Download The Sea and the Ecosystem

___________________ _____Educational Kit Mr.Goodfish Campaign - Module 1 - Page 9
MODULE 1
“THE SEA AS AN ECOSYSTEM”
____________________________________________________________
TEACHER’S GUIDE
Module map
Topics
Life in marine environment: organisms, habitats and ecosystems.
Trophic chains and networks: trophic relationships among marine organisms.
Life cycles.
Aims and rationale
To understand how marine organisms are deeply related to the environment and to each other.
Instilling values for the sharing of sealife resources.
Let the student reflect upon the environmental balance issue.
Inserts
1. Plankton, nekton and benthos.
2. From the food chains to the trophic networks.
3. The organisms life cycles.
Subjects
Marine biology, zoology, botany, ecology.
Fact sheets
Type
Title
Activities
S - Survey
1. “A sea of life”
Survey in class.
2. “Marine environments”
3. “Marine environments”
4. “Marine environments”
R - Research
5. “Marine environments”
8. “Watch out for the mouth”
Visits of a public
11. “The identikit”
Aquarium.
6. “Where do they live?”
7. “The 4 cards game”
E - Experience/elaboration
9. “One chain thrieves another one”
10. “Chains or networks?”
12. “Life is a ring-a-ring-a-roses”
13. “Draw an ecosystem”
14. “Build up your network”
T - Test
Survey in class.
15. “Invent a story”
Link to Mr.Goodfish Campaign issues
Learning the base concepts on organisms, their habitats and delicate ecological balances.
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Didactic instructions
In order to develop the educational project
“Mr.Goodfish", we reckon it is important to
start with the comprehension of the
“ecosystem” concept, which can be
described as the complex of all the living
organisms inhabiting a certain physicalchemical environment, and the mutual
relationships existing among them and
between them and their environment. Every
ecosystem also has the capability of keeping
a dynamic balance in time, through the
continuous matter and energy exchange.
It is through the knowledge of these aspects
that the basis are built to deal and
understand the following forms’ topics,
dedicated to the exploitation of the seafood
resources, and the related effects on the
marine ecosystem.
However, when talking about the ecosystem,
we think it is appropriate to introduce the
adaptation concept.
In an organism, every structure and behaviour
fulfil a specific task, and they have been
“shaped” by the evolution processes, in
order to respond in the most effective way to
the environmental stimulations.
We can hardly imagine a tranquil survival for
a clam in the open ocean, for example, or for
a swordfish among the rock pools.
Every organ of each living being represents
then a precise and efficient adaptive solution
to perform the various vital functions, i.e.
locomotion, nutrition and reproduction.
These are the objects of the study of the “sea
ecosystem” of this first form, regardless of
the references correlated to the systematic
classification of the different organisms.
More specifically, the following subjects are
considered in this form:
- marine organisms and environments;
- trophic chains and networks;
- life cycles.
A limitation of this work is certainly
represented by the required abstraction
complexity, somehow stemming from the
difficulty encountered in studying the
organisms and the marine ecosystems in situ.
For this reason, we suggest performing some
activities of this form (in particular cards “R”
and “E”), making use of the representations
in artificial tanks at an Aquarium, for the
observation of the organisms and their
habitats, bearing in mind the conceptual
limitation which the tanks’ modelling entails,
not only for the children, but for the adults
too.
The visit to a great public Aquarium also has
the advantage of stimulating, developing and
verifying the children observation and
deduction capabilities.
The work starts with fact sheet S 1,
1, which
pose some general questions in order to
obtain a full picture of the previous
knowledge and on the students’ perception
of the marine environment and the organisms
which live in it.
Fact sheet R 2-3-4-5 and E 6-7 in particular,
are dedicated to the theme “marine
organisms and environments”.
environments”. In order to
take some cues as to plan the work on this
subject, we recommend reading the insert 1,
1
dedicated to the great categories of marine
animals (plankton, nekton and benthos) and
to the main environments (pelagic and
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benthic).
Fact sheet R 2-3-4-5 aims at helping the
students to develop in a direct way, through
observation and research, the relationships
between the physical characteristics of the
different marine environments and the shape,
the movements and the colour of the animals
that inhabit them. The main environments of
the Mediterranean Sea are taken into
consideration: pelagic and benthic (rocky
bottoms, mobile bottoms and the posidonia
meadows).
The students are therefore asked to observe
all the components present in an
environment and to pay attention particularly
to the precise location of the different
animals and vegetables, or of the other
environment elements which are the object
of the study.
Fact sheet E 6-7 suggests the revision and
elaboration of what has been learnt in card 2.
The suggested experience draws the
students
attention
to
the
different
mechanisms that marine organisms employ
for movement, with the aim of inducing the
students to formulate some hypotheses on
such
locomotion
adaptations,
and
consequently, on the habitats of the various
animals.
Once back in the classroom, fact sheet T 13
13
enables the verification of the learning
abilities, memory and abstraction level of the
students, through the graphic visualization of
the various ecosystems (and of their
components).
The students are also asked to hypothesize
the role which each element takes on within a
certain context, testing at the same time their
intuition abilities.
For the sake of completeness, we also invite
you to allocate the reproduction of all types
of observed environments, and also to
stimulate the comparison among the
documentation, and the debate among the
students.
The learning of these concepts,
correlated to the marine environments, is
important and fundamental, in order to
be able to tackle the form dedicated to
the fishing techniques in the various
environments,
and
therefore
to
understand how and where the seafood
resources ending up on our dinner tables
are taken.
