Unit B
Ecosystems & Population Change
Interactions within
Ecosystems
• Ecosystem- is a community and its physical and chemical environment.
• Examples of different ecosystems
• Terrestrial ecosystems
– (e.g. Prairie, grassland, forest…….)
• Aquatic ecosystems
– (e.g. Pond, lake, stream…….)
• Ecosystems rarely have sharp boundaries,
– organisms can move back and forth from one ecosystem to another.
• This area between ecosystems is where organisms from both ecosystems interact with each other.
• Ecotones – a transition area between
ecosystems
• These transition areas or ecotones contain
species from both bordering ecosystems,
so they often contain greater biodiversity
than either ecosystem.
Describe why ecotones tend to be less fragile
How do ecotones guard against extinction?
• Ecosystems with greater biodiversity tend to be less fragile.
• For example if a predator has to rely on a single species as a food source, its very existence is tied to the survival of the prey.
• In ecotones and other diverse areas there are more species, and a predator may
have an alternative prey if something
happens to the population of its main prey.
Roles in Ecosystems
• Each organism has its own place within an ecosystem.
• Ecological niche – an organism’s role in an ecosystem, consisting of its place in the
food web, its habitat, it’s breeding area and time of day at which it is most active.
– Everything it does to SURVIVE and REPRODUCE.
• Each species in an ecosystem tends to have a different niche, a different role to play.
– This helps to reduce competition between species.
• E.g. Even if two species eat the same food they are not in competition because they may:
– Live in different places – Eat at different times
Roles in Ecosystems
• E.g. Owls and hawks feed on many of the same organisms, but occupy distinctly different niches.
• Owls hunt down prey with in forests
• Hawk hunt down prey in grassland and open fields
• Owls are active during dusk and at night
• Hawk hunt by daylight
• Competition is further reduced because owls and hawks nest in different areas.
Competition for Niches
• When a new species enter an ecosystem, it causes a disturbance because it comes into competition for a niche with one or more of the species already in the ecosystem.
• Exotic species – species that are not native to an ecosystem
• The introduction of new species happens
naturally. Animals are mobile and can move from one ecosystem to another.
Introduction of Exotic species
• The introduction of new species by
humans to an ecosystem is one of the main causes of species depletion and extinction, second only to habitat loss.
• Problems with introducing Exotic Species:
• No natural population controls (predators or diseases)
• Native species may not b able to compete for space, food or reproductive sites.
• Prey organisms may not have defense mechanisms.
Introduction of Exotic species
• The actual number of introduced species that have established themselves in
Canada is well over 300 species.
Terrestrial and Aquatic
Ecosystems
• Ecosystems are smaller regions in the biosphere.
• Complexity of ecosystems varies,
depending not only on the organisms that live in them but also on abiotic factors
such as climate and local geology.
Define a Biome
• Biome is a large geographical region with a specific climate, and the plants and
animals that are adapted to that climate.
• Canada has four major Biomes:
1. Tundra 2. Taiga
3. Temperate deciduous forest 4. Grassland
Terrestrial Ecosystems
• Found anywhere on earth not covered by water
• Alberta has four major terrestrial ecosystems
– Taiga – Muskeg – Grassland
– Deciduous Forest
• Identify the Abiotic and Biotic factors that contribute to the creation of Albertan
Terrestrial Ecosystems.
Factors Affecting Terrestrial
Ecosystems
Each ecosystem is defined not only by the organisms that live in it but also by the abiotic
factors that affect them.
1. Soil
• Soil can be viewed as a series of layers
1. Litter (upper layer) – partially decomposed leaves/grasses
2. Topsoil (under litter)– small particles of rock
mixed with decaying plant & animal matter called humus
3. Subsoil (under topsoil) – more rock particles with only small amounts of organic matter.
4. Bedrock (beneath soil) – composed of rocks
• Quantity of each layer will affect ecosystem productivity
• Quality of soil can also affect productivity
– E.g. pH, human impact
2. Available Water
• All organisms depend on water to live
• Determined by:
– Precipitation (rain, snow, etc.) – Duration it stays in the soil
– How much is collected beneath soil
3. Temperature
• Organisms are able to adapt to temperature fluctuations
– i.e. Trees in Alberta can keep their leaves during winter (coniferous trees) to better survive a short growing season.
– They do not have to spend time & energy &
nutrients on growing new leaves.
• Organisms can also migrate or hibernate to escape undesired temperatures
– i.e. some birds (loons) migrate to warmer climates in the winter.
