Download Ecology is the study of the living world and the interactions among

1/12/17
Ecology is the study of the living world and the interactions among organisms and where they
live.
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The environment in which a living thing exists is made up of abiotic and biotic parts. Abiotic are non-living
parts which include air, water, rocks and minerals, and sunlight. Biotic are the living parts such as monera
(bacteria), plants, protists (algae), fungi and animals, the five major Kingdoms. Ecologist look at the
interactions between plants and animals, the biotic and their environments, the abiotic. An animal’s
environment is everything in its surroundings.
An ecosystem is a community of biotic (living organisms: plants, animals and microbes) and abiotic
(nonliving: air, water, minerals, soil) things that work together, interacting as a system; it is the community of
species and habitats linked together by the flow of food and energy. Ecosystems form the biosphere of the
Earth, where living things are found. Ecosystems are made up of species adapted to the conditions of that
community.
To clarify the difference between an ecosystem and an environment: The environment refers to the
surroundings where an animal lives. The term “environment” does not include the relationships that exist
between the living and the physical attributes of the surroundings. The ecosystem includes these interactions
between the environment and the organisms that dwell within it.
A habitat is the specific environment in which any given organism or any given population lives. It is the
“address” of the organism. A habitat contains everything that an animal needs to survive, including air, food,
water, shelter, sun, space and other animals.
An animal’s niche refers to the “role” or “job” a species plays in its environment; it describes the way of life
of that species. The ecological niche describes how an organism or population responds to the distribution of
resources and competitors. For example, the niche of a two-toed sloth would be a herbivorous, nocturnal
species of the understory and canopy of certain rainforest tree species.
Each species is thought to have a separate, unique niche. No two species can occupy exactly the same niche;
this is known as the principle of competitive exclusion. Species may share the same habitat, but their roles
(or jobs) are different. If two species are competing for the same niche, the one that is best adapted to the
range of conditions present will survive by having the higher birth rate and/or lower death rate.
In natural situations, species that might compete have evolved ways to reduce competition and divide
resources. They may use the habitat at different times of day (temporal separation) or use different parts of
the habitat (spatial separation). Competition for resources affects the number of individuals in a particular
species and the total number of species that can coexist in a given habitat.
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Remember a niche is the ecological role and space that an organism fills in an ecosystem. In
describing a niche, you want to ask where it lives, when it is active and what it eats.
The correct answers are:
Giraffe: b) Terrestrial, diurnal, herbivorous browser of the tallest trees especially acacia
Koala: a) Arboreal, nocturnal, herbivorous
Giant Anteater: e) Terrestrial, mostly nocturnal, insectivorous
African Lion: d) Terrestrial, nocturnal/crepuscular, carnivorous
Indian Hornbill: c) Arboreal, diurnal and omnivorous
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Almost all of life on the surface of the earth is fueled by the enormous amounts of energy
intercepted from the sun by the light-absorbing pigment chlorophyll in the plant’s leaves. This
energy fuels a chemical reaction between with carbon dioxide and water to produce glucose,
the main fuel that powers life; in this way, plants are producers and make their own nutrients.
Carbon dioxide is brought in from the atmosphere through stomatas (holes) in the leaves and
water is brought to the leaves through vessels that start in the plant’s roots in the soil. Oxygen
is a by-product of this reaction and is released into the air. This is the process of
photosynthesis. The oxygen released during photosynthesis can be used during respiration by
both plants and animals. Plants must respire just as animals do; they take in oxygen and give
off carbon dioxide. Their photosynthetic activity is however greater than their respiratory
activity resulting in an increase in atmospheric oxygen levels.
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Scientists frequently describe the interactions within an ecosystem in terms of exchanges of energy
and nutrients. Plants derive energy from the sun and nutrients from the earth; they in turn supply both
to the animals.
A simple food chain is based on who eats who; plants are the producer, and make their own energy
by photosynthesis. All other living things are consumers; they get energy from the food they eat;
they survive by eating a producer, or another consumer that ate a producer, gaining the chemical
energy from the original process of the producer. A primary consumer or herbivore, eats plants
whereas a secondary consumer eats a primary consumer and is a carnivore. An omnivore may eat
both meat and vegetation. Folivores eat only stems and leaves. Frugivores eat only fruit.
