OUR OCEAN PLANET
OUR OCEAN PLANET
SECTION 3 – LIFE IN THE OCEANS
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3. LIFE IN THE OCEANS
3. LIFE IN THE OCEANS
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3.1 OCEAN LIFE
3.1 OCEAN LIFE
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3.1 OCEAN LIFE
3.1 OCEAN LIFE
3.1.1 Origin Of Life
The story of the origin of life on Earth goes almost as far back as
when the Earth itself was young about 4,500 million years ago
(MYA).
Geologists have segregated Earth’s long historical timeline into a set
of divisions called Eons, Eras, Periods and Epochs. The divisions
are drawn based on certain key events that occurred towards the
end of each division and caused a dramatic shift in the number and
type of species in the oceans and on Earth.
This information is largely drawn from studying fossils, and
continues to be modified and corrected as geologists and other
scientists obtain and analyze more data. Each geologic time period
can be characterized by specific land forms and climates, animals
and plants.
The rest of this section describes our understanding of some key
events that occurred in the Precambrian when life first formed in the
ocean.
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3.1 OCEAN LIFE
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3.1 OCEAN LIFE
PRECAMBRIAN – 4,500 MYA TO 543 MYA
The early Earth about 4,500 million years ago was very different
from today because it had no ocean or air and was constantly
bombarded by planetoids and other materials left over from the
formation of the solar system. This bombardment, combined with
heat from radioactive breakdown and heat from the pressure of the
planet’s contraction, caused the Earth to be fully molten during early
Hadean time.
The Earth Cools
Over time, the Earth cooled. Molten material began solidifying into
rock and continental plates began to develop during the Archaean
Era about 3,800 million years ago.
Early Atmosphere
The atmosphere during the Archaean was composed of methane,
ammonia and other gases which would be toxic to most life on Earth
today. The atmosphere also contained a great deal of water vapor
which became liquid as it cooled.
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3.1 OCEAN LIFE
Early Life
By examining some of the oldest sedimentary rocks on Earth,
scientists have concluded that life on Earth started in the ocean. Life
first appeared on Earth early in the Archaean. The oldest fossils date
to roughly 3,500 MYA and consist of bluegreen bacteria. In fact, all
life on Earth for the next 1,000 million years was probably bacterial.
By about 2,500 MYA, during the Proterozoic Era, abundant fossils of
living organisms, mostly blue-green bacteria, can be found. Then,
about 1,800 MYA, simple eukaryotic cells (cells with a nucleus)
started appearing.
Late Atmosphere
The middle Proterozoic saw an oxygen buildup in the atmosphere
which was probably caused by photosynthetic organisms in the
oceans. Photosynthesis is the process by which organisms (e.g.
blue-green bacteria, green algae, and plants) use carbon dioxide,
water and sunlight to produce carbohydrates and oxygen as a byproduct. Carbon dioxide, nitrogen and ozone levels also built up.
The atmosphere’s ozone layer formed which screened developing
life from the effects of the Sun’s ultraviolet radiation. This
atmosphere made possible the explosion of new life forms toward
the end of the Proterozoic, including multi-cellular algae and
animals.
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3.1 OCEAN LIFE
First Multi-Cellular Animals
One of the oldest known groups of multi-cellular animals is the
cnidarians, which include the sea anemones, corals, hydroids,
siphonophores, true jellyfish and box jellyfish. Fossil records date
back to the Precambrian (about 550 MYA).
REFERENCES & FURTHER READING
http://www.ucmp.berkeley.edu/help/timeform.html
http://www.fossils-facts-and-finds.com/geologic_time_line.html
Ocean Literacy Principle 4(a)
Most of the oxygen in the
atmosphere originally came from
the activities of photosynthetic
organisms in the ocean.
Ocean Literacy Principle 4(b)
The first life is thought to have
started in the ocean. The earliest
evidence of life is found in the
ocean.
3.1 OCEAN LIFE
3.1.2 Extreme Ocean Life
Ocean life is full of extremes with some of the most ancient,
smallest, largest, and most poisonous creatures found there.
MOST ANCIENT
Some of the oldest organisms include the blue-green bacteria which
are about 3,600 million years old. Some of the oldest multi-cellular
animals are the cnidarians which are about 550 million years old. In
contrast, recognizable humans are only about 2 million years old.
SMALLEST ANIMALS
Some of the smallest organisms found in the oceans include viruses,
bacteria and other microbes.
LARGEST ANIMALS
The largest creature that has ever lived on Earth is the blue whale.
Adult females are the largest and measure 33m (108 ft) in length.
Their tongue alone weighs the same as an elephant. The lion’s
mane jellyfish can also be very long reaching 30m (100 ft) in length.
OLDEST ANIMAL
Recent research has pointed to a species of clam as being the
oldest creature alive. A clam dredged up off the coast of Iceland is
thought to be the longest-lived mollusc discovered. Scientists
estimated that the ocean quahog was aged between 405 and 410
years old. The clam was nicknamed “Ming” after the Chinese
dynasty that was in power when it was born.
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3.1 OCEAN LIFE
LARGEST PREDATOR
The largest predator is the sperm whale (Physeter macrocephalus).
It is also the largest of the toothed whale species. Males are usually
about twice as large as the females. Adult males can grow up to 18
m (60 ft) long and weigh 36,300 kg (80,000 lbs). They have a long
life span living up to 70 years. Sperm whales have been found living
in every ocean in the world. Sperm whales have strong conical
(cone shaped) teeth in their lower jaw and only remnants of teeth in
the upper jaw. The largest teeth are 28 cm (11 in) long and used
when hunting prey such as giant squid. Herman Melville’s sea-faring
adventure, written in 1851, features the “white sperm whale” known
as “Moby Dick”.
LARGEST PREDATORY FISH
The largest predatory fish known is probably the Megalodon shark.
At a length of more than 15 m (50 ft), Megalodon was larger and
heavier than Tyrannosaurus rex and had teeth 18 cm (7 in) long.
Megalodon is the largest predatory fish that has ever lived and is
second only to the sperm whale as the largest predator our planet
has ever produced. In comparison, the great white shark is “only” 7
m (23 ft) in length.