Starting from the marine organisms in
their environment, one can also mention
the biodiversity concept, taking into
account that generally speaking, the
lower the degree of an environment
biodiversity, the more that environment is
in a poor state of “health”. In fact, the
environments tendency to host an ever
decreasing number of species, caused by
the introduction of polluting elements, or
by man’s negative actions, has to be
interpreted
as
an
environmental
degradation phenomenon.
Let’s now take into consideration the topic
“trophic chains and network
networks”
works”,
s” to which
insert 2 is dedicated.
This subject allows the transition from the
study of the organisms’ relationships with
their environment, to the one of the mutual
relationships among the same organisms,
from a trophic point of view.
To this end, the feeding topic in fact sheet R
8 is the first one to be tackled. In this card,
like in the previous ones, the student is asked
to focus the attention on the organisms in the
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tanks, and particularly on the shape of the
animals’ mouth. The aim of this first task is
clearly to let the students understand the
differences among the various mouth
apparatuses, and to let more specific aspects
of these structures come to light.
With fact sheet E 99-10,
10, the student is invited
to elaborate what has just been learnt, to
build some simple food chains and trophic
networks.
The first fact sheet focuses on some food
chains, which the students will have to
complete with the missing links, whereas the
second one let the students free to choose
an animal (which will be placed in the middle)
and to create around it the pertaining food
chain. The students are therefore led
gradually to elaborate the concept of trophic
net, through the critical analysis of the mutual
relationships among the organisms.
Obviously, it is not guaranteed that the
student will spot correctly the elements of the
food chain and/or trophic net: it will be case
then of discussing the errors and drawing the
right conclusions. In this sense, it could prove
interesting to raise a debate in the classroom,
where every student would have to justify
his/her answers, in order to come to the right
conclusions, and highlighting the students
different points of view: often, in spite of the
common choice of an animal by several
students, the chain elements mentioned by
each one prove to be different.
Finally, with fact sheet T 14, we ask the
students to build some trophic nets of coastal
environments (rocky, sandy, posidonia
meadows, for example) and pelagic (divided
among the students), making then possible
the link with the study of the different marine
environments. A confrontation “in teams" will
follow, according to the environmental type,
where the students of each team will realize,
starting from each document, a graphic
representation to illustrate in the most
complete way, the trophic relationships
among the organisms of the chosen
environment.
The study of the trophic nets let us
understand how each element has its
defined role, creating a complex system
of relationships with the others. The
assimilation
of
this
concept
is
fundamentally important, in order to
tackle topics such as fishing and
aquaculture, and to be able to fully
understand the repercussions on the sea
ecosystem.
The last topic of this form is dedicated to the
“organisms’ life cycles”.
cycles” We think that such a
subject is particularly important, as it is the
reproductive success which guarantees the
survival of every species,
species and therefore to
keep the ecosystems alive and balanced.
One has to start by saying that this topic is
very complex, and we will only tackle it
sideways, to understand its aspects linked to
seasonality,
environments,
migrations,
achievement of adulthood, and life span.
Insert 3 is dedicated to this subject, where as
well as general overview on the reproduction
topic, are also shown some examples of life
cycles. In particular, the life cycles of the
organisms of a pelagic food chain are shown,
to connect with insert 1 (the teacher can
obviously investigate the argument also
about other organisms).
This allows highlighting how the various
trophic levels are bound by a strong tie, and
also how some organisms belong to different
trophic levels in the various phases of the life
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cycles.
Fact sheet R 11 and E 12,
12, deal first of all with
the reproduction theme as some sort of
game: the students must discover some
organisms through the clues linked to
reproductive aspects. This work stimulates
the observation skills and curiosity, and it
allows understanding some aspects of
reproduction (i.e. sexual dimorphism, internal
and external insemination), to then tackle the
concept of life cycle.
The aim of these last two cards is to
introduce the students to the different
“biological times” of the organisms,
which necessarily have to be taken into
great consideration, within a context of
exploitation of the fish resources (tackled
in the next forms).
At the end of the subject, the verification in
fact
fact sheet T 15 is recommended; it asks to
write about an organism by choice, taking a
cue from what has been learnt so far, and
which gives at the same time free rein to
each student's imagination.
By now it should be clear how life
environment, diet and reproduction are
strictly connected and essential for the
existence of each animal.
The study of the ecosystem, leads then
to the awareness that all its elements
have a precise role, and each organism
is strictly linked to the other
components.
This work can help us think in a systemic way,
i.e. realize and relate the components of an
environment, without necessarily knowing
“its name and surname”, but being able to
consider each organism on the basis of its
function and the ecological role it plays
within the ecosystem
ecosystem.
system In this way, the student
spots the ecosystem dynamic balance,
formulating hypotheses which he/she will be
able to transfer to other contexts.
In doing so, the bases are laid for discussions
in the next forms, considering a further and
fundamental element which interacts with the
environment:
environment: Humans.
Humans.
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 14
INSERT 1
“PLANKTON, NEKTON AND BENTHOS”
There are two great domains in the sea: the
benthic one, represented by all the sea-beds,
and the pelagic one, which includes the mass
of the water above.
The benthic organisms can be classified
based on their movement ability and the type
of relationship with the sea-bed. The
organisms complex which lives inside the
substrate is called endofauna (if referring to
animal species), or endoflora (if referring to
vegetable species). The species which live on
the substrate surface form the epifauna and
the epiflora. The epifauna is also divided in
sessile,
sessile if it lives attached to the sea-bed,
sedentary if it has scarce movement abilities,
vagile,
vagile if it moves by crawling, or by means of
appendages.
The amberjack is a pelagic fish; it has a streamlined
shape, with no roughness. Its tail fin is linked to the
body by a sturdy peduncle, which allows fast and agile
manoeuvres.
