withstand environmental change
The variety of life serves to provide
natural capital
ecological services
So how can we measure biodiversity?
- the
species diversity
of any area is the number of
different species in one area at any given time
) combined with the abundance of individuals within
each of those species (
species evenness
N Fixation- N2 in atmosphere to ammonia by bacteria in the soil

Ammonification- decomposers convert organic remains into ammonia

Nitrification- bacteria converts ammonia into nitrates

Denitrification- bacteria convert ammonia back into N2 gas and N2O
Species today are equipped with a myriad of unique and complex
for survival.

(random changes in DNA) have provided the means for genetic variability between populations and within the same species.
So, the question is: How have these small changes in an organism's DNA lead to the abundant amount of biodiversity that we have today?
Charles Darwin

answers this question in his detailed descriptions and evidence of the concept of

natural selection
Natural Selection
is the mechanism for
This is EVOLUTION in a nutshell:
Some organisms have traits or genes that give them an increased chance for survival. Therefore they are more likely to reproduce often and pass on those successful genes. Those organisms without the advantageous genes will likely not survive and reproduce, therefore the unsuccessful genes will not be passed on.
The genetically inheritable traits that make an organism more likely to survive and reproduce are known as
Therefore the change in genetic makeup over time is referred to as
Typically natural selection produces small changes in genetic make up of a population over time. However, in some cases these selective forces can lead to an entirely new species=
: It is populations that evolve over time by becoming genetically different- not individuals!
Geologic and Climatic changes impact Natural Selection.
1. Tectonic Activity &
Movement of Continents
2. Earthquakes and Volcanoes
1. Periods of Warming and Cooling
2. Changes in Sea Levels
3. Glaciers form and recede
4. Locations of biomes shift
So how do new species arrive from these changes?
Geographic Isolation
- events can physically separate populations, populations are now exposed to different environmental pressures possibly making previously unsuccessful traits now more successful
Reproductive Isolation
- inability to pass new traits between separated populations (ex: mating at different times of the year)
N is essential for life because it is a component of proteins, vitamins, and nucleic acids.
As these geologic and climatic changes take place, some organisms don't survive.
Background Extinction vs. Mass Extinction
low level of extinction that may even not be noticed, happens all of the time
large groups of species are wiped out
Extinction opens up
that were previously filled.
Generalist Species
- broad niches because they have a variety of food sources and a wide range of tolerance for environmental conditions
EX: roach, rat, kudzoo
Specialist Species

narrow niches, feed only on 1 food source, and tolerates a small range of tolerance of environmental conditions.
EX: orchid mantis, koala
Native Species vs. Invasive Species
Organism that typically lives and flourishes in a certain environment
Organisms that are introduced either intentionally or accidentally to a new environment.
species make for successful
invasive species
because they usually face little predation, disease, can eat a variety of foods, etc. They can possibly out-compete the native species which can devastate the natural ecosystem.
Keystone Species
- some species play an extremely
vital role
in maintaining the integrity of the ecosystem. The
of a keystone species would have a
larger impact
on the community because it may fill a variety of ecological roles.
EX: Pollinators, Predators (American Alligator, Sea Otters)
Indicator Species
- provide an early
that damage to an ecosystem is occurring. They are typically
to change.
EX: lack of sensitive macro invertebrates warn of water pollution
also, amphibians good indicator species because they live in water and on land
In biologically diverse areas, it is not uncommon for the niche of 2 species to overlap.

So what happens?
Competitive Exclusion Principle
- no 2 species can occupy the same niche or they will compete for resources
Therefore, there are 5 main interactions among species:
Interspecific Competition
- 2 or more DIFFERENT species competing for the same resource
Intraspecific Competition
- competition between organisms of the SAME species
- predator feeds on prey

*both have unique survival skills
1. Pursuit and Ambush
2. Mimicry
3. Camouflage
4. Chemical Warfare
**Coevolution- evolve in response to the other's adaptations for survival
- one organism benefits, the other is harmed
- both organisms benefit
- one organism benefits, the other doesn't care
We know that environments are always changing due to events like
fires, volcanoes, climate change, or habitat loss...
The gradual change in species abundance and biodiversity after such events is known as
Two types of Ecological Succession:
Primary Succession
- establishment of a community from a
previously life-less terrain (or bare rock)
*lava flow that solidifies or a receding glacier that
exposes bare rock
Secondary Succession
- a disturbance in an ecosystem has damaged part of the established community, but leaves in place the soil and sediments

*forest fires, major storms, natural disasters, clear-cutting,
abandoned neighborhoods
*Pioneer species

(lichen and moss)- 1st to inhabit the area
As ecosystems change, the population
size, density, distribution, and age structure
of species will also change.
Factors such as availability of nutrients (nitrates, phosphates, water), abundance of predators, diseases, and human activities can also change population dynamics.
Changing Populations:
1. Distribution
2. Size
3. Growth
Populations have various distribution or dispersion patterns:
1. Random
2. Clumped
3. Uniform
Which do you think is most common?
Most communities live in clumps or patches as they gather around nutrients or resources. They may also be clumped for protection, hunting, or even collaborative care of their young.
Change in Population Size Formula:
N = (birth + immigration) - (death + emigration)
Ecologists also predict the future of a population by examining the
age structure
of a population.
If the majority of the population is pre-reproductive or in reproductive years, what does that tell you about future growth?

If the majority of the population is in post-reproductive years, then what will that tell you about future growth?
Populations typically show two growth patterns:
Exponential Growth
- populations grow at their intrinsic rate
of increase and are NOT limited by resources
Logistic Growth
- Initial rapid growth will level off due to
declining resources
*This upper limit is called
1. Pioneer Species
2. Have many offspring
3. Come to maturity and reproduce early
4. Capable of withstanding environmental changes
5. Fluctuate wildly above and below carrying capacity
6. Adults are typically small
7. Little to no parental care for their offspring
8. Generalists
9. Low ability to compete
Examples of r-selected species:
1. Late successional species
2. Have fewer, larger offspring
3. Later reproductive age
4. Not capable of withstanding environmental change
5. Population will stabilize near carrying capacity
6. Adults are typically larger in size
7. Give some type of parental care
8. High ability to compete
Examples of K-selected species:
- increase in concentration of DDT, PCBs, and other slowly degradable, fat soluble chemicals in organisms at successively higher trophic levels of a food change or food web.
- these chemicals accumulate in the fat cells of organisms, causing biomagnification to take place
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