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3.1 OCEAN LIFE
MOST POISONOUS
The most poisonous animals are probably either sea snakes or box
jellyfish, which are both found in Australia. Being bitten by a sea
snake or stung by a box jelly, such as the finger-nail sized Carukia
barnesi, can be fatal to humans with death occurring in minutes. Box
jellyfish are also found in the Caribbean Sea and while their stings
are less dangerous than their Australian relatives, they are still very
potent.
DEADLIEST
In the ocean, candidates for the deadliest creatures include killer
whales, some sharks (e.g. bull shark, great white shark or tiger
shark), sea snakes or box jellyfish. On land, spiders (e.g. funnel web
spiders) or snakes (e.g. cobras) are the most deadly. More subtly,
humans, mosquitoes, tsetse flies or other disease-carrying insects
can also be considered deadly.
Ocean Literacy Principle 5(a)
Ocean life ranges in size from
the smallest virus to the largest
animal that has lived on Earth,
the blue whale.
REFERENCES & FURTHER READING
http://www.extremescience.com/sperm-whale.htm - Sperm whale
http://www.elasmo-research.org/education/evolution/size_megalodon.htm - Megalodon shark
http://news.bbc.co.uk/1/hi/sci/tech/7066389.stm - Ming the clam is oldest mollusc (Oct/28/2007)
3.1 OCEAN LIFE
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3.1.3 Classification
All living organisms can conveniently be grouped together in a number of ways. One traditional way to
group organisms is to compare internal and external features of an organism and group them according
to these features.
GROUPS
At the top level, all organisms are placed into one of five groups called “kingdoms” as follows:
1. Monera – prokaryotes (includes Eubacteria and Archaebacteria)
2. Protista – protists
3. Fungi – fungi and related organisms
4. Plantae – plants
5. Animalia – animals
Kingdoms are further divided into groups called phyla (plural; phylum – singular). Each phylum is divided
into classes, each class into orders, each order into families, each family into genera, and each genus
into species as follows:
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species
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3.1 OCEAN LIFE
Some examples of these major groups are illustrated below:
Kingdom
Animalia
Plantae
Protista
Phylum
Chordata
Tracheophyta
Amoebozoa
Class
Mammalia
Angiosperm
-
Order
Cetacea
Najadales
Euamoebida
Family
Physeteridae
Hydrocharitaceae
Amoebidae
Genus
Physeter
Thalassia
Amoeba
Species
macrocephalus
testudinum
proteus
At the bottom level, the genus and species name uniquely identify the organism. A species represents
one type of organism, such as Physeter macrocephalus (sperm whale), Thalassia testudinum (turtle
grass) or Amoeba proteus (the common amoeba).
3.1 OCEAN LIFE
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Conventionally, the genus (e.g. Physeter) is written in upper case and the species (e.g. macrocephalus)
is in lower case. The genus and species is also underlined or italicized. Well-known examples include
Homo sapiens (humans), Orcinus orca (killer whales) and Carcharodon carcharias (great white sharks).
Several variations of the genus and species name are also sometimes used for convenience. If you are
not sure what species an organism is precisely or if it is not particularly relevant, the abbreviation “sp.”
can be used. Thus, if you are referring to some species of the sea grass Thalassia, it might be written
Thalassia sp. Alternatively, if you are referring to several species of the sea grass Thalassia, you might
write Thalassia spp. Finally, if you are referring to the same species repeatedly, it is convenient to
abbreviate the genus name to just an initial with a full stop punctuation mark. For example,
Tyrannosaurus rex is often abbreviated to T. rex.
3.1 OCEAN LIFE
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KEY TO THE 5 KINGDOMS
Biologists develop “keys” to help them determine what an organism is and how to classify it. Suppose
you see something in the ocean that appears to be living. How do you classify it? The following is a key
that you might use to determine which of the 5 kingdoms to which it belongs:
1. Is it green or does it have green parts?
• Yes – go to 2
• No – go to 3
2. It may be a plant, protist or moneran (blue-green bacteria). Make sure that the green is really part of
the organism and not something green an animal might have eaten.
• Is it single-celled? Yes – go to 6
• Is it multi-cellular? Yes – it is a plant (Plantae). Look for cell walls and other internal structures. Under
a microscope you might be able to see chloroplasts.
3. It could be a moneran, protist, fungus, or animal.
• Is it single-celled? – Yes, go to 4
• Is it multi-cellular (look for complex or branching structure, appendages)? – Yes, go to 5
3.1 OCEAN LIFE
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4. It could be a moneran or a protist. Can you see any details inside the cell?
• Yes – it is a protist (Protista). You should be able to see at least a nucleus and/or contractile vacuole,
and a definite shape. Movement should be present, using cilia, flagella, or amoeboid motion. Cilia or
flagella may be difficult to see.
• No – it is a moneran (Monera). It should be quite small and may be shaped like short dashes (rods),
small dots (cocci), curved, or spiral shaped.
5. It could be an animal or a fungus. Is it moving?
• Yes – it is an animal (Animalia). Movement can be by cilia, flagella, or complex, involving parts that
contract. Structure should be complex. Feeding activity may be obvious.
• No – it is a fungus (Fungi). Should be branched, colorless filaments. May have some kind of fruiting
body (mushrooms are a fungus, don't forget). Usually attached to some piece of decaying matter - may
form a fuzzy coating on or around an object.
6. It is probably a protist (Protista) but could be a moneran. Most green protists are flagellates, that is,
they move rapidly with a spiraling motion. It might also be a colonial protist, such as Volvox, which forms
a spinning ball of green cells. However, if it consists of long, unbranched, greenish filaments with no
apparent internal structure, it is probably a blue-green bacterium (sometimes mistakenly called bluegreen alga), a moneran.
3.1 OCEAN LIFE
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Generally, the more closely you observe the organism, the more certain you can be. However, many
living things have stages that make them resemble members of another kingdom. Thus, depending on
when you observe the features and what the precise features are, you may place an organism incorrectly
into a group – classification can be a complicated process.
REFERENCES & FURTHER READING
http://www.ruf.rice.edu/~bioslabs/studies/invertebrates/kingdoms.html
http://www.ucmp.berkeley.edu/archaea/archaea.html
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3.1.4 Major Oceanic Organism Groups
Most life in the ocean exists as micro-organisms or microbes
including bacteria, blue-green bacteria and plankton.
