Download ecological succession

Biodiversity and species
Week six
The role of each species in an ecosystem
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Ecological niche: each species has a distinct role to
play in the ecosystems where it is found. It is a
species way of life in a community and includes
everything that affects its survival and production
(such as water, kind of feed, space, sunlight,
temperature etc it needs). It is its pattern of living
and is different from its habitat.
Niche is used for classifying the species into:
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Generalist species: species with a broad niche and ability to live in
many different places, eat various foods, tolerate range of environmental
conditions. (flies, cockroaches, mice, rats, raccoons, and human)
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Specialist species: species that occupy narrow niches and able to
live in only one type of habitat, eat a few types of food, and tolerate a
narrow range of climatic and environmental conditions
Classification of species by using Niche
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Niche classified in terms of species roles within ecosystems to five role
and certain species may play one or more of these roles:
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Native Species: are those that normally live and thrive in a particular
ecosystem.
Nonnative Species: are those that migrate or deliberately or accidentally
introduce into an ecosystem. They also called invasive, alien, or exotic
species.
Indicator Species: provide early warnings of damage to community or an
ecosystem such as trout for water quality, birds for environmental changes,
butterflies for plant and habitat loss, amphibians for environmental
condition and pollution and increase in UV and climate change and global
warming,
Keystone Species: are the species that have a large effect on the types and
abundances of other species in an ecosystem. (pollination or top predator)
Foundation Species: play a major role in shaping communities by creating
and enhancing their habitats in ways that benefit others. (elephants for
forest openings, Beavers making wetlands, birds draping seeds)
How do species interact
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Five basic types of interaction between species for
sharing limited resources such as food, light, shelter, and
space:
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Interspecific competition: ‫ رقابت دورن گونه ای‬occurs when members of
two or more species interact to gain access to the same limited
resources
Predation: ‫ شکاری‬occurs when a member of one species (predator)
feeds directly on all or part of member of another species(prey)
Parasitism: ‫ طفیلی‬occurs when one organism (parasite) feeds on the
body of, or the energy used by, another organism (host), usually living
on or in the host
Mutualism: ‫ همزیستی‬is an interaction that benefits both species by
providing each one limited resources
Commensalism: ‫ همسفرگی‬is an interaction that benefits one species but
has little, if any, effect on the other
Conclusion: these interaction have significant effects on the
resources use and population sizes of the species in an ecosystem.
Natural Selection and Reduction of
Competition between Species
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Some species develop adaptation that allow them to
reduce or avoid competition with other species for
resources
Resource partitioning is a way to realize it and occur
when species competing for similar scarce resources
evolve specialized traits that allow them to use shared
resources at different time, in different ways, or different
places
populations
S. A
S. B
niche overlap
Resource Use
A
B
Limits of the growth of populations
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No population can continue to grow indefinitely because
of:
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Population characteristics:
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Limitation on resources and;
Competition among species for those resources
Distribution
Numbers
Age structure
Density
Population Dynamics: is a study of how population
characteristics evolve in respond to environmental changes
(such as temperature, presence of diseases and harmful chemicals, resource availability, in or
out competing species)
Species population distribution or dispersion ‫پراکندگی‬
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Dispersion of a species in a habitat includes:
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clumps or Patches ‫گله ای یا لکه ای‬
Uniform dispersion: is for mentioning a fairly constant distance between
individuals to have better access to scarce resources
Random dispersion :which are fairly rare ‫پراکندگی تصادفی‬
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The living world is mostly clumpy or patchy
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Clumping happens because of:
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Availability and concentration of resources that a species needs, in a
certain places and environmental conditions
Moving in groups create better chance of encountering resources
living in groups protects some individuals from predators
Hunting in packs gives some predators a better chance of finding and
catching prey
Grouping makes mating and caring for young easier
Population and Age Structure
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Population’s Age Structure: is the proportions of
individuals at various ages and usually divided to:
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Pre-reproductive age
Reproductive stage
Past- reproduce- live stage
Population change = (Births + Immigration) - (Deaths + Emigration)
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Biotic potential: ‫ ظرفیت رشد جمعیت در شرایط ائده آل‬:‫توان حیات‬
is the capacity for population growth under ideal
conditions
Generally large species have low B.P. Such as elephants
and small individuals have high B.P. such as bacteria.
Intrinsic rate of increase
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Intrinsic rate of increase (r): ‫ نرخ رشد ذاتی یا طبیعی‬is the
rate at which the Biotic potential of a species would grow
if it had unlimited resources.
Population with high (r) has following characteristics:
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Reproduce early in life;
Have short generation time;
Can reproduce many times; and
Have many offspring each time they reproduce.
There are always limits to Population Growth in nature.
Limiting factors for growth:
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Light and Space, Water and Nutrients,
Many competitors, predators, and infection disease.
