Life in the Ocean Discussion_Week1
Please read the study materials & post discussion board post.
Post 1: Part II-Study Guide question
A mark of a college graduate is the ability to effectively write an educated, or fact-supported, essay.
1. So, let’s get started with your firstfact-supportedessayexplanationto aBIOL 181 Study Guide Questions (version 2020) (lecture notes). Study Guide questions are found at Content > Course Content. The objectives of this discussion: (1)explore this week’s topic in more detail,(2) write a fact-supported essay answer to your assigned weekly Study Guide question(s),and (3) provide you with detailed feedback on your first essay.
a.Before submission, review thegrading rubrictemplate found below the Discussion in a Rubrics hyperlink.Afterthe discussion due date, you can review your completed (1) grading rubric feedback, and (2) grade feedback by using the procedures inthe document ”
How do students see their grading rubric for a discussion
“found at Content > Course Content > Professor’s Corner.
b. SelectStart a New Threadand post your work in the text box with a subject line entitled as “your last name, Ch. xx, Ques. xx”. Do NOT use an attachment or use the Reply function. You must post first before you can read your classmates’ submissions.
c.Satisfy the requirements(e.g. length, format, etc.)in this hyperlinked document “How to effectively write a fact-supported essay”from the Professor’s Corner. Placeyour question(s) in bold font. That document also explains how to determine your assigned Study Guide question(s).
d.The questions you will be answering represent what I consider to be the most important points of our course. These questions, and subsequent answers, will providean excellent study guide for the final exam. So, by doing a good job on your weekly responses, students are freeing their classmates from having to research all the Study Guide question answers.
2.Here is an analogy to what you are doing:You have just been hired for a college-graduate level position in the XYZ Corporation. Your supervisor hires college graduates because he needs personnel who can meet deadlines and write effectively. Now you are expected to draft correspondence with good content and following the corporation’s writing format. This is the first written work you will submit to your new boss. So… how many errors do you want him to have to correct?
4. Respond to a classmate’s posting.Your response must be substantive, not perfunctory, andnot merely a repetition of your classmate’s material. Submit at least 5 sentences and include at least one additional fact, with accompanying APA in-text citation and APA reference list citation.I encourage inclusion of personal anecdotes.
Post 2:
Selection of a Writing Assignment Topic
1. Read the document entitled “BIOL 181 Writing Assignment topics” found in the Writing Assignment Folder under Course Content. Following those directions, decide on your Writing Assignment (W.A.) topic. More than one student may choose the same topic. If you are having trouble deciding on a topic, consider some of these dangerous marine species in this video:
https://www.youtube.com/watch?v=jf9FzSEnj54&feature=youtu.be
2. Propose your W.A. topic by starting a new thread, stating in thesubject line: your last name, type (i.e. traditional term paper, pro and con term paper, PowerPoint presentation), followed by your topic title, e.g. “Whitford, PowerPoint, Coral Reefs”. If you are selecting an individual, event or species, state the individual, event, or species in your submission.
3.See your Syllabus for the deadline of this topic submission. If I make no comment within one week of your posting, you may assume approval of your topic. If you wish to request a change to your topic later in our course, submit the new topic request in a new posting in this W.A. Topic Selection discussion, and alert me with a note in our weekly Q&A note.
4. Once I approve your topic, you will be submittingyour
thesis statement (go to paragraph 3 of the web page)
, introductory paragraph, and outline to the Week 3 Effective Writing Center (EWC) Workshop later than the deadlines listed in your Course Schedule. The EWC will critique your submissions to assist you in improving the quality and effectiveness of your writing. Your EWC submissions are credited as a discussion score.
Post 3: Enrichment Video Discussion
Enjoy these short videos that address topics in this week’s readings. Post youroptionalcomments (no citations required) in this Discussion. Include video title in your comment title.Many previous students stated that watching the Enrichment videosbeforereading the material was a rewarding procedure.