A streamlined fish like the anchovy, which uses its tail
for its movements, can be suitable for a spacious
environment, which allows fast and wide moves, such as
the open sea.
The solutions adopted by the different
groups of organisms are in some cases so
similar,
that
animals
which
are
phylogenetically far apart from each other,
tend to show equivalent, morphological
characteristics (adaptive convergence).
The pelagic organisms
organisms are subdivided into
nekton,
nekton including the species able to actively
move against the stream, and plankton,
plankton a
term which groups all the species passively
transported by the currents, as they have
limited swimming capabilities or none at all.
The nekton is mainly represented by those
animals which have developed specific, more
or less fast swimming adjustments, according
to the species, living either in the open sea,
or in the vicinity of the sea-bed.
The sharks and dolphins dorsal fin is a clear example of
adaptive convergence.
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 15
The plankton is formed by vegetable
organisms (phytoplankton) and animals
(zooplankton). In the plankton, there are
species at egg, larval or adult stage, whose
dimensions can vary from less than a
thousandth of a millimetre, to over a metre.
The zooplankton animals can lead a pelagic
life throughout their existence, or only in part;
for example, a species can be planktonic
during the egg and larval stage, or as a
young individual, and then become nektonic
as an adult (i.e. anchovy).
One of the main problems the planktonic
organisms have to face is floating. Different
solutions have been adopted:
• the reduction of the specific weight is
obtained thanks to an elevated quantity of
water in the tissues, or with the presence of
oily drops or gas;
• expanded appendages with the aim of
slowing down the sinking.
• natatory movements to maintain the
hydrostatic trim.
Some zooplankton components make daily,
vertical migrations of some hundreds metres,
reaching deep waters during the day and
going back up during the night (nychtemeral
migrations).
Some plankton organisms, both animal and vegetable,
are characterised by particular expanded appendages,
capable of opposing the sinking of the water column.
Among the main factors which cause these
movements, these are worth a mention:
• the need to escape from those predators
which use their sight while hunting;
• the energy saving (by going down to colder
waters, the zooplankton uses less energies);
• the withdrawal from the ultraviolet rays;
• the transfer to superficial waters, differing
from the original ones (the deep waters have
a speed and direction different from the
superficial currents).
Whereas the pelagic domain is characterised
by certain uniformity, the benthic one
presents a noticeable variety of aspects in
relation to the type of substrate.
There are two main types of sea-beds:
- mobile
- rocky
All the sea-beds formed by unconsolidated
sediments are called ”mobile
mobile seasea-beds”.
beds The
benthic organisms which live there are
strongly conditioned, and suited for the
substrate’s unsteadiness, as well as the
possibility of subsiding inside it.
The
settlements of these environments vary with
different
factors,
such
as
depth,
granulometry,
sedimentation
rates,
hydrodynamic, and the steadiness of the
physical-chemical parameters.
The typical inhabitants of such sea-beds in
general are the benthic fishes, typically flat
(skates, soles, rays, stingrays), starfishes,
Cerianthus spp, bivalve molluscs and sea
snails, sea worms and shrimps.
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 16
The flat shape and the colouring of the skate, strongly
remind of the look of the sandy sea-bed; the skate’s
particular type of mimicry, suggests why this animal
tends to move very little.
These sea-beds, in the vicinity of the coast
and up to where there is enough light for the
vegetables, are often characterised by the
presence of marine pharenogams meadows
which, thanks to their root systems, are able
to anchor to the loose sea-bed (contrary to
the algae). An example is represented by the
marine pharenogams meadows formed by
the Posidonia oceanica.
The “Posidonia oceanica meadows”, form a
very well characterised ecosystem, and one of
the most productive and extended
environments of the Mediterranean Sea
coastal strip. The Posidonia oceanica, it has
to be said, is not a seaweed, but a superior
plant, with roots, stalk (rhizome) leaves,
flowers and fruits (called sea balls). It can live
up to a 30-40 metres’ depth, and the
progenitor of this plant used to live on the
emergent land.
Posidonia’s own characteristics, its growth
dynamic and the great quantity of produced
biomass, represent elements capable of
homing very diversified communities of
animals and vegetables. There are epiphyte
communities of algae and bryozoans which
settle on the leaf surface and the plant's
rhizomes, and communities of sessile, benthic
animals, such as sponges, sea worms, bivalve
molluscs, and vagiles, such as shellfishes,
starfishes, holothurians, sea urchins, sea snails
and many fishes such as sea-breams, wrasses,
pipefishes and sea-horses.
During its evolution, the sea-horse has taken on a
vertical “position”, with the subsequent pelvic and
caudal fins’ loss, in favour of a prehensile tail, which it
uses to cling to the Posidonia leaf strips. It moves
forward thanks to the fast vibrations of the dorsal fin,
whereas the vibration of the pectoral ones and the tail
movements are needed for the vertical movements.
The posidonia meadows are also used for
egg laying and nursery (increase of the young
ones) of the species which inhabit it or visit it.
One can say that the ecological role of the
posidonia can be compared to the one of the
woods and forest on land.
The "rocky
"rocky seasea-beds”,
beds” as opposed to the
mobile ones, are consolidated. The benthic
organisms which populate them are
conditioned by the mineralogical nature, and
the presence of niches and recesses in which
to hide. Also in this case, the settlements vary
according
to
depth,
hydrodynamic,
sedimentation and the environment physicalchemical parameters.
The communities which develop on the hard
sea-beds are extremely more complex, unlike
those of the mobile sea-beds; this is due to
the microclimates which are created in a very
small space (for example on the opposite
sides of the same rock).