– i.e. bears hibernate during winter
4. Sunlight
• Sunlight vary between different ecosystems
– i.e. Less sunlight during winter in Canada vs in Jamaica
• Sunlight can also vary within the ecosystem
– i.e. Less sunlight during winter in Canada vs during summer in Canada
Factors Affecting
Aquatic Ecosystems
1. Chemical Environment
• Freshwater vs saltwater
• Amount of dissolved substance, such as phosphorus, nitrogen, pollutants
• Amount of dissolved oxygen
– Which depends on temperature, pressure (depth of water), and amount of salt & other dissolved substances
2. Temperature and Sunlight
• Affected by depth of water as well as the seasons
– Ecosystems near the surface will get more light and warmer temperatures
3. Water Pressure
• Water is 800 times denser then air
– Hard to move through!
• Water pressure increases then you move
deeper into the water body
4. Seasonal Variations
• As water cools, it becomes more dense
until it reaches 4 degrees Celsius…then it
becomes less dense!
• Winter
– Ice/snow covers lakes and acts as insulators – Therefore, environment underneath the ice is
very stable, even if it gets colder above the ice.
• Spring
– Oxygen can now pass from air into water
• Summer
– Upper level of lake (epilimnion) warms up
– Lower level of lake (hypolimnion) remains at low temperature
– Middle level of lake (thermocline) drops in temperature from warm to cold
• Fall
– Water goes from warm to cool and sinks to bottom.
This rotates oxygen levels to the bottom of the lake.
Limits on
Populations &
Communities
Biotic Potential
• Biotic Potential – The Maximum number of offspring that a species could produce with unlimited resources
• Biotic potential is regulated by four
important factors:
Limiting Factors
• Factors in the environment can prevent pollutions from attaining their biotic
potential.
• Any resource that is in short supply is a limiting factor on a population.
• Food
• Water
• Territory
• Presence of pollutants and other toxic chemicals
Carrying Capacity
• Populations commonly fluctuate because of an interaction of the many biotic and abiotic limiting factors.
• Ecosystem is stable when none of the
populations exceeds the carrying capacity.
Carrying Capacity
• Carrying capacity- the maximum number of individuals of a species that can be
supported by an ecosystem.
• Carrying capacity for any species is
determined by the availability of resources (food, water)
• Populations can exceed the carrying
capacity of the ecosystem, but not for
long.
Limits of Tolerance
• Carrying capacity for any species is
determined by the availability of resources (food, water)
• Populations can exceed the carrying
capacity of the ecosystem, but not for
long.
• Organism’s can survive within a certain range of an abiotic factor
• Above and below the range it cannot survive.
– Example: Temperature
• Law of Tolerance – states that an
organism can survive within a particular range of an abiotic factor.
• Law of the minimum- states that the
nutrient in the least supply is the one that
limits growth.
• The number of organisms in an ecosystem is important when considering the effects of some abiotic and biotic factors.
• Population is said to be dense when there
is a large number of organisms in a small
area.
Factors that cause changes in populations
– Density-independent factors – a factor in an ecosystem that affects members of a population regardless of population density.
– Density-dependent factors – a factor in an
ecosystem that affects members of a population because of the population density.
Changes in Ecosystems
CLASSIFICATION
The value of classifying organisms includes:
1. To understand the complex variety of living things
2. The use of data about common structural features assist in identifying organisms
3. Enables prediction of characteristics shared by members of a group
4. Shows evolutionary links; the evolutionary history of a species or a group of related
species (phylogeny)
Taxonomy
• Taxonomy is the science of classification
according to inferred relationships among
organisms
The binomial system of nomenclature is a system of naming organisms developed by Carolus Linnaeus.
– “Binomial” – Two part Latin scientific name.
• The first part is the genus (pl. genera)
• The second part is the descriptive name or species
– Each genus can include many species of related organisms
• Felis sylvestris is the domestic cat
• Felis lynx is the lynx
– Rules or nomenclature:
• Genus and species are italicized (or underlined if handwritten)
• All taxa from the genus level and higher are capitalized
Levels of Classification
• Classification recognizes seven levels in the hierarchy of taxa:
– Kingdom – Phylum – Class – Order – Family – Genus – Species
• The filing system groups species into a hierarchy of increasingly general
categories.
– Similar species are grouped in the same genus
– Similar genera are grouped in to the same family
– Families are grouped into orders – Orders are grouped into phyla
– Phyla are grouped into kingdoms
• Each taxonomic level is more inclusive than the one below.
– The more closely related two species are, the more levels they share.