1.Why the Ocean Matters.Covering 72 percent of the Earth and supplying half its oxygen, the ocean is our planet’s life support systemand its in danger. Watch this short National Geographic video to learn why a healthier ocean means a healthier planet, and find out how you can help. Hyperlink:http://video.nationalgeographic.com/video/why-ocean-matters
2.TED Talk: Robert Ballard: The astonishing hidden world of the deep ocean.Ocean explorer Robert Ballard takes us on a mind-bending trip to hidden worlds underwater, where he and other researchers are finding unexpected life, resources, even new mountains. He makes a case for serious exploration and mapping. Hyperlink:https://www.ted.com/talks/robert_ballard_on_exploring_the_oceans#t-6786
3.Deep ocean mysteries and wonders – David Gallo:In the deepest, darkest parts of the oceans are ecosystems with more diversity than a tropical rainforest. Taking us on a voyage into the ocean — from the deepest trenches to the remains of the Titanic — marine biologist David Gallo explores the wonder and beauty of marine life. Hyperlink:https://www.youtube.com/watch?v=Uqly8ERIkHM
4.Oceana: How Saving the Oceans Can Feed the World.Oceans cover 71% of the planet and are the source of life on Earth. Over a billion people, including some of the poorest in the world, depend on the oceans and wild seafood for survival. But our blue planet is under threat. Each day we remove more than the oceans can replenish. We are draining our oceans of life and protein for a hungry planet. The good news is that our oceans are astoundingly resilient. Contrary to popular belief, the sea is not ungoverned. Ten countries control most of the world’s wild seafood catch. We can turn things around if we focus on three goals: ending overfishing, controlling bycatch and protecting our ocean nurseries. Help us ensure that the oceans remain bountiful and beautiful for generations to come. Hyperlink:https://www.youtube.com/watch?annotation_id=annotation_125289995&feature=iv&src_vid=7PIDQNDr-yY&v=GgKPpiyUrOI
5.Symbiosis. Ever wondered how fish manage to clean their teeth despite having no hands? Bertie answers this and a whole host of other fascinating questions as he goes on a voyage of scientific discovery learning all about symbiosis on tropical reefs. Hyperlink:https://www.youtube.com/watch?v=UK1NyTBb70A&t=44s
6.My wish: Protect Our Oceans.Legendary ocean researcher Sylvia Earle shares astonishing images of the ocean — and shocking stats about its rapid decline — as she makes her TED Prize wish: that we will join her in protecting the vital blue heart of the planet. Hyperlink:https://www.ted.com/talks/sylvia_earle_my_wish_protect_our_oceans?utm_campaign=tedspread&utm_medium=referral&utm_source=tedcomshare#t-1054963 Discussion Grading Rubric ver 8.5 Last revised July 28, 2014
BIOL 181: Life in the Oceans Lecture Notes
The text of these lecture notes for the Sea|mester courses Introduction to Marine Biology (v. 3.1),
by Chantale Bgin, Jessica Wurzbacher, Michael Cucknell, and Introduction to Oceanography
(v. 2.1), by Chantale Bgin and Jessica Wurzbacher, are used with the kind permission of the
authors. Images were researched and selected by UMUC BIOL and NSCI faculty.
Table of Contents
1. Introduction: Science and Marine Biology
2. Fundamentals of Ecology
3. Marine Provinces
4. Seawater
5. Tides
6. Biological Concepts
7. Marine Microorganisms
8. Multicellular Primary Producers
9. Sponges, Cnidarians, and Comb Jellies
10. Worms, Bryozoans, and Mollusks
11. Arthropods, Echinoderms, and Invertebrate Chordates
12. Marine Fish
13. Marine Reptiles and Birds
14. Marine Mammals
15. Intertidal Ecology
16. Estuaries
17. Coral Reef Communities
18. Continental Shelves and Neritic Zone
19. The Open Ocean
20. Life in the Oceans Depths
21. Marine Birds and Mammals in Polar Seas
22. Artificial Reefs
23. Marine Protected Areas
24. Impact of Tourism on the Marine Environment
25. The Global Trade of Marine Ornamental Species
BIOL 181: Life in the Oceans Lecture Notes
2
1. Introduction: Science and Marine Biology
(The majority of the text below originally appeared as chapter 1 of Introduction to Marine Biology)
1.1. Science and Marine Biology
Oceans cover 71 percent of the earth, and affect climate and weather patterns that in turn impact
the terrestrial environments. They are very important for transportation and as a source of food,
yet are largely unexplored; it is commonly said that we know more about the surface of the moon
than we do about the deepest parts of the oceans!
Oceanography is the study of the oceans and their phenomena, and involves sciences such as
biology, chemistry, physics, geology, and meteorology. Marine biology is the study of the
organisms that inhabit the seas and their interactions with each other and their environment.
1.2. Brief History of Marine Biology
Marine biology is a younger science than terrestrial biology, as early scientists were limited in
their study of aquatic organisms by lack of technology to observe and sample them. The Greek
philosopher Aristotle was one of the firsts to design a classification scheme for living organisms,
which he called the ladder of life and in which he described 500 species, several of which were
marine. He also studied fish gills and cuttlefish. The Roman naturalist Pliny the Elder published
a 37-volume work called Natural History, which contained several marine species.