Microorganisms such as blue-green bacteria and phytoplankton
(plant plankton) are the most important primary producers in the
ocean. Not only are they the most abundant life form in the ocean,
they also have extremely fast growth rates and life cycles.
Ocean Literacy Principle 5(b)
Most life in the ocean exists as
microbes. Microbes are the most
important primary producers in the
ocean. Not only are they the most
abundant life form in the ocean,
they have extremely fast growth
rates and life cycles.
We do not know how many species there are in the ocean or,
indeed, on Earth. Estimates range from a few million to as many as
30 million of which we only know a small fraction!
Ocean Literacy Principle 5(c)
Some major groups are found
exclusively in the ocean. The
diversity of major groups of
organisms is much greater in the
ocean than on land.
DIVERSITY
Biodiversity is a measure of the number of species in an ecosystem.
For example, there are many different species of fishes but only a
few species of sea otters. Fishes are, therefore, considered much
more diverse than sea otters.
The diversity of major groups of organisms is much greater in the
ocean than on land with some major groups found exclusively in the
ocean.
One of the most diverse groups of animals in the ocean is the
crustaceans. The crustaceans consist of some 39,000 known
species distributed worldwide. Crabs, lobsters, and shrimps are
among the best-known crustaceans but the group also includes an
Interesting!
The naturalist, J. B. S. Haldane,
was asked by a cleric about what he
might infer about the Creator, based
on his wide ranging study of life.
Haldane supposedly replied “the
Creator, if He existed, must have
had an inordinate fondness for
beetles" based on the then current
count of beetle species at around
400,000.
3.1 OCEAN LIFE
MAJOR OCEANIC ORGANISM GROUPS
The following outlines some of the major groups of organisms found
in the ocean from within the 5 kingdoms:
1. Monera – Prokaryotes (Eubacteria & Archaebacteria)
Prokaryotes are unicellular organisms that lack a true nucleus with
genetic material composed of a single molecule of double-stranded
DNA. Nearly all prokaryotes have a rigid cell wall and may or may
not be able to move. They include bacteria and the blue-green
bacteria (cyanobacteria).
Microbes / bacteria
Blue-green bacteria (e.g. Spirulina)
Prokaryotes are usually microscopic in size although the blue-green
bacteria are larger and resemble algae. Thus, they are green,
filamentous, and quite long but they also have no visible structure
inside the cell. They absorb nutrients through the cell wall or
produce their own through photosynthesis. Blue-green bacteria are
also sometimes called blue-green algae.
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2. Protista (Protists)
Protists are a diverse group of organisms including a variety of
unicellular, colonial and multi-cellular organisms. Protists may move
by cilia, flagella or by amoeboid mechanisms. They usually do not
have a cell wall although some forms may have one. They have
organelles (well-defined structures that have a particular set of
functions within a cell) including a nucleus and may have
chloroplasts so some are green and able to photosynthesize food.
Nutrients are acquired by ingestion of other organisms,
photosynthesis or both. Protists are further divided into three major
groups:
(a) Protozoa (Animal-like protists)
Protozoans are mostly single-celled and motile animals that
feed by phagocytosis. They are usually small (0.01–0.5 mm)
and can conveniently be grouped by method of locomotion into:
Flagellates – with long flagella (e.g. Euglena)
Amoeboids – with transient pseudopodia (e.g. Amoeba)
Ciliates – with multiple, short cilia (e.g. Paramecium)
Sporozoa – non-mobile; form spores (e.g. Toxoplasma)
Important!
Phytoplankton (plant plankton) is a
general term used to describe
microscopic plants in the ocean.
Phytoplankton is composed of
many different species including:
Algae
Diatoms
Dinoflagellates
Blue-green bacteria
3.1 OCEAN LIFE
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(b) Algae (Plant-like protists)
They include single-celled organisms, such as Euglena, that are also
considered protozoa which have acquired chloroplasts. Some, such as
seaweeds, are multi-cellular including members of the following groups:
Chlorophytes – green algae (e.g. Ulva (Sea Lettuce))
Rhodophytes – red algae (e.g. Porphyra)
Heterokontophytes – diatoms, brown algae (e.g. Macrocystis (Kelp))
The green and red algae, along with a small group called the
glaucophytes, appear to be close relatives of plants and some authors
treat them as plants despite their simple organization.
Most other algae, however, developed separately. They include the
haptophytes, cryptomonads, chlorarachniophytes, dinoflagellates, and
euglenids, all of which have also been considered protozoans.
(c) Fungus-like protists
Various organisms with a protist-level organization were originally
treated as fungi, because they produce sporangia (spore producing
structures (capsules) borne on the top of the sporophyte.) These
include chytrids, slime molds, water molds and Labyrinthulomycetes. Of
these, the chytrids are now known to be related to other fungi and are
usually classified with them. The others are now placed among the
heterokonts (which have cellulose rather than chitin walls) and the
Amoebozoa (which do not have cell walls).
Interesting!
The dinoflagellates are difficult
to classify because they have
both animal and plant
characteristics. They can be
considered animals because
they have 2 flagella which they
use to move (an animal
characteristic – plants can’t
move!). However, they also
have chloroplasts which they
use to photosynthesize food (a
plant characteristic – animals
cannot photosynthesize food).
3.1 OCEAN LIFE
3. Fungi (fungi)
Fungi are multi-cellular organisms. Each cell has a several
organelles including a nucleus and a cell wall but they have no
chloroplasts and no mechanisms for locomotion. Most fungi
grow in terrestrial environments but several species occur only
in aquatic habitats. Fungi range in size from microscopic to
very large (e.g. mushrooms). For the most part, fungi acquire
nutrients from decaying material by absorption.
4. Plantae (plants)
Plants are multi-cellular organisms. Each cell has a nucleus,
chloroplasts, and cell walls. Most cannot move although the
gametes of some move using cilia or flagella. They are all able
use sunlight to produce food through photosynthesis.
By the seashore, plants such as mangroves, sea grapes and
palms are of special interest. In the ocean, plants such as sea
grasses are important. Sea grasses are flowering plants from
four plant families that grow in the marine environment:
Posidoniaceae
Zosteraceae
Hydrocharitaceae
Cymodoceaceae
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5. Animalia (animals)
Animals are multi-cellular and move with the aid of cilia, flagella
or muscular organs based on contractile proteins. Animal cells
have organelles including a nucleus but have no chloroplasts
or cell walls. Animals acquire nutrients by ingestion. Some of
the major animal groups found in the ocean include:
(a) Vertebrates (animals with backbones)
Fish
Bony fish – e.g. angelfish, groupers, etc.