• Now let’s go through a couple examples
together…
Cabbage white
butterfly
Human White dead nettle
KINGDOM Animalia Animalia Plantae
PHYLUM Arthropoda Chordata Angiospermophyta CLASS Insecta Mammalia Dicotyledonous
ORDER Lepidoptera Primates Tubiflorae FAMILY Pieridae Hominidae Labiatae
GENUS Pieris Homo Lamium
SPECIES brassicae sapiens album
Domestic Cat
Bobcat Lion Dog
KINGDOM Animalia Animalia Animalia Animalia PHYLUM Chordata Chordata Chordata Chordata CLASS Mammalia Mammalia Mammalia Mammalia ORDER Carnivora Carnivora Carnivora Carnivora FAMILY Felidae Felidae Felidae Canidae
GENUS Felis Felis Panthera Canis
SPECIES silvestris rufus leo familiaris
• Today most scientists believe that organisms have changed over time.
• Phylogeny is the history of evolution of an organism
• Relationships are shown in a diagram called a phylogenic tree
– Starts from oldest (most ancestral) form and branches off to descendants.
Current Phylogeni c tree
How do we classify?
• Dichotomous key
– Means two forks
Dichotomous Key Template Chart
1 a.
b.
Go to 2 Go to 3
2 a.
b.
3 a.
b.
4 a.
b.
5 a.
b.
6 a.
b.
7 a.
b.
Dichotomous Key
2: Killer, 3: Humpback. 4: Beluga,
5: Narwhal, 6: sperm whale, 7: blue whale, 8: bowhead
Analysis
a) plates or teeth, presence of a dorsal fin, length of pectoral fin, nose size, mouth position
b) To indentify various organism c) Answers may vary
d) Tail, food source, habitat, etc.
Evolution
Adaptation and Change
Define the concept of evolution
• Evolution is the process by which
populations of living things change over a series of generations.
• Evolution does not refer to individual change or development
• Evolution occurs within a population of
organisms
ADAPTATION AND CHANGE POPULATIONS
• Adaptation
· a change in characteristic of an
organism which increases its chances of survival.
· Variation in a trait may give adaptive advantage to a species
EVIDENCE OF
EVOLUTIONARY CHANGE
· Evolution: The process by which populations of living things change over a series of generations
· Direct Evidence:
· Fossils
· Earth’s History
· Biogeography
· Radiometric dating
– Indirect Evidence
• Comparative Anatomy
• Homologous structures
• Analogous structures
• Embryology
• Vestigial Organs
• Physiology
• Biochemical Evidence
Direct Evidence for Evolution
• Fossils: the remains,
impressions, and traces
of organisms from past
geological ages
Geological History
Fossil Formation
Fossilization occurs in many ways
· Organic components of the organism are replaced by minerals.
· Impressions left by organisms are
preserved by the solidification of mud.
· Organisms can sometimes be caught in amber and preserved
– Mammoths, bison and other extinct mammals have been found frozen in Arctic ice.
– Acidic Bogs-conditions retard decomposition
Dating the Past
• Radioactive decay provides scientists with a way of determining how old the Earth is
• Using decay rates in units called half lives physicists can determine the age of a
specimen
• Radiometric dating is a technique used by
paleontologists to determine the age of a
rock or fossil
Evidence from Biogeography
• Biogeography is the study of the
geographic distribution of life on Earth
• Earth’s landmasses have undergone great change over time
• Fossils of the same species have been
found in different continents suggesting
the continents were once joined
Biogeography
• Fossils younger than 150 million years old are not found on different continents
suggesting they evolved after the breakup.
• Evidence from Biogeography suggests that different species evolved
independently in isolated parts of the world
Movie Time!
• Macroevolution – Introduction to Mass Extinction.
• 12:03 – Blast from the Past
• 18:47- Beginnings
Indirect Evidence:
Living Organisms
Embryology
• the study of
organism in the early stages of
development
• offers valuable insight into the
process of evolution.
Embryology
Homologous Structures
Homologous structures
• Have similar origin but different uses in
different species.
Homologous Structures
• Formed from DIVERGENT EVOLUTION
– development of different
forms or structures in related species due to adaptation to different environments.
– Ex: brown bear are
predominantly vegetarian, while the polar are
carnivores.
Divergent Evolution
Same Ancestor
Different Body Form
Different
Environments
Vestigial Organs
• Anatomical structures that serve no purpose
– Snakes and whales have vestigial hip and leg bones
• Suggests they evolved from
ancestors that
walked on four
limbs
Analogous Structures
Analogous
structures are
similar in function and appearance
but came from different
ancestors.
Indirect Evidence For Evolution
• Analogous structures
· Structures which are similar in function and appearance but came from different
ancestors.
· Examples: wing of an insect and a bird
– Good indicators that these organisms did not evolve from a common ancestor
Analogous Structures
– Illustrates
CONVERGANT EVOLUTION
• development of similar forms from unrelated species due to adaptation to similar
environment
• Ex: the torpedo shape of
dolphins and sharks. Over time, the two began to look more and more alike.
Biochemical Evidence
– Analysis of chemicals can be used to show evolution
– Similar proteins in species diversify as evolution takes place
– DNA and cytochrome enzyme C (respiration) are similar in all organisms
– DNA analysis-used determine how closely related organisms are
· suggest a common ancestor
Biochemical Evidence
• Similar
chemicals in cells suggest common
ancestors
• Eg.
Respiratory
enzymes and
insulin
Biology 20
THEORIES AND MECHANISMS OF
EVOLUTION
Theories of Evolution
Lamarck -- 1801
Two Theories on Evolution:
Lamarck vs. Darwin
Lamarck
• Key Factor-Environment
• Theory of Need: Organisms change because they need to change.
– For example: Because the environment
changed, the ancestor of the snake needed to squeeze through narrow spaces so it
stretched its body and began to crawl.
– I guess his legs got scraped off!!
Lamarck
• Theory of Use and Disuse: Use-remains strong. Disuse-weakens and disappears.
For example snakes legs.
• Theory of Passing on Acquired Traits: Traits acquired in life time could be passed on to offspring.
• Nice try Lamarck but acquired traits can't be inherited. Too bad, So Sad!
Darwin's
Theory of Natural Selection
• 1859-Book called The Origin of Species explained a theory of how species
developed
• Darwin explained that evolution occurs in five steps:
– Overproduction
– Struggle for existence – Variation
– Survival of the fittest – Origin of new species
Darwin’s Famous Journey
• Darwin sailed around the world as a naturalist on the HMS Beagle at the age of 22.
On his trip, he was especially surprised by the unusual
species along the coast of South America (the
Galapagos Islands)
• Of particular interest to
Darwin was the 14 varieties of finch that were similar to each other in many ways and to finches found on the
mainland
Darwin’s Finches
• Most notable difference in the finches lay in the shape of their beaks...
• The different beak shapes were
ADAPTATIONS for eating a certain kind of food characteristic to the geographic
locations where the finches were found!
Darwin’s Finches
• Darwin assumed
that these different species of the
same bird evolved from a common
ancestor from the mainland...
Adaptations
remained in gene
pool out of need!
Darwin’s Finches: Divergent Evolution
These finches came from a
common ancestor that had a particular
beak shape.
When the birds migrated to different parts
of the Galapagos Islands, their
beaks had to adapt to the
new
environment in order for them
to be able to eat!!!
Overproduction (Darwin)
• The number of offspring produced by a species is more than can actually
survive.
• Example:
– A single fern produces 50 million spores per year.
– If each of these spores would thrive and survive, in only two generations ferns
would cover North America.
Struggle For Existence (Darwin)
• Every living organism faces a constant struggle to survive.
• Only a fraction of offspring will survive due to fierce competition for
– food – shelter
More on Darwin’s Theory
• Variation:
– Individuals of a given species vary.
– Only identical twin are the same.
• Survival of the fittest (Natural Selection):
– Nature selects which organisms which will survive based on traits that give them an advantage in the environment.
A New Species
• Origin of new species:
– The organisms that survive and pass on traits to offspring.
– This leads to Speciation
Comparison of
Lamarck and Darwin
Darwin
• Organism vary regardless of the environment
• The environment then determines whether a variation is harmful
(die) or helpful (survive)
Lamarck
• Individuals change to suit their environment
• Change is based on the need or “want” to change
Sources of Inherited Variation
• Variation is the differences among individuals within a population
– Variation can be beneficial, neutral or harmful depending on the type.
– Variation contributes to evolution
because of a concept called selective
advantage
• Selective Advantage
– is the characteristic of an organism that enables it to survive and reproduce better than other organisms in a population in a given environment
– The two main sources of genetic variation are mutations and the genetic shuffling that
results from sexual reproduction
Mutations
- any change in a sequence of DNA - occur because of mistakes in the replication of DNA
Gene Shuffling
- occur during the production of sex cells
• Natural selection on certain traits can lead to changes in trait frequencies and thus to evolution.
• Beneficial mutations may increase the
fitness and
reproductive success of an individual and therefore will become more common in a
population. These traits are selected for
Speciation and Evolution
• Speciation is the formation of a new
species through reproductively isolation
• This isolation could happen in two ways:
Behavioral isolation: when two populations are capable of interbreeding, but have
differences in courtship rituals
Geographic isolation: two populations are
separated by geographic barriers such
as rivers or mountains
Fact
• horse/donkey hybrids are popular for their durability and vigor.
• While different species of the Equidae family can interbreed, offspring are almost always sterile.
• A male donkey or ass is called a jack, a female a jenny
• A mule is the offspring of a jack (male) donkey and a mare (female horse).
• The much rarer successful mating of a male horse and a female donkey produces a hinny.