Unit 4

Chapters 4 and 5

ecological niche- species way of life in a community• What job does it do or role does it fulfill?• The Alligator is a:• Keystone species- A species in an ecosystem that plays a

central role in the health of that ecosystem, and whose removal may cause the collapse of the ecosystem

The American Alligator-

Biodiversity or Biological diversity

• The variety of the Earth’s species, the genes they contain, the ecosystems in which they live, and the ecosystem processes such as energy flow and nutrient cycling that sustain all life

• Interaction between speciation and extinction

Why is biodiversity important?

• Food• Wood• Fibers• Energy• Medicines• Preserving air, water, and fertile soil

Natural selection- independently proposed by:

• Charles Darwin• Alfred Wallace

Observations that led to concept of evolution

• Organisms struggle • Some individuals have advantages that help them

survive• The ones that survive, pass these traits down to

offspring• Natural selection• A change in the genetic characteristics of a population

from one generation to another is biological evolution

Genetic variability is the first step

• Occur through mutations• Only mutations in reproductive cells are passed down• Mutagens are external agents that cause mutations, but

mutations can occur randomly( examples: chemicals, UV light, radioactivity, Xrays)

• Adaptation or adaptive trait- any heritable trait that enables an individual to survive

• In order for natural selection to occur, a trait must be heritable, meaning that it can be passed down from one generation to another. The trait must also lead to differential reproduction.

Summary of biological evolution

• Genes mutate, individuals are selected, and populations evolve that are better adapted to survive and reproduce under existing environmental conditions.

Possible futures

• Adapt

• Migrate

• Become extinct

Adaptations of humans that have made them successful

• Strong opposable thumbs

• Walk upright

• Complex brain

Limits to natural selection

• Adaptations only occur for traits already present in a populations gene pool.

• Even if a beneficial heritable trait is present in a population, the population's ability to adapt may be limited by reproductive capacity

Common myths

• Survival of the fittest- does not mean survival of the strongest- ****** fitness is a matter of reproductive success*****

• Organisms do not develop traits because they need or want them

• Grand plan of nature

Effects of plate tectonics

• 1. Locations of continents influences climate which helps determine where plants and animals can live

• 2. The movement of continents has allowed species to move, adapt and form new species through natural selection

speciation

• Geographic isolation• Reproductive isolation

Extinction is forever

• Golden toad- endemic to costa rica • Extinction due to climate change

Background and mass extinction

• Background rate of extinction- normal low rate of extinction throughout history- 1 to 5 species per million species

• Mass extinction- loss of many species in a short amount of time

• 25%-70%• 5 mass extinctions have occurred in the last 500 million

years.

Species richness- number of different species

Species evenness- abundance of individuals of each species

Geographical location

• Terrestrial- higher diversity in tropics• Most diversity in rainforest, coral reefs, the ocean bottom

zone and large tropical lakes

• Species rich ecosystems are more productive and stable due to higher numbers of different producers with more feeding relationships

Each species has a distinct role to play in in an ecosystem

• ecological niche- species way of life in a community

Generalist vs. Specialist species

• A generalist species has a broad niche(live in many places, eat a variety of food, tolerate a wide range of conditions)(Ex. Flies, roaches, mice, rats, white-tailed deer, raccoons, and humans)

• A specialist species has a narrow niche(one types of habitat, one or few types of food)(tiger salamanders, giant pandas)

• Which is better? It depends, When conditions are stable, generalists are better off. When conditions are rapidly changing, specialists do better

Cockroaches: nature’s ultimate survivor

• 3,500 species, eat almost anything, live almost anywhere, avoid predators, High reproductive rates, quick genetic resistance,

Non-native species

• A.K.A.- invasive, alien, exotic

• They can spread rapidly if they do not have predators and diseases they faced before, or they may be able to out-compete native species

Biological smoke alarms

• They provide early warnings of damage to a community or an ecosystem.

factors that can affect frogs and other amphibians at

various points in their life cycles

• Habitat loss and fragmentation• Prolonged drought• