Environmental Science
A Study of Interrelations
环境科学
－交叉关系学科
Hebei University of Science and Technology
河北科技大学
School of Environmental Science and Engineering
环境科学与工程学院
Li Shuang-jiang
李双江
Chapter 5 Interactions: Environments and
Organisms
Outline
Ecological Concepts
The Role of Natural Selection and
Evolution
Kinds of Organism Interactions
Community and Ecosystem Interactions
一、 Ecological Concepts
¾ The definition: the science of ecology is the
study of the ways organisms interact with
each other and with their nonliving
surroundings.
¾ Everything that affects an organism during
its lifetime is collectively known as its
environment. It is useful to subdivide the
concept of environment into abiotic
(nonliving) and biotic (living) factors.
Levels of
Organization in
Ecology
The study of
ecology can
take place at
several
different levels
as shown in
the figure.
一、 Ecological Concepts
¾ Although
organisms
interact
with
their
surroundings in many ways, certain factors may
be critical to a particular species’ success. A
shortage or absence of this factor restricts the
success of the species, thus, it is known as a
limiting factor.
The availability of raw materials
Limiting factors
The availability of energy
The accumulation of waste products
Interactions among organisms
Limiting Factors In a aquatic habitats, the amount of oxygen
dissolved in the water is often a limiting factor for many species of
fish. Cool, highly oxygenated water, which is typical of the rapidly
flowing upper sections of a river system, supports trout, but warmer,
less oxygenated water is unsuited for trout.
一、 Ecological Concepts
¾ The habitat of an organism is the space
that the organism inhabits, the place where
it lives (its address).
¾ The niche of an organism is the functional
role it has in its surroundings (its
profession).
Moss Habitat
The habitat of
mosses is
typically cool,
moist, and
shady. Mosses
must also have a
thin layer of
water present.
The Niche of a Dandelion A dandelion serves as food to various
herbivores, supplies nectar to bees, and can regrow quickly from its
root if its leaves are removed
二、 The Role of Natural
Selection and Evolution
Genes, Populations, and Species
¾ Genes are distinct pieces of NDA that determine
the characteristics an individual displays.
¾ A population is considered to be all the organisms
of the same kind found within a specific
geographic region.
¾ A species is a population of all the organisms
potentially capable of reproducing naturally among
themselves and have offspring that also
reproduce.
二、 The Role of Natural
Selection and Evolution
Natural Selection
¾ Natural selection is the process that
determines which individuals within a
species will reproduce and pass their genes
to the next generation.
¾ The changes that we see in the genes and
the characteristics displayed be successive
generations of a population of a organisms
over time is known as evolution.
二、 The Role of Natural
Selection and Evolution
Evolutionary Patterns
¾ The production of new species from previously
existing species is known as speciation (物种形成)
and is thought to occur as a result of a species
dividing into two isolated subpopulation.
¾ Extinction is the loss of an entire species and is a
common feature of the evolution of organisms.
¾ Coevolution is the concept that two or more
species of organisms can reciprocally (相互的)
influence the evolutionary direction of the other.
Evolutionary Change: Populations of weed plants that have been
subjected repeatedly to herbicides often develop resistant populations.
三、 Kinds of Organism
Interactions
¾ Predation occurs when one organism, known as a
predator, kills and eats another, known as prey.
Predator-Prey Relationship: Lions are predators of zebra. The
quicker lions are more likely to get food, and the slower, sickly or
weaker zebra are more likely to become prey.
三、 Kinds of Organism
Interactions
¾ Competition: two organisms strive to obtain
the same limited resource.
¾ Intraspecific competition: members of the
same species compete for resources.
¾ Interspecific
competition:
competition
between organisms of different species.
三、 Kinds of Organism
Interactions
Competition: The white-backed vultures are engaged in
intraspecific competition for the remains of this carcass.
三、 Kinds of Organism
Interactions
Parasitism （寄生）
Symbiotic (共生的) Relationships
Commensalism (共栖)
Multualism (互利)
¾ Parasitism: one organism (parasite) lives in or on
another organism (host), from which it derives
nourishment.
¾ Commensalism: one organism benefits while the
other is not affected.
¾ Mutualism: benefit to both species involved.
三、 Kinds of Organism
Interactions
The examples
of parasitism
三、 Kinds of Organism
Interactions
The examples of parasitism
绦虫
水蛭
七鳃鳗
Parasitism
Ectoparasites(体外寄生虫):
Fleas are small insects that live
in the feathers of birds or the
fur of mammals, where they
bite their hosts to obtain blood.
Endoparasites (体内寄生虫):
Tapeworms live inside the
intestines of their hosts, where
they absorb food from their hosts’
intestines.
三、 Kinds of Organism
Interactions
The examples of mutualism
¾Most flowering plants and
their pollinators are mutualists.
¾The pollinators receive food
from the plant in the form of
nectar or pollen, and they
provide the plants with an
accurate pollen-delivery system.
三、 Kinds of Organism
Interactions
The examples of mutualism
¾A similar mutualism occurs between nitrogen – fixing
bacteria (Rhizobium and Bradyrhizobium) and certain
legumes.
¾These bacteria enter through the plants root hairs and
invade the root cortex.
¾The root cells and the bacteria within them divide to
form a swollen mass of tissue called a root nodule.
三、 Kinds of Organism
Interactions
Root nodule
三、 Kinds of Organism
Interactions
Remoras
Shark
Commensalism:
Remoras hitchhike a ride on sharks and feed on
the scraps of food lost by the sharks.