Little work on natural history was conducted during the middle ages, and it wasnt until the late
eighteenth century and early nineteenth century that interest in the marine environment was
renewed, fueled by explorations now made possible by better ships and improved navigation
techniques. In 1831, Darwin set sail for a five-year circumnavigation on the HMS Beagle, and
his observations of organisms during this voyage later led to his elaboration of the theory of
evolution by natural selection. Darwin also developed theories on the formation of atolls, which
turned out to be correct. In the early nineteenth century, the English naturalist Edward Forbes
suggested that no life could survive in the cold, dark ocean depths. There was little basis for this
statement, and he was proven wrong when telegraph cables were retrieved from depths
exceeding 1.7 km deep, with unknown life-forms growing on them. In 1877, Alexander Agassiz
collected and catalogued marine animals as deep as 4,240 m. He studied their coloration patterns
and theorized the absorption of different wavelengths at depth. He also noted similarities
between deepwater organisms on the east and west coast of Central America and suggested that
the Pacific and Caribbean were once connected.
Modern marine science is generally considered to have started with the HMS Challenger
expedition, led by the British Admiralty between 1872 and 1876. During a circumnavigation that
lasted 3.5 years, the Challenger sailed on the worlds oceans, taking samples in various
locations. The information collected was enough to fill 50 volumes that took 20 years to write.
The samples taken during the Challenger expedition led to the identification of over 4,700 new
species, many from great depths, and the chief scientist, Charles Wyville Thomson, collected
plankton samples for the first time.
BIOL 181: Life in the Oceans Lecture Notes
3
The Challenger expedition was the start of modern marine biology and oceanography, and is still
to date the longest oceanography expedition ever undertaken. However, modern technology has
allowed us to sample organisms more easily and more effectively and to quantify things more
accurately. Scuba diving and submersibles are used to directly observe and sample marine life;
remote sampling can be done with nets, bottles, and grabs from research vessels, and satellites
are used extensively for remote sensing.
1.3. Why Study Marine Biology?
1.3.1. To Dispel Misunderstandings about Marine Life
Though many people fear sharks, in reality 80 percent of shark species grow to less than 1.6 m
and are unable to hurt humans. Only three species have been identified repeatedly in attacks
(great white, tiger and bull sharks). There are typically only about eight to 12 shark attack
fatalities every year, which is far less than the number of people killed each year by elephants,
bees, crocodiles, or lightning.
1.3.2. To Preserve Our Fisheries and Food Source
Fish supply the greatest percentage of the worlds protein consumed by humans, yet about 70
percent of the worlds fisheries are currently overfished and not harvested in a sustainable way.
Fisheries biologists work to estimate a maximum sustainable yield, the theoretical maximum
quantity of fish that can be continuously harvested each year from a stock under existing
(average) environmental conditions, without significantly interfering with the regeneration of
fishing stocks (i.e., fishing sustainably).
1.3.3. To Conserve Marine Biodiversity
Life began in the sea (roughly 3-3.5 billion years ago), and about 80 percent of life on earth is
found in the oceans. A mouthful of seawater may contain millions of bacterial cells, hundreds of
thousands of phytoplankton, and tens of thousands of zooplankton. The Great Barrier Reef alone
is made of 400 species of coral and supports over 2,000 species of fish and thousands of
invertebrates.
1.3.4. To Conserve the Marine Environment
Each year, three times as much trash is dumped into the worlds oceans as the weight of the fish
caught. There are areas in the North Pacific where plastic pellets are six times more abundant
than zooplankton. Plastic is not biodegradable and can kill organisms that ingest it. Many
industrial chemicals biomagnify up the food chain and kill top predators. Some chemicals can
bind with hormone receptors and cause sex changes or infertility in fish. Understanding these
links allow us to better regulate harmful activities.
1.3.5. To Conserve the Terrestrial Environment
BIOL 181: Life in the Oceans Lecture Notes
4
Phytoplankton and algae use CO2 dissolved in seawater in the process of photosynthesis, and
together are much more important than land plants in global photosynthetic rates. Marine
photosynthesizers therefore have the ability to reduce the amount of CO2 dissolved in the oceans
and consequently in the atmosphere, which has important implications for the entire biosphere.
Many marine habitats, such as coral reefs and mangroves, also serve to directly protect coastlines
by acting as a buffer zone, reducing the impact of storm surges and tsunamis that may threaten
human settlements.