Insectivores eat only insects.
Decomposers break down dead plant and animal matter at any level and help recycle nutrients back
into the soil so that they can be used again. In this way nutrients are cycled through the food chain.
Nutrients are inorganic compounds such as phosphorous which is in your teeth, bones, and cellular
membranes, nitrogen which is part of your amino acids, the building blocks of protein and the iron in
your blood.
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Food chains are linear and interconnect to form food webs. A food web shows the more complex
relationships present in ecosystems, with circular patterns between producers and consumers. The
example on this slide shows an example of a food web in the San Francisco area.
All living things are closely related to their environment; any change in one part of an
environment, like an increase or decrease of a species of animal or plant, causes a ripple effect of
change in through other parts of the environment. All species depend on each other to survive, so
if one becomes extinct another species that relies on it could go extinct as well. Individual traits
can allow some species to adapt to environmental changes, but many species cannot adapt if their
habitat and food chains are greatly altered.
Deficiency in any one part of a habitat’s ecosystem changes the entire system. If the deficiency is
too great, the entire ecosystem can collapse and many species may decline or disappear. Diversity
would decrease. A keystone species is one where many other species depend upon its abundance
as prey for their survival. Losing individual species is like playing Jenga, where you pull building
blocks from a stack, one by one, until the whole stack collapses.
Examples of keystone species include pacific tree frogs and garter snakes. Also, bees &
hummingbirds are major pollinators and plants are shelter and food for other animals so loosing
them would be a major problem for our ecosystems.
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The trophic level of an organism is the position it occupies in a food chain; it is the number of steps an
organism is from the start of the chain. The plants (producers are on the first trophic level and the eagle is
on the fourth trophic level.
Energy is transferred from the producer, to herbivore, to predator and finally decomposer in an ecosystem.
(Note: a decomposer act as a consumer at any level). This transfer of energy through the trophic levels is
called energy flow. On the first trophic level, plants are able to collect about 1% of the sun’s energy. At
each successive trophic level only 10% of available energy is transferred to the next level. The rest is used
up in metabolic processes or in movement and is lost as heat and cannot be created or recycled as nutrients.
Biomass refers to the collective mass of the biological material derived from living, or recently living
organisms in an ecosystem at any given time. The amount of biomass at each trophic level as you go up the
pyramid becomes less; the available energy is less. This is why each level supports fewer individuals than
the one before. It is also why food chains rarely contain more than five steps.
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This statement is true. Nutrients are cycled through a food web and returned to the soil be the
decomposers. Energy on the other hand is lost at each trophic level to the environment as heat.
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Biologists divide the planet up into different regions that share characteristic vegetation, climate, and
wildlife. These biomes are a specific kind of ecosystem and are defined by climate and dominate plants.
The climate is mainly determined by the temperature and rainfall. A biome has a distinctive plant
formation and because animal groups depend on plants, each biome supports a characteristic fauna, which
are adapted to that particular environment. Each biome consists of many ecosystems whose communities
have adapted to the small differences in climate and the environment inside the biome.
There are five principal biomes that you should be aware of:
The aquatic biome includes freshwater habitats (ponds, lakes, streams, wetlands) as well as marine
habitats (ocean, coastal waters, estuaries, coral reefs).
The desert biome includes areas where rainfall is less than 10 inches/year. Desert habitat types include hot
and dry, semiarid, coastal, and cold.
The forest biome includes areas that are dominated by trees and other woody vegetation.
The grassland biome includes habitats dominated by grasses (not trees and shrubs). Grasslands include
tropical savannas and temperate grasslands (prairies).
The tundra biome includes cold habitats with low biotic diversity and simple vegetation structure. The
tundra biome includes arctic tundra and alpine tundra habitats. The tundra and desert biomes occupy the
most extreme environments, with little or no moisture and extremes of temperature. These two biomes
have the fewest numbers of species due to the stringent environmental conditions.