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 17
Generally speaking, these environments are
dominated by algae, sessile and encrusting
animals like corals, sea anemones, sponges,
bivalve molluscs and sea snails, sea worms,
sea-urchins, crabs, lobsters, shrimps, together
with benthic fishes like groupers, ray’s
breams, scorpion fishes, gobies, blennies.
In particular, with the depth increase, and the
subsequent light decrease, also the algal
settlements decrease, in favour of the
animals’.
A benthic shell fish like the crab has a series of clawlike, articulated paws; these organs are shaped for
shifting on the sea-bed.
In fishes inhabiting rocky coasts, such as the Swallowtail
seaperch, the body shape tends to a generally oval or
elliptical morphology. The well developed tail fin, with
soft rays, allows a supple and adjustable push; the
dorsal and side fins are generally very well-built
(whereas the side ones are much smaller in the great
swimmers), and allow precise moves, in order to get
into narrow openings, and in case of escape,
"zigzagging" among the sea-bed rocks.
Finally, it has to be said that the benthic
communities’ structure and functioning
in general, are obviously not just linked
to the environmental parameters, but
also to biological interactions among the
organisms themselves.
Therefore, the organisms’ distribution is
linked to a complex relationships
network, whose balance is the pivot of
the functioning of the ecosystems in their
entirety.
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 18
INSERT 2
“FROM THE FOOD CHAINS TO THE TROPHIC NETWORKS”
All organisms need energy and substances to
live. The autotrophic organisms are capable
of using either light energy or chemical
energy of certain inorganic compounds and
turn it into new chemical bindings: they then
transform simple and not very energetic
molecules into complex molecules.
Animals, fungi, and nearly all bacterias are
heterotrophic instead. They must assimilate
already
energetic
complexes
(sugars,
proteins, fats, etc.).
The autotroph organisms are therefore called
producers, whereas the heterotrophs are the
consumers.
Within a community, energy and matter are
transferred from the producers to the various
levels of consumers. A food chain is then
established, formed by different trophic
levels (producers, herbivores, carnivores of a
different order).
In the ecosystems, a fundamental role is
played by the decomposing and scavenger
organisms.
The decomposers are fungi and bacterias,
which attack the dead or lifeless organic
matter, and they completely downgrade
them, exploiting their residual energy
through various steps. This process is very
slow, mostly for those resistant and difficult to
digest substances like lignin, cellulose,
animals' skeletons, etc. Because of this, the
action of the scavengers is decisive; these are
small animals who feed on the dead organic
matter, making it more accessible for the
decomposers. However, the scavengers do
not have the enzymes necessary to digest the
resistant matters: for them the remains have a
low nutritional value, and the major energy
source comes from fungi and bacterias, which
are ingested together with the remains. The
scavengers depend on the indirect
contribution of nutritious substances from the
system based on the primary producers.
Scavengers and decomposers have, in their
turn, some carnivorous predators. Therefore
there are two systems within a community:
the grazers’ and the decomposers’ systems
are linked. At the end of each cycle, the
organic matter is always reduced to simple
inorganic molecules (water, carbon dioxide,
mineral salts), i.e. remineralized.
Between levels the mass increases,
increases, but
the number of the different species
individuals decreases.
decreases
In terms of quantity for example, there
are more anchovies than tuna fishes,
and it is important to bear in mind that
the abundance of a species is decisive
for the survival of others, even if very far
apart in the trophic chain.
However, the energy has a different end:
whereas the matter is recycled, returning to
the producers in an inorganic form, the
energy is gradually dissipated (for regular
vital
functions
such
as
breathing,
reproduction, heath production, etc.) and it
decreases with every passage, resulting in the
end completely dispersed. Therefore, there
are a matter cycle, and an energy flow
(energy pyramid).
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 19
Some water physical properties significantly
influence the marine trophic structure. Water
absorbs light, decreasing its intensity with the
depth increase.
As the vegetables need a certain luminous
intensity for the photosynthesis to take place,
they can only live in the more shallow sea
water. In the crystal clear waters of the
Tropical Seas, the maximum depth for the
photosynthesis is around 120/130 metres
deep, but it can be reduced to a few metres
in the coastal, murky waters This depth is
marked by the euphotic zone; underneath it
there is still enough light to see, but not to
photosynthesize: the disphotic zone, which
reaches the 500/800 metres. Finally, there is
the aphotic zone, perpetually in the dark. The
euphotic zone of the coastal areas, where
algae and benthic plants grow (anchored to
the sea bed), amounts to a small percentage,
Simple examples of trophic chains
and energy pyramid.
© Laurent AUDOUIN
if compared with the total volume of the
oceans.
The sea primary production relies basically on
the unicellular algae, which live hanging in
the water column, i.e. the phytoplankton,
which produces more than 90% of the whole
organic matter.
Generally speaking, we can say that the
marine food chains have more trophic
levels which separate the producers
from the top predators,
predators compared to
what happens on land. Marine primary
producers (planktonic unicellular algae)
have in fact a smaller size compared to
the land ones, giving a feeding
opportunity to a great quantity of
organisms,
both
herbivores
and
carnivores, which are also very small.
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 20
The quantity of available energy for the
great predators is therefore extremely
reduced, because of the elevated
number of intermediate levels to be
crossed before reaching the top of the
pyramid.
Baleen Whales (whales) and not only, on the
contrary,
filter
great
quantities
of
zooplankton, drastically reducing the number
of passages within the food chain; they can
then optimize at the most the energy transfer
from the producers up to the top of the
trophic structure.