Logistic Growth Curve ‫منحنی رشد منطقی‬
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Environmental resistance: is the combination of all factors that act to limit
the growth of population.
‫ ترکیبی از تمامی عوامل محدود کننده رشد است‬:‫ مقاومت محیطی‬
Carrying Capacity: ‫ توان تحمل‬the maximum population of a given species that
a particular habitat can sustain indefinitely without being degraded.
‫ حداکثرجمعیت یک گونه در داخل یک زیستگاه در شرائط پایداری بلند مدت و بدون‬:‫ توان تحمل‬
.‫تخریب آن است‬
 J – Curve: rapid exponential population growth.
 S – Curve: a plot of number of individuals against time yields a sigmoid or S
– Shaped curve.
 Logistic Growth Curve: It involves rapid exponential population growth
followed by a steady decrease in population growth until the population
size levels off.
‫این منحنی شامل رشد سریع نمایی جمعیت گونه وسپس کاهش تدریجی رشد جمعیت تا دستیابی‬
.‫به سطح تعادل جمعیتی است‬
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Interaction of Biotic Potential and Environmental Resistance
Species Reproductive Patterns
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r- selected species: ‫ قورباغه ها‬،‫ باکتریها‬،‫ گیاهان تکساله‬،‫ جلبکها‬،‫حشرات‬
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k- selected species:‫ گیاهان چند ساله‬،‫ انسانها‬،‫ والها‬،‫پستانداران بزرگ مثل فیلها‬
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Many, small, little or no parents protection or care, mass
mortality of offspring with sort time life
They are opportunists, reproduce rapidly by favourable
environmental conditions
Irregular and unsustain boom and bust cycles in population size
Reproduce late in life, small number of offspring, born fairly
large, mature slowly, cared by 1 or both parents, living in
groups
Their population follow a logistic growth curve, population size
is near to carrying capacity (k)
Normal species: most of organisms reproductive pattern is in
between
‫‪Affects on population size‬‬
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‫‪Genetic diversity:‬‬
‫کاهش تنوع ژنتیکی در داخل یک گله منجر به کاهش جمعیت آن گونه‬
‫میگردد از طریق‪:‬‬
‫اثر بنیان گذار ‪Founder effect‬‬
‫اثر جمعیت نجات یافته از حوادث ‪Demographic bottleneck‬‬
‫اثرغلبه ژنیتیکی (یک گروه با توان تولید نسل بیشتر در داخل یک گله)‪Genetic drift‬‬
‫اثر فامیلی (تولید نسل در داخل یک فامیل)‪Inbreeding‬‬
‫اثر منزوی شدن یک گروه ‪Island biogeography‬‬
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‫‪Population density:‬‬
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Types of population fluctuation (change)
in Nature
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‫در طبیهت چهار الگوی اصلی تحول جمعیتی یافت میگردد‬
Stable: population size fluctuate slightly above or below
carrying capacity
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Many of r-selected species
Depends of seasonal weather and nutrient availability
Cyclic fluctuation: ‫جهش جمعیتی در یک دوره زمانی مشخص‬
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Species living in undisturbed areas with stable annual average
temperature
Irruptive: population exploded to high pick and then crash
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Lemmings in 3-4 years‫موش صحرایی قطبی‬, lynx‫ سیاهگوش‬and
snowshoe hare ‫ خرگوش قطبی‬in every 10 years
irregular change with no recurring pattern
Theory of ecological succession and
Natural ecological restoration
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The structure and species composition of communities and
ecosystems change in response to changing environmental
conditions through a process called ecological succession.
ecological succession: the gradual change in species composition
in an area, while some species colonize the area and their population
increase and population of other species decrease or disappear.
 Stat by arriving colonizing or pioneer species and environmental changes
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Primary succession: the gradual establishment of biotic
communities in lifeless areas with no soil or bottom sediment
Secondary succession: a series of communities and
ecosystems with different species develop in an area contain
soil (terrestrial) or bottom sediment (aquatic)
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Succession doesn’t follow a predictable path (no balance of nature)
Living systems are sustained through constant change
Nature’s four scientific principals of
sustainability
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Reliance on solar Energy: the sun warms the planet and
supports photosynthesis used by plants to provide food for
themselves and for us and most other animals.
Short for Biological diversity: the astounding variety of
different organisms, the genes they contain, the ecosystem in
which they exist, and natural services they provide have
yielded countless ways for life to adapt to changing
environmental conditions throughout the earth’s history.
Population Control: competition for limited resources among
different species places a limit on how much their populations
can grow.
Nutrient Cycling: natural processes recycle chemicals that
flora and fauna need to stay alive and reproduce.
Usage of Four Scientific Principles of
sustainability
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To design of our economic and social systems;
To design our individual lifestyles;
To help slow human population growth;
To sharply reduce poverty;
To curb unsustainable forms of resource use and save
natural capital;
Create a better world for ourselves, our children, and
future generations