Factors that determine whether an organism can live in a specific biome include climate (temperature,
rainfall, light, and altitude), available food sources, available plant life (provides food and shelter), other
species it interacts with and predators (presence or absence of). We will be discussing adaptations animals
have in order to live in each of these biomes when we discuss the individual animals.
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The freshwater and marine biomes are probably the most important of all the biomes. Their medium, water, is a
major natural resource. Water is the basis of life, it supports life, and countless species live in it for all or part of
their lives. Freshwater biomes supply us with our drinking water and water for crop irrigation.
The world's oceans regulate Earth’s climate and have an even greater effect on global climate than forests do.
Water has a high capacity for heat, and because the Earth is mostly covered with water, the temperature of the
atmosphere is kept fairly constant and able to support life. Oceans circulate heat and water throughout the
planet, establishing the underlying conditions that lead to storms and rainfall patterns that can cause droughts
and floods.
In addition to this climate-buffering capacity, the oceans contain several billion photosynthetic plankton which
account for most of the photosynthesis occurring on Earth. Without these, there might not be enough oxygen to
support such a large world population and complex animal life.
Three quarters of the earth’s surface is made of the five major oceans. The ocean biome can be divided up into
vertical zones based on the depth of the water. Oceanic organisms are placed in either pelagic (open water) or
benthic (ocean floor). We will not be going into detail in this class of the Ocean biome.
The types of life that live in the ocean biome are extremely diverse; conditions in water are generally less harsh
than those on land. Since the temperatures in any ocean biome can be very cold, the animals have been able to
adapt. For example whales have thick layers of fat known as blubber. This helps them to keep their body
temperature where it should be. Oxygen is essential for all living things including marine animals; animals tend
to be closer to the surface, where the oxygen is more plentiful than the deepest oceans. Fish use gills to breath
and mammals must come to the surface to breath air. Aquatic organisms are buoyed by water support, and do
not usually have to deal with desiccation. They are usually streamline for swimming. They also must be able
to regulate the salt in their systems.
The zoo has California sea lions, Magellanic penguins and the white and brown pelicans who occupy a marine
environment.
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The freshwater biome is subdivided into two zones: running waters and standing waters.
Larger bodies of freshwater are less prone to stratification (where oxygen decreases with
depth). The upper layers have abundant oxygen, the lowermost layers are oxygen-poor.
The freshwater biome is a location where there is plenty of nutrition and minerals. That is why
so many types of plants and animals are able to thrive in such a location.
Freshwater is an important resource for animals that live within them as well as on land; more
than half of the drinking water for humans and animals comes from this resource. Land
animals depend on lakes for hydration and food; amphibians are highly dependent on water for
reproduction; diving birds, storks and waterfowl depend on freshwater resources, reptiles such
as turtles, alligators, and water snakes live most of their lives in or next to freshwater;
mammals such as bears, otters, and beavers are found only near these habitats. Many fish and
insects and other invertebrates are found only in freshwater.
Some of the same adaptations that are seen in the marine environment are seen in the
freshwater environments. Animals are usually streamline for swimming and are insulated for
the temperatures.
Some of the zoo animals that we have that occupy a freshwater habitat are the green anaconda,
the North American river otter and capybara.
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Deserts are hot and dry. They cover about one fifth of the Earth's land surface. Deserts receive less
than ten inches of rain per year. The Sahara and a few other deserts have almost no vegetation. Most
deserts, however, are home to a variety of plants, all adapted to heat and lack of abundant water
(succulents and cacti).
Thus water conservation is very important for all plants in the desert. Plant must be able to respond
quickly to the rain so that they can produce their seeds before things dry out again. Plant characteristics
include fleshy, columnar stems of cactus which provide water storage, protective spines, reduced leaves
and thick waxy shiny surfaces to hold water in. The saguaro cactus extracts water from its environment
every chance it gets. Its roots just below the surface and stretch out widely, so it can soak up as much
rain and dew before it evaporates. The saguaro also has a spongy inside layer that helps distribute water
in the plant. Its outside skin is pleated, so when more water is absorbed its outside can expand to make
room.