The planktonic organisms are transported by
the sea currents and are present in the water
column in variable concentrations, according
to the season, climate and nutrients’
availability. Some zooplankton components
are capable of vertical migrations of some
hundred metres, moving to deep waters in
daytime and coming back up at night
(nychtemeral migration). This also gives the
opportunity to a great quantity of organisms
to move in different masses of water, and to
spread in currents with variable directions
and intensity. Plankton is very abundant also
in the vicinity of the coasts, where it is utilized
by the sessile animals; in this way the survival
chance is guaranteed for those organisms
which are permanently
attached to
a
substrate, and do not have the possibility to
move about looking for food.
Therefore, when analysing a real community,
the trophic relationship appears to be a lot
more complex, compared to the pure and
simple food chain model.
For example, many marine carnivores are
opportunistic scavengers; different predators
feed both on herbivores and scavengers or
other carnivores; the filter-feeders can be
potentially placed in more trophic levels, as
they eat bacteria, unicellular algae, small
organisms and organic matter particles alike.
Rather than simple chains then, it is more
appropriate to talk about trophic nets,
nets
formed by a complex interactions
system.
In every ecosystem there is a very
delicate
dynamic
balance,
which
concerns all the populations linked to the
trophic net. A variation of the
environmental characteristics could lead
to substantial alterations of the whole
ecosystem. As long as the alterations are
limited, the system manages to absorb
them. However, beyond a certain limit
irreversible upheavals can happen.
Talking about trophic nets, it is then
necessary to consider the problem
caused by the fishing activity, when it
entails picking up members of a fish
population in a quantity which is greater
than the species’ resilience. This can
cause an increase in the number of
natural prays of the over-exploited
population (which tends to disappear),
and at the same time a noticeable drop
of its predators. It can also happen that
the predators start to feed on other
species, altering in this way the
ecosystem balance.
In order not to incur irreversible
consequences, it is necessary that the
exploitation of a species is regulated
beforehand, establishing the minimum
size and quantity of the specimen which
can be captured, without altering the
natural systems balance.
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 21
Consequently,
adequate
preservation
measures must be introduced,
introduced giving a
fundamental relevance to the checks for such
regulations' observance.
We will expand on these aspects in the
following Modules dedicated to the "seafood
resources".
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 22
INSERT 3
“THE ORGANISMS LIFE CYCLES”
One of the fundamental characteristics of the
living organisms is their ability to increase
numerically, i.e. to reproduce themselves.
This characteristic is represented with
different models, according to the groups (or
systematic categories), and they have
improved in millions of years of natural
selection, with the aim of guaranteeing the
species the best success.
Here we will tackle the reproductive
strategies of the animal kingdom more in
detail, whereas we will only briefly mention
the ones adopted by the vegetables.
The animal world reproductive strategies can
be grouped into 2 great categories: sexual
reproduction
(gamic)
and
asexual
reproduction (agamic).
The sexual reproduction is the one where the
new organism is generated by cells called
gametes (eggs and sperm cells), whether
through the fusion between male and female
gametes (amphigenic reproduction), or with
the
eggs
only
(parthenogenetic
reproduction).
The amphigenic, sexual reproduction avails
itself of the advantages offered by the mixing
of the parents’ genetic heritage, resulting in
the maintenance of a high genetic mutability
of the new born; this generally represents an
advantage for the preservation of the
species, as it ensures a greater chance of
survival. However, the great genetic
mutability sometimes is not so advantageous
due to some specific
environmental
conditions which can be particularly harsh.
Some
organisms
resort
to
the
parthenogenetic reproduction. This strategy
generates individuals with a less varied
genetic heritage (only the “mother’s”), but it
is particularly suitable for such harsh and very
selective environmental conditions. This
strategy is adopted, for example by some
planktonic Crustaceans as an alternative to
the amphigenic reproduction
It is a different matter when it comes to the
species which reproduce in an asexual way,
meaning without the production of gametes.
This type of reproduction avails itself of the
aptitude of some organisms to generate
another one from a portion of their own
body; it can either be accidental or
spontaneous, and like in the case of
gemmation, several individuals can be born
from a single one (like in sponges, corals and
jellyfishes)
The asexual reproduction is often used by
organisms which are perfectly capable of
reproducing sexually.
With the sexual reproduction, in relation to
the life habits of the various species, different
types of insemination, egg laying and egg
development as well as cases of
hermaphroditism, can be observed.
If we consider fish, for example, we can say
that, as a rule, they exhibit external
fertilization of eggs. Sharks and rays
reproduce by internal fertilization instead,
with a real copulation between the two sexes;
same applies to some Crustaceans
(Decapoda), which also has copulatory
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 23
organs.
With
the
external
fertilization
the
reproductive success lies with the laying of
huge quantities of tiny eggs (i.e. a cod can lay
up to 9 millions!), with the aim of increasing
the chance of fertilization and survival of the
filial generation.
On the contrary, the species which exhibit
internal fertilization, or external with parental
care, the eggs number gradually decreases
(and the size becomes greater) until reaching
about ten, in case of viviparous sharks. In
these cases, the embryo development from
“indirect
indirect”
indirect (larval stage with subsequent
metamorphosis) becomes “direct
direct”
direct (absence
of larval stage, and young ones similar to the
adults).
This is due to the eggs size and the
consequent availability of nutritional reserves
(lecithic) for the embryo's development.
Small eggs have reduced quantities of
lecithic reserves available; therefore they
produce small larvae; on the contrary, big
eggs ensure the embryo a greater
nourishment quantity, and consequently the
chance of a greater development, resulting in
some cases in offspring already similar to the
adults.
The phenomenons of sexual inversion
(hermaphroditism
hermaphroditism)
aim
at
the
best
hermaphroditism
reproductive success. An example is given by
the fish belonging to the families of the seabreams (i.e. giltheads), serranidae (i.e.
groupers) and wrasses (i.e. rainbow wrasse).