Cartilaginous fish – e.g. sharks and rays
Jawless fish – e.g. hagfishes, lampreys
Reptiles
Marine iguanas
Sea turtles
Sea snakes
Alligators & crocodiles
Birds
Puffins
Gannets
Guillemots
Razorbills
Penguins
Gulls
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Mammals
Sea otters
Pinnipeds – true seals, eared seals and walruses
Polar bears
Cetaceans – whales and dolphins
Sirenians – manatees and dugongs
(b) Invertebrates (animals without backbones)
Cnidarians
Sea anemones & corals
Siphonophores
True jellyfish
Box jellyfish
Porifera
Sponges
Crustaceans
Shrimps
Crabs
Lobsters
Barnacles
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3.1 OCEAN LIFE
Molluscs
Clams
Cockles
Mussels
Oysters
Periwinkles
Limpets
Scallops
Nudibranchs
Octopus
Squid
Echinoderms
Sea stars
Sea urchins
Sand dollars
Sea cucumbers
REFERENCES & FURTHER READING
http://www.marinespecies.org – Marine Species Classification
http://biology.missouristate.edu/phycology/images/Spirulina.jpg - Spirulina
http://en.wikipedia.org/wiki/Protist - Protist
http://www.funsci.com/fun3_en/protists/introduction.htm - Protist
http://www.uwgb.edu/biodiversity/biota/arthropods/Arachnids/ - Arachnids
http://www.britannica.com/eb/topic-144848/crustacean - Crustacean
http://www.sms.si.edu/IRLFieldGuide/Seagrasses.htm - Sea Grasses
http://www.sms.si.edu/IRLFieldGuide/Plants.htm - Terrestrial Grass
http://www.edu.pe.ca/southernkings/microbe.htm - Microbes
3.2 RELATIONSHIPS
3.2 RELATIONSHIPS
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3.2 RELATIONSHIPS
3.2 RELATIONSHIPS
Ocean biology provides many examples of life cycles, adaptations
and important relationships between organisms including symbiosis
and predator-prey dynamics.
This section discusses several
important relationships between living organisms and introduces
several basic concepts to the reader.
3.2.1 Adaptation
An “adaptation” is a characteristic that generally increases an
organism's ability to survive within a changing environment.
The following are examples of a variety of adaptations in fish:
1. Mouth, Teeth & Jaws
The mouths, teeth and jaws are adapted to the type of diet that
specific fishes eat.
For example, foureye butterflyfish have long, pointed mouths for
plucking out coral polyps as food. They feed mainly on hard and
soft corals (gorgonians), polychaete worms, and tunicates.
In contrast, morays eels are predators that feed on fishes,
octopuses, crustaceans and molluscs. They have long, sharp teeth
and powerful jaws that can crush bone.
Parrotfish have a parrot-like “beak” from fused teeth and strong jaws
to help them bite into rock-hard coral structures and scrape off the
algae and corals.
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Ocean Literacy Principle 5(d)
Ocean biology provides many
unique examples of life cycles,
adaptations and important
relationships among organisms
(symbiosis, predator-prey
dynamics and energy transfer)
that do not occur on land.
3.2 RELATIONSHIPS
2. Body Shape
Fish body shapes can take many forms such as fusiform (torpedoshaped) for fast open-ocean swimming fish (e.g. tuna) or
flattened/depressed for bottom-dwelling fish (e.g. flounders).
3. Color
Color can be used for many purposes including camouflage, for
disruptive effect to conceal them against their background (e.g.
triggerfishes), for advertising a service (e.g. cleaner fish) or even a
warning (e.g. lionfish)
4. Appendages
Special appendages such as barbels (which look like whiskers) help
fish “feel” for food (e.g. sturgeons, catfish or goatfish).
REFERENCES & FURTHER READING
http://en.wikipedia.org/wiki/Natural_selection
http://evolution.berkeley.edu/evolibrary/home.php
http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_toc_01
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3.2 RELATIONSHIPS
3.2.2 Food Pyramid
All organisms can be thought of as producers or consumers
depending on whether they produce or consume food.
PRODUCERS
Plants and other photosynthetic organisms are producers because
they can produce or make food from sunlight and raw materials. In
the ocean, producers include blue-green bacteria, algae, seaweed,
kelp, phytoplankton (plant plankton) and plants.
CONSUMERS
In contrast, animals are consumers because they consume one
another or plants – they cannot produce anything from sunlight and
raw materials. Humans are consumers because we eat animals and
plants.
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3.2 RELATIONSHIPS
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FOOD PYRAMID
A food pyramid shows the feeding relationship between producers and their consumers. There must
always be more producers than consumers because otherwise you would run out of food. Thus, there
are more plants than primary consumers, more primary consumers than secondary consumers, and
more secondary consumers than tertiary consumers. At the top of the food pyramid, there are very few
animals because it takes so many animals and plants to support them. For example, there are very few
great white sharks because it takes a large number of seals, sea lions, and fish to feed them.
When an animal or a plant becomes extinct, the whole food pyramid is affected. For example, if a plant
goes extinct, the primary consumer that feeds upon it may also go extinct if it cannot find an alternative
food source. Similarly, if a primary consumer goes extinct, a secondary consumer that depends on it
may go extinct which may affect a tertiary consumer in a chain reaction.
An animal that hunts and eats other animals is called a predator while animals that are hunted are known
as prey. An animal that only eats meat is known as a “carnivore” while an animal that only eats plants is
known as a “herbivore”. An animal with a mixed diet is known as an “omnivore”. There must always be
fewer predators than prey otherwise the predators would eventually consume everything and starve. As
a result, there are progressively more animals going down a food pyramid. At the base of the food
pyramid, plants far outnumber animals.
3.2 RELATIONSHIPS
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3.2 RELATIONSHIPS
3.2.3 Predator-Prey
The act of predation is one in which one organism consumes all or
part of another. As such, it can include a normal predator-prey
relationship (e.g. a shark preying on another fish) as well as
herbivore-plant or parasite-host interactions.