Other plants have developed very long roots that go deep into the ground to reach underground water
like the mesquites. Eucalyptus leaves orient vertically and only show surface of leaves during morning
and afternoon but not at noon. Some plant have small leaves or others shed leaves in summer to avoid
water loss. The Palo Verde bark is green because it contains chlorophyll and can carry on
photosynthesis after the leaves are shed. Other plants may go into a dormancy period during the summer
months.
There is very limited types of plant and animal life that are able to live in the desert biome; desert
animals have evolved both behavioral and physiological ways to the temperature, water stresses and
little food that the desert environment creates. The majority of the animals living in the desert biome are
nocturnal. This means they sleep during the heat of the day and they are active at night when the sun
goes down. Desert animals don’t need to feed very often which is why almost all of them are very
small. They also don’t need to find water independently. They get the water they need from their
sources of food. Ants are quite plentiful in the desert biome. They create underground tunnels where
they are able to stay out of the heat.
Desert dwelling animals at the zoo include the desert tortoise, and the giant desert centipede.
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Today, forests occupy approximately one-third of Earth's land area, account for over two-thirds of the
leaf area of land plants, and contain about 70% of carbon present in living things. Let us now look at
two different types of forest biomes.
Temperate forest are made up of coniferous and deciduous trees and have distinct seasons and
usually cold winters. Wind pollinated species are predominant. Precipitation of some form is year
round and there is a well-defined growing season . This climate is difficult for most animals, and
many hibernate during the harshest months, or migrate for the winter such as many bird species.
Predators have a hard time finding food and may have to travel long distances.
The conifer tree species include pines, spruces and larches that can handle cold climates; needle
shaped leaves help to withstand the wind and cold, while a hard waxy surface keeps them from
drying out. Their conical shape prevents them from breaking under the added weight of snow and
ice. Lower branches help support the branches above. Tree acts like a collapsed umbrella and the
snow slides off. By not loosing their needles they are at an advantage over the deciduous trees
because they are able to start photosynthesis earlier and also they conserve energy by not having to
produce new needles each year.
Deciduous species include broad-leaved trees that shed their leaves in winter, like oaks, birch, maple,
beech, aspen. The broad leaves help capture sunlight in the summer. As the temperatures drop, the
tree cuts off the supply of water to the leaves and seals off the area between the leaf stem and the tree
trunk. Chlorophyll is withdrawn also from the leaves causing them to change into the beautiful red,
yellow and orange. Dead leaves and twigs form a decaying layer over the soil that is home to many
animals.
Sufficient sunlight penetrates the canopy to support a well-developed understory composed of
shrubs, a layer of herbaceous plants, and then often a ground cover of mosses and ferns.
Temperate forests are dominated by relatively few species in contrast to the tropical forests which
contain thousands of species, none of which dominates. Birds are plentiful here because there are
many insects for them to feed upon. You will also find quite a few larger animals living in the
temperate deciduous forest biome. Many of them such as the deer and bear eat grass and shrubs.
Temperate forest zoo animals include found here include grizzly bear, siberian tiger, wolverine and
bald eagle.
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The tropical rain forest are the richest and most diverse biome on earth; they occur in regions near the equator.
Scientists estimate that more than half of all the world's plant and animal species live in tropical rain forests, with
many more yet to be discovered. Rainforests now cover less than 6% of Earth's land surface but produce 40% of
Earth's oxygen. Seasonality is low so plants can afford to specialize; it is a warm, wet climate year round, getting
over 80 inches of rain per year, with dense vegetation. Only the tallest trees get light, so most vegetation is
adapted to grow in almost permanent shade. Distinct layers have their own species of flora and fauna, from the
forest floor, up to shrub layers, to the understory of smaller trees, to the canopy of tall trees, then to the emergent
layer of giant trees that poke out into the sun.
With its yearlong growing season, tropical forests have a rapid cycling of nutrients. Soils in tropical rain forests
tend to have very little organic matter since most of the organic carbon is tied up in the standing biomass of the
plants. These tropical soils, termed laterites, make poor agricultural soils after the forest has been cleared.