In cases of hermaphroditism, the individuals
are born females or males, and only once
they have reached a certain size they realize
the sexual inversion, becoming respectively
males
or
females
(protogynous
or
protandrous hermaphroditism).
There are numerous examples of
reproductive
strategies,
and
they
demonstrate that there is not a winning
one; all are winners at a specific time in
the course of the species' evolutionary
path. This diversity, as a result of the
lengthy evolution process, is also a
product of the ongoing interaction
among the organisms and their living
environment.
Generally speaking, for many species there is
a reproductive season when the most
favourable conditions occur for the eggs
development, and most of all for the newnewborns’ survival.
In the sea waters of the temperate zones, the
reproductive processes are ruled by the
changes of the length of the day
(photoperiod) and correlated to the
temperature.
The nektonic animals, thanks to their active
movement ability, can shift towards the most
favourable environments for reproduction,
whereas benthic, sessile and planktonic
organisms must wait for the arrival of the
favourable conditions in their environment.
For example, many nektonic animals such as
fish, cuttlefish, squids, or some crustaceans
like the spider-crabs, tend to approach the
coast to reproduce, generally at springtime.
Along the coast, thanks to the greater
availability of plankton due to the more
elevated nutrients concentration, the food
availability for the new-borns is greater.
Furthermore, in proximity of the coast,
especially in certain seasons, water
temperatures are on average higher, and
therefore the offspring development is faster;
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 24
hence they can reach greater sizes more
quickly.
This movement capability (migration
migration)
migration is
particularly noticeable in species like tunas,
salmons, eels, mullets, sea basses and
giltheads, which can also travel remarkable
distances, to reach the reproduction sites; in
some cases, they can even move from the
fresh waters to sea, or vice versa.
Eels are the typical example of the
catadromous species; this means that after
being born in the sea, they go back to fresh
waters for the growing phase, and then
return
to the sea to reproduce.
Anandromous species are the ones like the
salmon which, on the contrary, are born in
fresh waters, grow in the sea, and go back to
fresh waters to lay the eggs.
Chosen parental cares are different: some
species, like gobies, blennies, squids,
octopuses and cuttlefish, lay and look after
the eggs, which are fixed to the rocky sea
bed; in other cases, like for many crabs, the
eggs are carried attached to the abdomen
up to hatching,
hatching in order to avoid the
scattering; or in case of the Cichlids,
Thrushes, and other fish, the eggs are placed
in nests, or kept in the mouth.
From what has been said, one can guess
the procedure, times and reproductions
environments intricacy. However, it is
clear how life follows a determined cycle,
with very delicate stages. From the
insemination, to the birth, development
and growth, achievement of sexual
maturity, and reproduction, it is all a
succession
of
phenomenons
and
balances; its knowledge is vital for a
correct and wise resources exploitation,
which represents a food source for
Mankind.
In order to better understand the meaning of
“life cycle”, as an example we report here
some marine organisms’ cycles. We relate in
particular the life cycles of the organisms
mentioned in the pelagic food chain
discussed in insert 2.
Organism: diatom, planktonic, unicellular
seaweed, it has a silica cell wall made of two
valves or thecae; the upper one is bigger and
covers the lower one.
Type of reproduction: alternating sexual and
asexual reproduction.
Insemination: external.
Reproductive season: all year round, with
spring peaks.
Reproductive environment: pelagic.
Life cycle: asexual reproduction, via diagonal
division of the cell and further reconstitution
of the smaller theca. Progressive reduction of
the cells’ dimensions blocked by the start of a
sexual
reproduction
which
originates
individuals with the original dimension, from
which the cycle resumes. During the
reproductive peaks, they can mate up to
three times a day.
Life span: weeks.
Ecological role: they represent a significant
part of the phytoplankton. The organic
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 25
molecules produced by these microscopic
algae, are one of the main sources of
nourishment for fish' larvae and zooplankton
(they represent in fact an important source of
food for marine animals just as much as
plants on terrestrial environments).
Organism: copepod, microscopic planktonic
crustacean.
Type of reproduction:
reproduction sexual.
Insemination: internal.
Development: indirect.
Reproductive season: all year round, with
spring peaks.
Reproductive environment: pelagic.
Life cycle:
cycle: insemination through copulation,
eggs laying (or their transportation in
ovigerous sacs), indirect development with a
succession of metamorphoses from one larval
stage to the next, achievement of the adult
stage, growth, reach of sexual maturity,
reproduction.
Life span: weeks.
Age of sexual maturity: from a few months to
a year.
Ecological role: they represent a significant
part of the zooplankton. They are a very
important food source for the organisms
which feed on zooplankton.
Organism: anchovy, pelagic fish.
Type of reproduction:
reproduction sexual.
Insemination: external.
Development: indirect.
Reproductive season: from April to
November.
Reproductive environment: coastal waters.
Life cycle:
cycle External insemination through the
emission of floating eggs (up to 40,000 per
female). Indirect development; larvae about 2
mm long, having a gregarious life. The larval
stage ends with the metamorphosis which
originates individuals similar to adults,
growth, achievement of sexual maturity,
reproduction.
Life span:
span More than 3 years.
Age of sexual maturity: at the end of the first
year of life (length 9 cm).
Ecological role: They are one of the most
important examples of small pelagic fish, and
they represent a very important source of
food for many fish.
Organism: mackerel, pelagic fish.
Type of reproduction:
reproduction sexual.
Insemination: external.
Development: indirect.
Reproductive season:
season end of winter to
springtime.