1.3.6. For Medical Purposes
Because the architecture and chemistry of coral is very similar to human bone, it has been used
in bone grafting, helping bones to heal quickly and cleanly. Echinoderms and many other
invertebrates are used in research on regeneration. Chemicals found in sponges and many other
invertebrates are used to produce several pharmaceutical products. New compounds are found
regularly in marine species.
1.3.7. For Human Health
Several species of plankton are toxic and responsible for shellfish poisoning or ciguatera.
Understanding the biology of those species allows biologists to control outbreaks and reduce
their impact on human health.
1.3.8. Because Marine Organisms Are Really Cool
Many fish are hermaphrodites and can change sex during their lives. Others, including several
deep-sea species, are simultaneous hermaphrodites and have both male and female sex organs at
the same time.
The blue whale is the largest animal to have ever live on earth, and has a heart the size of a
Volkswagen Beetle.
An octopus recently discovered and as of yet unnamed has the ability to mimic the color and
behavior of sole fish, lionfish, and sea snakes, all toxic animals, which greatly reduces its
likelihood of encountering predators.
1.4. How Is Marine Biology Studied? Using the Scientific Method
1.4.1. Science
The word science comes from the Latin (scientia) and means knowledge. Science is a
systematic enterprise that builds and organizes knowledge in the form of testable explanations
and predictions about the world.
1.4.2. The Scientific Method
BIOL 181: Life in the Oceans Lecture Notes
5
The scientific method is widely used in the process of conducting science. Its general steps are to
make observations, form a hypothesis to explain the patterns seen, perform experiments to test
the hypothesis, and then draw conclusions (Figure 1.1).
Diagram showing the steps of the scientific method
by Erik Ong is licensed under CC BY-SA 3.0
Figure 1.1. Scientific method. Steps of the scientific method.
1.5. Review Questions: Introduction to Marine Biology
http://commons.wikimedia.org/wiki/File%3AThe_Scientific_Method.png
http://creativecommons.org/licenses/by-sa/3.0/
BIOL 181: Life in the Oceans Lecture Notes
6
1. What percentage of the earth is covered with oceans?
2. What was the driving force behind the initial studies into oceanography?
3. Who was the scientist on board the HMS Beagle in 1831?
4. What theories did this scientist develop?
5. In the early nineteenth century, who proposed that no life could live in the deep ocean?
6. Who was the chief scientist on board the HMS Challenger from 1872 to 1876?
7. What theories did Alexander Agassiz develop?
8. Why study marine biology? Give three reasons.
9. Explain the process of the scientific method.
BIOL 181: Life in the Oceans Lecture Notes
7
2. Fundamentals of Ecology
(The majority of the text below originally appeared as chapter 2 of Introduction to Marine Biology)
2.1. Study of Ecology
Ecology (from Greek oikos meaning home) is the study of interactions of organisms with each
other and with their environment.
Ecosystems are composed of living organisms and their nonliving environment, while the
biosphere includes all of the earths ecosystems taken together.
The environment is all the external factors that act on an organism:
physical (abiotic): temperature, salinity, pH, sunlight, currents, wave action, and sediment
biological (biotic): other living organisms and their interactions, e.g., competition and
reproduction
The habitat is the specific place in the environment where the organism lives; e.g., rocky or
sandy shore, mangrove, coral reefs. Different habitats have different chemical and physical
properties that dictate which organisms can live there.
Niche: what an organism does in its environmentrange of environmental and biological factors
that affect its ability to survive and reproduce
physical: force of waves, temperature, salinity, moisture (intertidal)
biological: predator/prey relationships, parasitism, competition, organisms as shelter
behavioral: feeding time, mating, social behavior, young bearing
2.2. Environmental Factors that Affect the Distribution of Marine Organisms
2.2.1. Maintaining Homeostasis
All organisms need to maintain a stable internal environment, even though their external
environment may be changing continuously. Factors such as internal temperature, salinity, waste
products, and water content all need to be regulated within a relatively narrow range if the
organism is to survive. This regulation of the internal environment by an organism is termed
homeostasis. The ability to maintain homeostasis limits the environments where an organism can
survive and reproduce. Each species has an optimal range of each environmental factor that
affects it. Outside of this optimum, zones of stress exist where the organism may fail to
reproduce. At even more extremes lie zones of intolerance, where the environment is too extreme
for the organism to survive at all.