Trees have a thin, smooth bark and don’t worry about moisture loss. Many tropical rainforest leaves have a drip
tip. It is thought that these drip tips enable rain drops to run off quickly. Plants need to shed water to avoid growth
of fungus and bacteria or leaves are too heavy for the plant to support.
Plants compete for sunlight. Lianas are climbing woody vines that drape rainforest trees. They have adapted to
life in the rainforest by having their roots in the ground and climbing high into the tree canopy to reach available
sunlight. Many lianas start life in the rainforest canopy and send roots down to the ground.
Epiphytes are plants that grow on other plants. These epiphytes have their own roots to absorb moisture and
minerals, and use the other plant more as an aid to grow taller. The warm, moist climate supports high
productivity as well as rapid decomposition of detritus.
Bromeliads are found almost exclusively in the Americas. Some grow in the ground, like pineapple, but most
species grow on the branches of trees. Their leaves form a vase or tank that holds water. Small roots anchor plants
to supporting branches, and their broad leaf bases form a water-holding tank or cup. This reservoir of water
supports a thriving ecosystem of insects, amphibians, and birds.
Dominant trees are flowering with virtually no conifers occurring naturally. With high species diversity an area
might have only one or two individual of a particular species. Pollination is predominantly done by animals; wind
pollination would not be successful. Many species of plants have brightly colored flowers that are easy to see in
dim light and scents tend to be strong that insects and birds find the flowers quickly.
You will find a diverse species of insects, reptiles, birds, and various mammals. Rainforest animals at the zoo
include two-toed sloth, howler monkeys, black and white ruffed lemur, sumatran tiger, and green-winged macaw
as well as many birds, reptiles, amphibians and mammals that are in the tropical rainforest building.
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The tropical rain forest has a complex structure, with many levels of life; a distinct feature of tropical forest is
stratification of life into 6-8 feeding strata. Here is a profile of a tropical forest, showing vertical differentiation of
animal and plant life into six feeding strata. The animal biomass is small compared with the plant biomass. While
some animals live on the ground, most rain forest animals live in the trees. Insectivorous birds and bats fly above
the canopy; below the canopy, birds, fruit bats, and other mammals feed on leaves and fruit. In the middle zones
are arboreal mammals such as monkeys and sloths, numerous birds, insectivorous bats, insects and amphibians.
Climbing animals such as squirrels and civets, move along tree trunks, feeding from all strata. On the ground are
large mammals such as the large rodents of South America and members of the pig family. Finally small
insectivorous, carnivorous and herbivorous animals search the litter and lower tree branches for food. While
diversity is high, dominance by a particular species is low.
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Grasslands are the intermediate areas that are too dry for forests but too wet for deserts. There
are sparse trees, shrubs and bushes, and tall grass survive in sometimes harsh conditions such
as drought or wildfires; grasses can survive fires because they grow from the bottom instead of
the top. Grasslands occur in temperate and tropical areas with reduced rainfall (10-30 inches
per year) or prolonged dry seasons.
There are two types of grasslands, the tropical savanna, like the Serengeti plains of Africa, and
the temperate grassland or steppe like the prairie of the American Midwest. Grasslands are
home to large herding animals and large predators that feed on them, as well as scavengers.
There is quite a bit of diversity found among the animals living in the grassland biome. They
include those that burrow under the ground, those that graze and eat the grass, and those that
consume other animals that live in this biome. Grazers and browsers divide up resources,
eating from all different parts of the shrub or grass shoot; some eat only the tips, some eat the
middle, and some only eat new shoots or roots. Grazers eat the grass on the ground and
browsers eat the vegetation on bushes and trees. The differentiation between browsers and
grazers is one way in which ungulates (hoofed mammals) can partition food resources.
Resource partitioning, in response to competition for food, ultimately allows species to exploit
different diets and to co-exist without competing.
Zoo animals that inhabit grasslands are lion, giraffe, zebra, and prairie dogs.