These linkages are the prime movers of energy through food chains
and are an important factor in the ecology of populations
determining the mortality of prey and birth of new predators.
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Interesting!
An animal can be both predator and
prey. A tuna that eats other fish is
a predator. However, the tuna is
also prey to sharks. Some sharks
prey on other sharks so sharks can
be both predator and prey.
Predators that are not consumed by
any other animal (such as Great
White Sharks) are known as “top
predators”.
PREDATOR-PREY CYCLES
A coupled predator-prey system will ordinarily cycle. In other words, predator numbers initially increase
when prey are abundant. When prey numbers are driven to down as a result of excessive predation, the
number of predators decline. As the number of predators decline, the number of prey recovers, which
again leads to an increase in the number of predators.
In the lab, predators often extinguish their prey and then starve. In nature, however, at least three
factors promote cycling. First, due to slight variations in an environment, some prey may hide in areas
where they escape detection by predators. Once predators decline, their prey can then fuel a new round
of population increase. Second, prey may also evolve behavior patterns, armor, and other defenses that
reduce their vulnerability to predators. Third, an alternative prey may also provide a kind of refuge
because once a prey population becomes rare, predators be forced to hunt a different prey species.
3.2 RELATIONSHIPS
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DIVERSITY & TROPHIC EFFECTS
Predation can have far-reaching effects on biological communities. For example, a sea star is the top
predator upon a community of invertebrates inhabiting rock pools in the Pacific Northwest. The rest of
the community included molluscs, barnacles and other invertebrates for a total of 12 species. When an
investigator removed all the sea stars from the community, an acorn barnacle and a mussel began to
occupy virtually all the available space out-competing other species. Species diversity dropped from 12
species to, essentially, just 2. The sea star was a keystone predator, keeping the strongest competitors
in check. Although it was a predator, it also helped maintain diversity in the community.
When non-native species (“exotics”) invade an area, they often create a domino effect, causing many
other species to increase or decrease. For example, the rainbow trout was purposely spread to virtually
all parts of the world where it could survive and be harvested as a valuable food fish. In New Zealand,
however, the trout has out-competed native fishes, which are now found only above waterfalls that act as
barriers to trout dispersal. As the trout is a more effective predator than the native fish species, the
invertebrates that are prey to the trout are reduced in abundance wherever the trout are found. In turn,
algae, which are grazed by the invertebrates, also increase because of reduced grazing pressure. This
domino effect is an example of a trophic cascade and its effects can be very difficult to counteract or
correct.
3.2 RELATIONSHIPS
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MORE EFFECTIVE PREDATORS & MORE EVASIVE PREY
Natural selection tends to favour more effective predators and more evasive prey. Easily captured prey
are eliminated while prey with effective defences that are rapidly inherited start to dominate the
population. Evolutionary "arms races" have been recorded in many predator-prey relationships including
for example, certain snails, which become more heavily armoured over time while their predators, crabs,
develop more massive claws with greater crushing power.
REFERENCES & FURTHER READING
http://www.globalchange.umich.edu/globalchange1/current/lectures/predation/predation.html
3.2 RELATIONSHIPS
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3.2.4 Symbiosis
The term “symbiosis” defines a close and often long-term association between different biological
species. The symbiotic relationship may be further categorized as mutualistic or commensal. Mutualism
describes any relationship between individuals of different species where both individuals derive a
benefit. In contrast, commensalism describes a relationship between two living organisms where one
benefits and the other is not significantly harmed or helped. Symbiotic relationships included those
associations in which one organisms lives on another (ectosymbiosis, such as mistletoe), or where one
partner lives inside another (endosymbiosis, such as certain bacteria in humans or zooxanthellae in
corals). Symbiotic relationships may be obligate (necessary to the survival of at least one of the
organisms involved) or facultative (where the relationship is beneficial but not essential to survival of the
organisms). There are many examples of symbiotic relationships in the ocean including the following:
1. Clownfish / Sea Anemone
One example of mutual symbiosis is the relationship between clownfish that dwell among the tentacles of
sea anemones. The territorial clownfish protects the anemone by threatening and chasing away
anemone-eating fish. In turn, the stinging tentacles of the anemone protect the clownfish from its
predators (clownfish are coated with mucus that protects it from the sea anemone’s stinging tentacles).
3.2 RELATIONSHIPS
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2. Cleaner Fish & Shrimp / Larger Fish
Several species of cleaner fish and cleaner shrimp are found on coral reefs. These animals can be seen
advertising their presence to larger fish by hovering in midwater and offering their cleaning services.
They keep other fish clean and healthy by removing bits of dead or infected skin as well as skin parasites
and fungi. In return, they obtain food and immunity from being eaten by the larger fishes.
3. Corals / Zooxanthellae
Coral polyps form a symbiotic relationship with algae called zooxanthellae. Zooxanthellae are
endosymbionts because they are symbionts (organisms that are part of a symbiotic relationship) that live
inside (endo) the body of the coral. Zooxanthellae have both animal & plant features but are usually
considered to be algae since they are able to utilize energy from sunlight and use it to convert carbon
dioxide and water into oxygen and sugars (photosynthesis). When many zooxanthellae live within a coral
polyp, they provide the polyp with extra food and oxygen from their photosynthesis, which the polyp uses
to build its skeleton. In exchange, zooxanthellae are given a protected place to live and carbon dioxide
from the coral polyp’s respiration. Different zooxanthellae live with different types of corals and come in
many different forms and colors. It is the zooxanthellae that give corals their beautiful colors. When
corals are stressed, they eject their zooxanthellae, making them look white or bleached; this condition is
known as "coral bleaching".
3.2 RELATIONSHIPS
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4. Lichen – Fungus & Alga / Blue Green Bacterium
A lichen is not a single organism but is the result of two or more separate organisms living permanently
together. All lichens are made up of a fungus partner and an alga or cyanobacterium partner, or both.
Lichens can be many colors (e.g. green, grey, orange and yellow) and can take many intricate shapes
and forms.