Educational Kit Mr.Goodfish Campaign - Module 1 - Page 26
Reproductive environment: coastal waters.
Life cycle:
cycle external insemination through the
emission of floating eggs (up to 800,000 per
female). Indirect development; larvae about 4
mm long having a gregarious life. The
metamorphosis is followed by a growth stage
and achievement of adult age, sexual
maturity and reproduction.
Life span:
span around 15 years according to the
species.
Age of sexual maturity: at the end of the
second year of life (length 18 cm).
Ecological role: very important source of
food for many great predators.
Organism: bluefin tuna, pelagic fish.
Type of reproduction:
reproduction sexual.
Insemination: external.
Development: indirect.
Reproductive season:
season mid May to mid July.
Reproductive environment: offshore waters.
Life cycle:
cycle external insemination through the
emission of floating eggs (more than 10
million
eggs
per
female).
Indirect
development; larvae about 4 mm long having
a gregarious life. The metamorphosis is
followed by a growth stage and achievement
of adult age, sexual maturity and
reproduction.
Life span:
span over 30 years.
Age of sexual maturity: between 3 and 4
years (length 95 cm).
Ecological
Ecological role: important control element of
the abundance of small pelagic fish.
Organism: viviparous shark, pelagic fish.
Type of reproduction:
reproduction sexual.
Insemination: internal.
Development: direct.
Reproductive season:
season late spring to summer.
Reproductive environment:
environment: pelagic waters.
Life cycle:
cycle internal insemination through
copulation, direct development inside the
womb (gestation period about 9 to 12
months). Birth of about 80 offspring similar to
adults, growth, achievement of reproductive
age, reproduction.
Life span:
span Between 20 to 40 years according
to the species.
Age of sexual maturity: between the fourth
and sixth year of life (length 250 cm).
Ecological role: at the top of the trophic
chain.
Finally, it is important to underline that this
analysis means to make one think about how
the different trophic levels are strictly related
also from a reproductive point of view.
Fact Sheet S 1
“A SEA OF LIFE”
Answer the following questions.
questions.
List 5 marine organisms which come into your mind at first
and, for each one,
one, mark the environment where it lives.
lives.
Organism
Where does it live?
1……………………………………………….
……………………………………………….
………………………………………………..
………………………………………………..
2……………………………………………….
……………………………………………….
………………………………………………..
………………………………………………..
3……………………………………………….
……………………………………………….
………………………………………………..
………………………………………………..
4……………………………………………….
……………………………………………….
………………………………………………..
………………………………………………..
5……………………………………………….
……………………………………………….
………………………………………………..
………………………………………………..
Could you tell the way these organisms move?
move?
1……………………………………………………………………………………………………
2……………………………………………………………………………………………………
3……………………………………………………………………………………………………
4……………………………………………………………………………………………………
5……………………………………………………………………………………………………
Could you tell what they eat?
eat?
1……………………………………………………………………………………………………
2……………………………………………………………………………………………………
3……………………………………………………………………………………………………
4……………………………………………………………………………………………………
5……………………………………………………………………………………………………
What is the difference between an animal and a vegetable
organism ?
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
Mod. 1
Fact Sheet R 2
“MARINE ENVIRONMENTS”
After observing the marine organism in the tanks,
tanks, fill
the following drawing with the correct marine
organisms inhabiting the represented environment.
environment.
How do you describe,
describe, in two words,
words, the represented
environment?
environment?
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
How do the organisms inhabiting this environment move?
move?
1…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
2…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
3…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
4…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
Can you describe their shape and body colour?
colour?
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
Mod. 1
Fact Sheet R 3
“MARINE ENVIRONMENTS”
After observing the marine organism in the tanks,
tanks, fill
the following drawing with the correct marine
organisms inhabiting the represented environment.
environment.
How do you describe,
describe, in two words,
words, the represented
environment?
environment?
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
How do the organisms inhabiting this environment move?
move?
1…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
2…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
3…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
4…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
Can you describe their shape and body colour?
colour?
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
Mod. 1
Fact Sheet R 4
“MARINE ENVIRONMENTS”
After observing the marine organism in the tanks,
tanks, fill
the following drawing with the correct marine
organisms inhabiting the represented environment.
environment.
How do you describe,
describe, in two words,
words, the represented
environment?
environment?
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
How do the organisms inhabiting this environment move?
move?
1…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
2…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
3…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
4…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
Can you describe their shape and body colour?
colour?
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
Mod. 1
Fact sheet R 5
“MARINE ENVIRONMENTS”
After observing the marine organism in the tanks,
tanks, fill
the following drawing with the correct marine
organisms inhabiting the represented environment.
environment.
How do you describe,
describe, in two words,
words, the represented
environment?
environment?
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
How do the organisms inhabiting this environment move?
move?
1…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
2…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
3…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
4…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
Can you describe their shape and body colour?
colour?
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
Mod. 1
Fact Sheet E 6
“WHERE DO THEY LIVE?”
For each animal,
animal, circle the body parts concerned in
the movement.
movement. Then,
Then, try to say how it moves
and where it lives.
lives.
Environment…………
Environment…………
Environment…………
Environment…………
Environment…………
Environment…………
…………………………
…………………………
…………………………
Movement……
Movement……..
…….. …….
…….
Movement……
Movement……..
…….. …….
…….
Movement……
Movement……..
…….. …….
…….
…………………………
…………………………
…………………………
Environment…………
Environment…………
Environment…………
Environment…………
Environment…………
Environment…………
…………………………
…………………………
…………………………
Movement……
Movement……..
…….
…….. …….
Movement……
Movement……..
…….
…….. …….
Movement……
Movement……..