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The tundra are the areas around the the two polar zones on earth; the Arctic is frozen water,
while the Antarctic is frozen land. The tundra covers the northernmost regions of North
America and Eurasia, about 20% of the Earth's land area. This biome receives about 8-10
inches of rainfall annually. Snow melt makes water plentiful during summer months. Winters
are long and dark, followed by very short summers. Water is frozen most of the time,
producing frozen soil, permafrost. The tundra is a very fragile environment.
Arctic tundra is vast open land that buts up to the frozen ocean; in summer, the tundra does
thaw and grow plants such as grass and shrubs, but its too cold for trees. There are also plenty
of patches of lichens and mosses. Dwarf woody shrubs flower and produce seeds quickly
during the short growing season. Only lichens and moss grow in Antarctica where its is mainly
ice and no soil.
A few animals highly adapted to cold live in the tundra year-round. Thick fur, blubber and
other adaptations allow animals to survive in these harsh conditions. During the summer the
tundra hosts numerous insects and migratory animals.
The zoo does not have any Antarctic species but it has Arctic species: polar bears, wolverine
and during the Christmas holiday season, reindeer.
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California is in one of the world’s five Mediterranean climate zones, characterized by mild,
wet winters and warm, dry summers. Other Mediterranean climates include lands around the
Mediterranean Sea, Chile, South Africa and Australia.
San Francisco’s frequent fog along the coast moderates the mild climate. Summer fog helps
plants to survive the dry season. At the zoo, there is a microclimate because of the coastal fog
that you might not get a few miles further east.
Adaptations of native California species include drought and fire tolerance, able to withstand
high degree of disturbance from winds and tides, and exposure to salt and sand. Spring and fall
are important growth seasons here.
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What type of adaptations might you see in a native California plant species that grows well at
the zoo?
D is correct. The San Francisco area experiences mild, wet winters and warm, dry summers.
Plants and redwoods especially are adapted for drought and fire tolerance. At the zoo plants
must be able to withstand strong winds. The Monterey cypress along the coast often become
irregular and flat-topped as a result of the strong winds that are typical of this area. Lastly
plants growing along the coast must tolerate exposure to salt and sand.
San Francisco’s frequent fog along the coast moderates the mild climate. Summer fog helps
plants to survive the dry season. At the zoo, there is a microclimate because of the coastal fog
that you might not get a few miles further east.
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Definitions:
Ecosystem: a community of living (biotic) and non-living (abiotic) things that work together.
Biome: the specific environment in which any given organism or any given population lives; biomes are
defined by their climate and dominant vegetation.
Niche: The ecological role and space that an organism fills in an ecosystem. An animal’s niche includes its
usage of resources, its unique way of life and its relationship to other biotic and abiotic factors. An animal’s
“job”.
Habitat: the specific environment in which any given organism or any given population lives. It is the
“address” of the organism. A habitat contains everything that an animal needs to survive, including air, food,
water, shelter, sun, space and other animals.
Competitive exclusion: no two species can occupy the exact same niche.
Biomass: Collective mass of the biological material derived from living, or recently living organisms in an
ecosystem at any given time.
Photosynthesis: process used by plants and other organisms to convert light energy, normally from the sun,
into chemical energy that can be later released to fuel the organisms' activities.
Food chain: the linear sequence of who eats whom in an ecosystem to obtain nutrition.
Food web: depicts feeding connections in an ecological community.
Trophic Level: the position an organism occupies in a food chain.
Producer: organisms in an ecosystem that produce biomass from inorganic compounds; they are plants.
Consumer: organisms of an food chain that receive energy by consuming other organisms.
Decomposer: organisms that break down dead or decaying organisms.
Herbivore: an animal that gets its energy from eating plants, and only plants.
Carnivore: an animal that gets its energy from eating other animals.
Omnivore: an animal that eats both plants and animals.
Frugivore: an animal that eats only fruit
Folivore: an animal that eats only leaves and stems
Insectivore: an animal that eats only insects
Browser: type of feeding where an animal eats the vegetation on bushes and trees.
Grazer: type of feeding where an animal eats the grass on the ground.
Keystone species: a species where many other species depend upon its abundance as prey for their survival.
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