REFERENCES & FURTHER READING
http://en.wikipedia.org/wiki/Symbiosis
http://www.snh.org.uk/publications/on-line/NaturallyScottish/lichens/whatislichens.asp - Lichen
http://www.earthlife.net/lichens/lichen.html - Lichen
3.3 ECOSYSTEMS & HABITATS
3.3 ECOSYSTEMS & HABITATS
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3.3 ECOSYSTEMS & HABITATS
3.3 ECOSYSTEMS & HABITATS
3.3.1 Patchy, Uneven Living Spaces
The ocean is three-dimensional, offering vast living space and
diverse habitats from the surface through the water column to the
seafloor. Most of the living space on Earth is in the ocean.
However, this living space is “uneven”. Certain parts of the ocean
are more hostile and difficult to live in than others.
Ocean habitats are defined by environmental factors. As a result of
interactions between abiotic (i.e. non-living) factors such as salinity,
temperature, oxygen, pH, light, nutrients, pressure, substrate and
circulation, ocean life is not evenly distributed temporally or spatially.
In other words, it is “patchy”.
For example, parts of the ocean experience seasonal blooms of
plankton. This is a time of abundance for predators. However, this
period of abundance is only temporary and, for the rest of the year,
pickings are much leaner. In order to survive, predators must adapt
by changing their diet or migrating to find other prey.
Some regions of the ocean, such as coral reefs, support more
diverse and abundant life than anywhere on Earth while much of the
open ocean is considered a desert.
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Ocean Literacy Principle 5(e)
The ocean is three-dimensional,
offering vast living space and
diverse habitats from the surface
through the water column to the
seafloor. Most of the living space on
Earth is in the ocean.
Ocean Literacy Principle 5(f)
Ocean habitats are defined by
environmental factors. Due to
interactions of abiotic factors such
as salinity, temperature, oxygen,
pH, light, nutrients, pressure,
substrate and circulation, ocean life
is not evenly distributed temporally
or spatially, i.e., it is “patchy”. Some
regions of the ocean support more
diverse and abundant life than
anywhere on Earth, while much of
the ocean is considered a desert.
3.3 ECOSYSTEMS & HABITATS
ECOSYSTEMS
An ecosystem consists of all the living organisms and the non-living
things within a specific area. For example, a sandy beach
ecosystem consists of all the animals and plants, plus the physical
features, such as the sand and the sea.
ENVIRONMENT AFFECT ORGANISMS
There are many different types of marine ecosystems, such as rocky
beaches, sandy beaches, estuaries, mangroves, coral reefs and
kelp forests.
In order to fully understand a marine environment, it is important to
know not just the biological and behavioural interrelationships
between different animals that live in an area but also the physical
conditions affecting the environment since both affect an organism’s
ability to survive.
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Interesting!
In 3-dimensional space, there are 6
degrees of freedom – up, down,
left, right, forward and backward.
Humans are used to moving left
and right, and forwards and
backwards but are less used to
moving up and down. In the ocean,
moving up and down in the water
column is highly important.
3.3 ECOSYSTEMS & HABITATS – OCEAN HABITATS
3.3.2 Ocean Habitats & Environments
The ocean can be divided into a set of habitats or environments
(often referred to as ‘eco-regions”) in which life can survive. These
are outlined below and are discussed in more detail later.
1. COASTS
One of the most difficult habitats in which to live is along the coasts.
Tides, waves and predation cause vertical zonation patterns along
the shore, influencing the distribution and diversity of organisms.
Different life lives in the different environments such as rocky coasts,
sandy coasts, and estuaries, with estuaries providing important and
productive nursery areas for many marine and aquatic species.
2. TROPICAL SEAS
Tropical seas are found between the Tropic of Cancer and the
Tropic of Capricorn. Several key environments are found in tropical
seas.
Mangroves, sea grass beds and coral reefs provide
environments for a wide variety of life.
3. TEMPERATE SEAS
Temperate seas lie between the tropics and the polar regions.
These are cool green waters that are immensely rich in algae, plant,
and animal life.
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Ocean Literacy Principle 5(g)
There are deep ocean ecosystems
that are independent of energy from
sunlight and photosynthetic
organisms. Hydrothermal vents,
submarine hot springs, methane
cold seeps, and whale falls rely only
on chemical energy and
chemosynthetic organisms to
support life.
Ocean Literacy Principle 5(h)
Tides, waves and predation cause
vertical zonation patterns along the
shore, influencing the distribution
and diversity of organisms.
Ocean Literacy Principle 5(i)
Estuaries provide important and
productive nursery areas for many
marine and aquatic species.
3.3 ECOSYSTEMS & HABITATS – OCEAN HABITATS
4. POLAR SEAS
The polar seas and regions may be frozen wastelands in many
areas but there is also a great deal of contrast and variation in the
conditions, and life can and does exist in both the Arctic and
Antarctic. In the frozen seas, invertebrates, fish, sea birds and sea
mammals abound.
5. OPEN OCEAN
The open ocean is a virtual desert and, yet, life does live and flourish
here. Many open ocean organisms migrate daily from the relative
safety of the depths of the ocean to the surface to feed at night
before returning to the depths before daylight while other open
ocean animals will cross vast tracts of the open ocean in search of
food and mates.
6. DEEP OCEAN
In the ocean trenches and deep ocean, there is no sunlight. In spite
of this, there are still deep ocean ecosystems that are independent
of energy from sunlight and photosynthetic organisms. Life,
including crabs and worms, can live in the deep, dark depths, and
survive the searing heat from hydrothermal vents or cold methane
seeps, relying solely on chemical energy and chemosynthetic
organisms for life. The carcasses of dead whales and other animals
that have fallen to the bottom of the ocean also serve to supply food
to deep ocean animals, such as hagfishes and deep water sharks.
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3.4 ACTIVITIES
3.4 ACTIVITIES
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3.4 ACTIVITIES
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3.4 ACTIVITIES
3.4.1 Origin Of Life
CORE ACTIVITY
(a) Divide the class into three groups to draw a series of posters about early Earth during the
Precambrian eon and is composed of the following eras: Hadean, Archaean and Proterozoic. Assign an
era to each group for investigation using books or the Web. For example, please see:
http://www.ucmp.berkeley.edu/help/timeform.html
http://www.fossils-facts-and-finds.com/geologic_time_line.html
Create a poster for each era, consisting of pictures, drawings and information about the era. For each
era include the following:
• Era Name & Timeline
• Environment & Climate
• Key Events
Put up all posters along the classroom wall to get an overall timeline of very early life on earth.