三、 Kinds of Organism
Interactions
¾ Human interaction– a different look: we have
complicated interactions with other organism.
‡ Predator
‡ Herbivore (草食动物)
‡ Scavenger (腐食动物)
‡ Commensalism
‡ Parasitism
‡ Mutualism
‡ Competition
三、 Community and Ecosystem
Interactions
¾ A community is an assemblage of all the
interacting populations of different species of
organisms in an area.
¾ An ecosystem is a defined space in which
interactions take place between a community, with
all its complex interrelationships, and the physical
environment.
¾ The concepts of community and ecosystem are
closely related, an ecosystem is a broader
concept because it involves physical as well as
biological processes.
三、 Community and Ecosystem
Interactions
Major Roles of Organisms in Ecosystems
¾ Producer
Primary consumer: herbivore
¾ Consumer Secondary consumer: carnivore
Omnivore (杂食动物)
¾ Decomposer
三、 Community and Ecosystem
Interactions
Major Roles of Organisms in Ecosystems
Table 5.1 Role in a ecosystem
category
Major Role or Action
Example
Producer
Convert simple inorganic molecules into
organic molecules by the process of
photosynthesis
Trees, flowers, grasses,
ferns, mosses, algae
Consumer
Use organic matter as a source of food
Animals, fungi, bacteria
Herbivore
Eats plants directly
Grasshopper, elk, huma
vegetarian
Carnivore
Kill and eats animals
Wolf, pike, dragonfly
Omnivore
eats both plants and animals
Rats, raccoons, most humans
Scavenger
Eats meat but often gets it from animals
that died by accident or illness, or were
killde by other animals
Coyote, vulture, blowflies
Parasite
Live in or on another living organism and Tapeworm, many bacteria,
gets food from it
some insects
Decomposer
Returns organic material to inorganic
material;completes recycling of atoms
Fungi, bacteria, sone insects
and worms
三、 Community and Ecosystem
Interactions
¾ A keystone species is one that has critical role to
play in the maintenance of specific ecosystems.
¾ Each step in the flow of energy through an
ecosystem is known as a trophic level.
¾ Approximately 90 percent of the useful energy is
lost with each transfer to the next highest trophic
level.
¾ The biomass is the weight of living material in a
trophic level.
三、 Community and Ecosystem
Interactions
Energy flow through ecosystem
¾Often, the trophic structure of an ecosystem
is represented as an ecological pyramid in
which producers form a base for successive
tiers of consumers above them.
¾Some pyramids are based on biomass (the
weight of all the members at which trophic
level), others on energy flow.
Biomass pyramid
Energy Flow Through an Ecosystem: Energy passes through several
trophic levels each containing a certain amount of energy. Each time energy
flows to another trophic level, about 90% of the useful energy is lost. Therefore,
higher trophic levels often contain less energy and fewer organisms.
三、 Community and Ecosystem
Interactions
¾ The passage of energy from one trophic
level to the next as a result of one organism
consuming another is known as a food
chain.
¾ When several food chains overlap and
intersect, they make up a food web.
Food Chain
As one organism feeds on
another organism, energy flows
through the series.
三、 Community and Ecosystem
Interactions
三、 Community and Ecosystem
Interactions
A marine food web
三、 Community and Ecosystem
Interactions
Detritus food web
三、 Community and Ecosystem
Interactions
Nutrient cycles in ecosystems– biogeochemical cycles
The activities involved in the cycling of
atoms include biological, geological, and
chemical processes. Therefore, these
nutrient
cycles
are
often
called
boigeochemical cycles.
三、 Community and Ecosystem
Interactions
Carbon cycle
¾It is one of the most important of all atmospheric
cycles.
¾ Most of the earth’s carbon is dissolved in the
ocean.
¾Soil, the atmosphere, and plant biomass represent
other large ‘holding stations’ for carbon.
¾Most carbon in the atmosphere is in the form of
carbon dioxide (CO2).
Carbon Cycle
三、 Community and Ecosystem
Interactions
Nitrogen cycle-- N-fixation by microorganisms
¾The conversion of gaseous nitrogen to forms that are
useful to plants – ammonia (NH3) and ammonium (NH4+)
is carried out primarily by microorganisms. (P98 fig. 5.17)
三、 Community and Ecosystem
Interactions
Nitrogen cycle
三、 Community and Ecosystem
Interactions
Phosphorus cycle
¾Phosphorus is typically present in rock
formations on land, in the form of
phosphates.
¾Through the natural processes of
weathering and erosion, phosphates enter
rivers and streams, which eventually
transport them to the ocean.
¾P102 fig.5.31
Phosphorus Cycle
三、 Community and Ecosystem
Interactions
Human impact on nutrient cycles
¾To C-cycle: burning fossil fuel and converting
forests to agricultural land
¾N-cycle: fertilizer
¾To P-cycle:
9First, we mine large quantities of phosphate rock
for use in fertilizers and detergents.
9Second, we add excess phosphate to aquatic
ecosystems through our use of fertilizers,
phosphate-containing detergents, and discharges
from municipal sewers.
Microcystis bloom
Dianchi Lake, Yunnan Province, China
Cyanobacteria and
Microcystis bloom
2007-5-10, Taihu Lake, Wuxi City, Jiangsu
province, China
Pollution of Taihu Lake, the
drinking water is shortage.
Thanks for Attention！