2.2.2. Physical Environment
Sunlight
BIOL 181: Life in the Oceans Lecture Notes
8
Sunlight plays an essential role in the marine environment. Photosynthetic organisms are the
base of nearly every food web in the ocean and are dependent upon sunlight to provide energy to
produce organic molecules. Light is also necessary for vision, as many organisms rely on this to
capture prey, avoid predation, and communicate, and for species recognition in reproduction.
Excessive sunlight can, however, be detrimental to some life forms, as it may increase
desiccation in intertidal areas and induce photo-inhibition through pigment damage to
photosynthetic organisms in the very top of the water column.
Click the link to see a graph showing the ranges of environmental “comfort zone.” Where planets
are concerned, the central location is referred to as the “Goldilocks Zone”: not too hot, not too
cold range of conditions for organisms.
Temperature
Most marine organisms are ectotherms (meaning that they rely on environmental heat sources)
and as such are increasingly active in warmer temperatures. Marine mammals and birds, on the
other hand, are endotherms and obtain heat from their metabolism. To keep this heat, they often
have anatomical adaptations such as insulation. The temperature of shallow subtidal and
intertidal areas may be constantly changing, and organisms living in these environments need to
be able to adapt to these changes. Conversely, in the open oceans and deep seas, the temperatures
may remain relatively constant, so organisms do not need to be as adaptable.
Salinity
Salinity is the measure of the concentration of dissolved organic salts in the water column and is
measured in parts per thousand (). Organisms must maintain a proper balance of water and
salts within their tissue. Semipermeable membranes allow water but not solutes to move across
in a process called osmosis. If too much water is lost from body cells, organisms become
dehydrated and may die. Some organisms cannot regulate their internal salt balance and will
have the same salinity as their external environment; these are termed osmoconformers. These
organisms are most common in the open ocean, which has a relatively stable salinity. In coastal
areas where the salinity may change considerably, osmoregulators are more common.
Pressure
At sea level, pressure is 1 atm. Water is much denser than air, and for every 10 meters descent
below sea level, the pressure increases by 1 atm. Thus, the pressure at 4,000 m will be 401 atm,
and in the deepest part of the oceans at nearly 11,000 m, the pressure will be about 1,101 atm.
The pressure of the water may affect organisms that both live in or visit these depths. Organisms
found in the deep oceans require adaptations to allow them to survive at great pressures.
Metabolic Requirements
Organisms need a variety of organic and inorganic materials to metabolize, grow, and reproduce.
The chemical composition of saltwater provides several of the nutrients required by marine
organisms. Nitrogen and phosphorous are required by all photosynthesizing plants or plant-like
http://www.cffet.net/eco/2.1.JPG
BIOL 181: Life in the Oceans Lecture Notes
9
organisms. Other minerals such as calcium are essential for the synthesis of mollusk shells and
coral skeletons. Although nutrients are essential for life, excessively high levels of nutrients in
sea water can cause eutrophication. This process of nutrient enrichment can lead to vast algal
blooms that eventually die and start to decompose. The decomposition may deplete the available
dissolved oxygen in the water, killing fish and other organisms.
2.3. Populations and Ecology
Population: a group of organisms of the same species that occupies a specific area. Different
populations are separated from each other by barriers that prevent organisms from breeding.
Biological community: populations of different species that occupy one habitat at the same
time. The species that make up a community are linked in some way through competition,
predator/prey relationships and symbiosis.
2.3.1. Population Range and Size
Since biologists cant count every single individual in a population, they must instead estimate
size by sampling. One common way to sample a population is to count all individuals within a
few representative areas, and then extrapolate to the total number of individuals that are likely to
be in the entire range. Of course, this method only works well if the samples are representative of
the overall density of the population; if you happen to sample areas of exceptionally high
density, you would overestimate population size. Another common method to estimate
population size is the mark-recapture method. In this process, a certain number of individuals are
captured and tagged, then released back and allowed to mingle with the rest of the population.
After a certain period, a second sample is taken. As long as the marked individuals are dispersed
well within the population and havent suffered mortality from the first capture, the ratio of
marked: unmarked individuals in the second capture should reflect the ratio of marked: unmarked
individuals in the entire population. (Click the link to see a graphic demonstrating a simple mark
and recapture model for determining population density and distribution.) Therefore, we can
estimate population size with the following formula:
M m
—– = —–
N R
where:
N = Population size
M = Number of animals captured and marked in first sample
R = Number of animals captured in resampling event
m = Number of “R” that were already marked
2.3.2. Distribution of Organisms in a Population
Population density refers to the number of individuals per unit area or volume. In many
populations, individuals are not distributed evenly, and the dispersion (pattern of spacing among
http://cascadiaresearch.org/SPLASH/SPLASH-Education/images/markandrecapture.jpg
http://cascadiaresearch.org/SPLASH/SPLASH-Education/images/markandrecapture.jpg
BIOL 181: Life in the Oceans Lecture Notes
10
individuals) can tell a lot about the spacing of resources and interactions between individuals. A
clumped dispersion pattern may reflect variations in the physical environment, or a clumped food
source; a uniform distribution is often the result of strong intraspecific competition; random
dispersion reflects weak interactions among individuals.