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3.4 ACTIVITIES
For example:
PRECAMBRIAN (4,500-543 MYA)
HADEAN
ARCHAEAN
PROTEROZOIC
Timeline
4,500-3,800 MYA
Timeline
3,800-2,500 MYA
Timeline
2,500-543 MYA
Environment
Molten lava
Volcanoes
Environment
Methane, Ammonia, Hydrogen
Toxic to life on Earth today. Water
vapour becomes liquid
Environment
Oxygen buildup due to blue-green
bacteria.
Carbon dioxide, nitrogen and ozone
levels build up.
Atmosphere’s ozone layer formed
which screened life from the effects
of the Sun’s ultraviolet radiation.
Key Events
Earth cools
Rocks form
By Team 1
Key Events
Life first appears on Earth in the
Archaean. The oldest fossils date
to roughly 3,500 MYA and consist of
blue-green bacteria. In fact, all life
on Earth for the next 1,000 million
years was probably bacterial.
By Team 2
Key Events
About
1,800
MYA,
simple
eukaryotic cells started appearing.
Multi-cellular algae and multicellular animals started appearing
By Team 3
3.4 ACTIVITIES
3.4.2 Ocean Life
CORE ACTIVITY
(a) Make a diorama of ocean life.
For instructions on constructing a diorama and for templates, please see:
http://www.enchantedlearning.com/crafts/Oceandiorama.shtml
http://h10025.www1.hp.com/ewfrf-JAVA/actCtrImg/c00457704.pdf
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3.4 ACTIVITIES
Include as many of the following organisms in the diorama as you can:
Algae – e.g. kelp
Plants – e.g. sea grasses
Animals
Vertebrates (animals with backbones):
Fish – e.g. angelfish, groupers, sharks and rays
Reptiles – e.g. sea turtles, sea snakes
Birds – e.g. puffins, penguins, gulls
Mammals – e.g. sea otters, seals, sea lions, walruses, whales, dolphins, manatees
Invertebrates (animals without backbones):
Cnidarians – e.g. corals, jellyfish
Porifera – e.g. sponges
Crustaceans – e.g. shrimps, crabs, lobsters, barnacles
Molluscs – e.g. clams, cockles, mussels, oysters, octopus, squid
Echinoderms – e.g. sea stars, sea urchins, sand dollars, sea cucumbers
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3.4 ACTIVITIES
3.4.3 Classification
EXTENDED ACTIVITY
(a) Use the Web to lookup the following species:
• Whitetip reef shark (Triaenodon obesus)
• Green sea turtle (Chelonia mydas)
• Emperor penguin (Aptenodytes forsteri)
• California sea otter (Enhydra lutris)
http://en.wikipedia.org/wiki/Whitetip_reef_shark
http://en.wikipedia.org/wiki/Green_sea_turtle
http://en.wikipedia.org/wiki/Emperor_Penguin
http://en.wikipedia.org/wiki/Sea_Otter
Pay close attention to the similarities and differences between them. For example, what features are
common to a fish and a bird? What are some features that distinguish them from one another? These
similarities and differences allow you to classify them into various groups.
(b) What features are common to all four species?
(c) What are some whitetip reef shark features?
(d) What are some green sea turtle features?
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3.4 ACTIVITIES
(e) What are some emperor penguin features?
(f) What are some California sea otter features?
(g) Fill out the following classification table:
Whitetip Reef Shark
Kingdom
Phylum
Class
Order
Family
Genus
Species
Green Sea Turtle
Emperor Penguin
California Sea Otter
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3.4 ACTIVITIES
ANSWERS
(a) Use the Web to lookup the following species:
• Whitetip reef shark (Triaenodon obesus)
• Green sea turtle (Chelonia mydas)
• Emperor penguin (Aptenodytes forsteri)
• California sea otter (Enhydra lutris)
http://en.wikipedia.org/wiki/Whitetip_reef_shark
http://en.wikipedia.org/wiki/Green_sea_turtle
http://en.wikipedia.org/wiki/Emperor_Penguin
http://en.wikipedia.org/wiki/Sea_Otter
Pay close attention to the similarities and differences between them. For example, what features are
common to a fish and a bird? What are some features that distinguish them from one another? These
similarities and differences allow you to classify them into various groups.
(b) What features are common to all four species?
They are all animals (Animalia)
They all have a backbone (Chordata)
(c) What are some whitetip reef shark features?
It is a cartilaginous fish (Chondrichthyes)
As a fish, it has gills and is able to breathe in the water
It has a body made of cartilage
3.4 ACTIVITIES
(d) What are some green sea turtle features?
It is a reptile (Reptilia)
It is cold-blooded (or poikilothermic)
It lays eggs and buries them in the sand to keep them warm
(e) What are some emperor penguin features?
It is a bird (Aves)
It is warm-blooded (or homeothermic)
It has feathers and a bill or beak
It lays eggs and incubates the eggs to keep them warm
(f) What are some California sea otter features?
It is a mammal (Mammalia)
It is warm-blooded (or homeothermic)
It gives birth to live young
It has fur and feeds its young on milk
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3.4 ACTIVITIES
(g) Fill out the following classification table:
Whitetip Reef Shark
Green Sea Turtle
Emperor Penguin
California Sea Otter
Kingdom
Animalia
Animalia
Animalia
Animalia
Phylum
Chordata
Chordata
Chordata
Chordata
Class
Chondrichthyes
Reptilia
Aves
Mammalia
Order
Carcharhiniformes
Testudines
Sphenisciformes
Carnivora
Family
Carcharhinidae
Cheloniidae
Spheniscidae
Mustelidae
Genus
Triaenodon
Chelonia
Aptenodytes
Enhydra
Species
Obesus
mydas
forsteri
lutris
3.4 ACTIVITIES
3.4.4 Adaptation
CORE ACTIVITY
(a) Study the following drawings of different teeth, jaws, and mouths of various fishes.
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3.4 ACTIVITIES
(b) What does a parrotfish eat? Why are their teeth and jaws well-adapted to what they eat?
(c) What does a moray eel eat? Why are their teeth and jaws well-adapted to what they eat?