…….
…….. …….
…………………………
…………………………
…………………………
Environment…………
Environment…………
Environment…………
Environment…………
Environment…………
Environment…………
…………………………
…………………………
…………………………
Movement……
Movement……..
…….. …….
…….
Movement……
Movement……..
…….. …….
…….
Movement……
Movement……..
…….. …….
…….
…………………………
…………………………
…………………………
Mod. 1
Fact sheet E 7
“THE 4 CARDS GAME”
Observe the organisms and place them in the
right card.
Animals transported by
ocean streams
(PLANKTON)
Animals from offoff-shore
waters able to swim against
the stream
…………………………………
(NEKTON)
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
Animals living on the sea
floor able to make little
movements
(MOBILE BENTHOS)
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
Animals living fixed on the
sea floor
(SESSILE BENTHOS)
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
…………………………………
Mod. 1
Fact Sheet R 8
“WATCH OUT FOR THE
MOUTH!”
Observe the following animals in tanks and draw their
respective mouths.
mouths. Then,
Then, for each one,
one, indicate what
it eats.
eats. You can choose the last two animals!
animals!
SHRIMP
SHARK
What does it eat?
eat?……………… What does it eat?
eat?………………
…………………………………...
…………………………………... …………………………………...
…………………………………...
CRAB
AMBERJACK
What does it eat?
eat?……………… What does it eat?
eat?………………
…………………………………...
…………………………………... …………………………………...
…………………………………...
…………………………
…………………………
What does it eat?
eat?……………… What does it eat?
eat?………………
…………………………………...
…………………………………... …………………………………...
…………………………………...
Mod. 1
Fact Sheet E 9
“ONE CHAIN THRIEVES
ANOTHER ONE”
Observe the represented organisms in their
respective marine environments,
environments, then fill the following
trophic chains with the missing rings listed hereunder.
hereunder.
4
2
1
3
Phyto plankton
Zooplankton
…………………
Grouper
…………………
Sea snail
…………………
Grouper
Plankton
Mussel
Crab
…………………
Mod. 1
Fact Sheet E 10
“CHAINS OR NETWORKS?”
Answer the following questions based upon the
previous fact sheet.
sheet.
What would happen if the phytoplankton disappeared?
disappeared?
………………………………………………………………………………………………………
………………………………………………………………………………………………………
What would happen if the crab population grew up
without control?
control?
………………………………………………………………………………………………………
………………………………………………………………………………………………………
What would happen if predators disappeared?
disappeared?
………………………………………………………………………………………………………
………………………………………………………………………………………………………
Now choose an animal and place it in the central ring. Then
connect it,
it, with arrows,
arrows, to all its predators and preys placed in the
other rings,
rings, specifying “who eats who”
who”. At the end do you obtain a
chain or a network?
Compare your scheme with those of your classmates.
classmates.
Mod. 1
Fact Sheet R 11
“THE IDENTIKIT”
Find out in the tanks and draw an animal…
animal…
…How can you distinguish the male and the female.
female.
MALE
…Which one lays eggs?
eggs?
FEMALE
…Which one give birth?
Mod. 1
Fact Sheet E 12
“LIFE IS A RING-A-RING-AROSES”
Answer the following questions.
questions.
Why do a lot of marine organisms lay thousands or
millions of eggs in the sea transported by the currents?
currents?
……………………………………………………………………………………………………
……………………………………………………………………………………………………
……………………………………………………………………………………………………
……………………………………………………………………………………………………
Why do others give birth to few or only one single baby?
……………………………………………………………………………………………………
……………………………………………………………………………………………………
……………………………………………………………………………………………………
……………………………………………………………………………………………………
Put in the right sequence the following phases of the life.
Birth
……
……
Growth
Mating/
Mating/reproduction
Adulthood
……
……
Mod. 1
Fact Sheet T 13
“DRAW AN ECOSYSTEM”
Choose an ecosystem (pelagic,
pelagic, rocky,
rocky, sandy
coasts or posidonia meadows)
meadows) and draw it
together with the organisms inhabiting it.
it. For
each element indicate its name.
name.
Now try to list some of the drawn elements and specify,
specify, for each one,
one,
its respective role within the ecosystem.
ecosystem.
ELEMENT
ROLE
………………………………………
………………………………………
………………………………………
………………………………………
………………………………………
………………………………………
………………………………………
………………………………………
………………………………………
………………………………………
Mod. 1
Fact Sheet T 14
“BUILD UP YOUR NETWORK!”
Try to build up a trophic network which characterizes
one of the studied ecosystems.
ecosystems.
Ecosystem ..……………………………………………………………
..……………………………………………………………..
……………………………………………………………..
Check your network with one of your classmates who chose the
same ecosystem.
ecosystem.
Mod. 1
Fact Sheet T 15
“INVENT A STORY”
Now that you have discovered so many things about life
in the sea,
sea, choose an animal and write a story about its
life. You can add some drawings,
drawings, too.
too.
Title ……………………………………………………………………………………...
……………………………………………………………………………………...
.………………………………………
……………………………………….
……………………………………….
……………………………………….
……………………………………….
……………………………………….
……………………………………….
……………………………………….
……………………………………….
……………………………….............
……………………………….............
……………………………………….
……………………………………….
.……………………………………………………………………………………..
……………………………………………………………………………………..
………………………………………………………………………………………
………………………………………………………………………………………
.………………………………………
……………………………………….
……………………………………….
……………………………………….
……………………………………….
……………………………………….
……………………………………….
……………………………………….
……………………………………….
……………………………….............
……………………………….............
……………………………………….
……………………………………….
Read your story in class.
class.
Mod. 1