2.3.3. Changes in Population Size
Populations change in size over time. They acquire new individuals through immigration and
births, and lose individuals through emigration and deaths. Different species can have varying
reproductive outputs, life span and generation times, all of which can affect how quickly
populations of that species can grow. Collectively, these traits and others that impact births,
deaths and reproduction are referred to as life history traits. On each extreme of a continuum of
life history, strategies are r-selected species (those that have short generation times, high
reproductive potential) and K-selected species (those that have much longer generation time and
are long-lived, but have low reproductive outputs and low population growth potential. The
typical traits of r- and K-selected species are outlined in table 2.1.
Table 2.1. Characteristics of Organisms that Are Extreme r or K Strategists
r
Unstable Environment; Density-
Independent
K
Stable Environment; Density-Dependent
Interactions
organism is small organism is large
energy used to make each individual is low energy used to make each individual is high
many offspring are produced few offspring are produced
organisms have early maturity organisms have late maturity, often after a
prolonged period of parental care
organisms have a short life expectancy organisms have a long life expectancy
each individual reproduces only once individuals can reproduce more than once in a
lifetime
organisms have a type III survivorship pattern,
in which most die within a short time, but a
few live much longer
organisms have a type I or II survivorship
pattern, in which most live to near the
maximum life span
Source: Adapted from University of Miami Department of Biology. Accessed July 15, 2014, from
http://www.bio.miami.edu/tom/courses/bil160/bil160goods/16_rKselection.html
BIOL 181: Life in the Oceans Lecture Notes
11
Populations change in size due to births, deaths, immigration, and emigration. Click here for a
graphic showing various factors that influence population size.
2.3.4. Population Growth
There are many ways in which a population can increase in size, including reproduction and
immigration. When a population has sufficient food or nutrients and is not greatly affected by
predation, it can grow rapidly in an exponential curve. However, no population can maintain this
growth foreverat some point resources become limited and slow down population growth
(either through lower birth rate or increased death rate). That population growth model is called
logistic growth. Here, the population levels off at size which the environment can sustain, known
as the carrying capacity of the environment. The carrying capacity is a dynamic point which may
fluctuate with changes in resource availability and predator behavior. Predator abundance often
mirrors prey abundance with somewhat of a lag in time. Click here to see a graph of exponential
(geometric) and logistic growth curves.
2.4. Communities
A biological community comprises the various populations of different species that interact
together in the same place at the same time. Organisms in a community interact with one another
in a variety of ways.
2.4.1. Niche
The niche of an organism is often described as its role in the community. It refers to the
environmental conditions and resources that define the requirements of an organism. The
broadest niche that an organism can occupy (defined mostly by resource availability and
tolerance to abiotic factors, e.g., pH, salinity) is called its fundamental niche. In reality,
organisms often occupy a smaller subset of their fundamental niche because of biological
interactions with other species such as competition and predation. This subset is called the
realized niche. Click the link to see a graphic indicating the difference between realized and
fundamental niches in nature and how these zones are determined.
2.4.2. Biological Interactions
Competitionoccurs when organisms require the same limiting resources such as food, space
or mates. Interspecific competition occurs between organisms of different species, whereas
intraspecific competition is between organisms of the same species. Interspecific competition for
resources prevents different species from occupying exactly the same niche; if two species have
the same requirements, one will outcompete the other with several possible results: local
extinction (also known as competitive exclusion), displacement of the less successful competitor,
or selection for speciation that would lessen the competition.
To efficiently take advantage of a common resource, organisms may have unique anatomical and
behavioral specializations. This is commonly seen on coral reefs. For example, fairy basslets,
brown chromis, and soldierfish are all plankton feeders, but they do not directly compete with
https://www.mun.ca/biology/scarr/Logistic_growth.gif
https://www.mun.ca/biology/scarr/Logistic_growth.gif
http://www.asdk12.org/staff/vanarsdale_mark/pages/mrva/marine/Marine_E