(d) What does a butterflyfish eat? Why are their teeth and jaws well-adapted to what they eat?
(e) Why is a moray eel not adapted to eating corals?
(f) Why is a butterflyfish not adapted to eating other fish?
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3.4 ACTIVITIES
ANSWERS
(a) Study the following drawings of different teeth, jaws, and mouths of various fishes.
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3.4 ACTIVITIES
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(b) What does a parrotfish eat? Why are their teeth and jaws well-adapted to what they eat?
The parrotfish has a parrot-like “beak” from fused teeth and strong jaws to help it bite into rock-hard coral
structures and scrape off the algae and corals.
(c) What does a moray eel eat? Why are their teeth and jaws well-adapted to what they eat?
Morays eels are predators that feed on fishes, octopuses, crustaceans and molluscs. They have long,
sharp teeth and powerful jaws that can crush bone.
(d) What does a butterflyfish eat? Why are their teeth and jaws well-adapted to what they eat?
The foureye butterflyfish have long, pointed mouths for plucking out coral polyps as food. They feed
mainly on hard and soft corals (gorgonians), polychaete worms, and tunicates.
(e) Why is a moray eel not adapted to eating corals?
A moray eel does not have a long, pointed mouth for plucking out coral polyps.
(f) Why is a butterflyfish not adapted to eating other fish?
A butterflyfish does not have the long, sharp teeth or powerful jaws needed to hunt and kill other fish.
3.4 ACTIVITIES
3.4.5 Food Pyramid
CORE ACTIVITY
(a) Arrange the following organisms in a food pyramid
• Plants
• Whale sharks
• Blue whales
• Great white sharks
• Phytoplankton
• Zooplankton
• Sea urchins
• Seals
• Killer whales
• Algae
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3.4 ACTIVITIES
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3.4 ACTIVITIES
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(b) Imagine a blue whale has taken in a mouthful of seawater. What kind of things might be in its mouth?
In contrast, what might be in a killer whale’s mouth?
(c) Where would you put a human in the food pyramid? Why?
(d) Discuss whether you think humans can be considered to be top predators
3.4 ACTIVITIES
ANSWERS
(a) Arrange the following organisms in a food pyramid
• Plants
• Whale sharks
• Blue whales
• Great white sharks
• Phytoplankton
• Zooplankton
• Sea urchins
• Seals
• Killer whales
• Algae
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3.4 ACTIVITIES
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3.4 ACTIVITIES
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(b) Imagine a blue whale has taken in a mouthful of seawater. What kind of things might be in its mouth?
In contrast, what might be in a killer whale’s mouth?
Blue whales eat plankton by filtering it from mouthfuls of water. Killer whales are predators and feed on
many things including seals, fish and squid.
(c) Where would you put a human in the food pyramid? Why?
Humans would probably be considered secondary or tertiary consumers although it can be argued that
because we hunt and eat many things, we should be at the top of the food pyramid and be considered a
quaternary consumer.
(d) Discuss whether you think humans can be considered to be top predators
Humans are a little strange because in some ways we are very much a top predator but in other ways we
do not fit the bill at all. We may be considered to be a top predator since we eat many other animals and
we are rarely preyed upon. However, humans are probably not true top predators in the sense that we
do not have the teeth or predatory abilities other top predators (e.g. sharks, lions, tigers) have. We also
routinely have a mixed animal and vegetable (omnivorous) diet in contrast to most top predators which
are carnivorous. We are also very numerous compared to other top predators.
3.4 ACTIVITIES
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3.4.6 Predator-Prey
CORE ACTIVITY
(a) Draw a line between the predators on the left with their prey on the right to illustrate their predatorprey relationship.
3.4 ACTIVITIES
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(b) One of the animals does not prey on other animals but is a herbivore (an animal that eats plants).
Which is it?
(c) If a shark eats a tuna, and a tuna eats other fish, which is a predator and which is prey?
3.4 ACTIVITIES
66
ANSWERS
(a) Draw a line between the predators on the left with their prey on the right to illustrate their predatorprey relationship.
3.4 ACTIVITIES
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3.4 ACTIVITIES
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(b) One of the animals does not prey on other animals but is a herbivore (an animal that eats plants).
Which is it?
The herbivore is the manatee which eats sea grass
(c) If a shark eats a tuna, and a tuna eats other fish, which is a predator and which is prey?
An animal can be both predator and prey. A tuna that eats other fish is a predator. However, the tuna is
also prey to sharks. Some sharks prey on other sharks so sharks can be both predator and prey.
Predators that are not consumed by any other animal (such as Great White Sharks) are known as “top
predators”.
3.4 ACTIVITIES
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3.4.7 Ocean Living Spaces
CORE ACTIVITY
(a) The ocean is a vast 3-dimensional living space. Where do the following animals live in different parts
of the water column?
• Sponges
• Whale sharks
• Sea turtles
• Corals
• Whales
• Sea otters
• Humans
• Groupers
• Flounders
• Crabs
• Zooplankton
Hint: First place the four air-breathing animals at sea-level. Then, find and label the four animals that live
on the sea floor. Finally, place the animals that live in the water in the top layer of the ocean.
3.4 ACTIVITIES
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3.4 ACTIVITIES
(b) There are 3 dimensions and 6 degrees of freedom? What are those degrees of freedom?
(c) Which animals move up and down the water column on a daily basis?
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ANSWERS
(a) The ocean is a vast 3-dimensional living space. Where do the following animals live in different parts
of the water column?
• Sponges
• Whale sharks
• Sea turtles
• Corals
• Whales
• Sea otters
• Humans
• Groupers
• Flounders
• Crabs
• Zooplankton
Hint: First place the four air-breathing animals at sea-level. Then, find and label the four animals that live
on the sea floor. Finally, place the animals that live in the water in the top layer of the ocean.
3.4 ACTIVITIES
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Note there are several possible solutions and it doesn’t really matter whether corals and sponges are
reversed for example. What is important is that you would typically see them on the sea floor.
(b) There are 3 dimensions and 6 degrees of freedom? What are those degrees of freedom?
The 6 degrees of freedom are up, down, left, right, forward and backward.
(c) Which animals move up and down the water column on a daily basis?
Zooplankton moves up and down the water column. Many fishes and other animals that eat zooplankton
follow their daily movement up and down the water column.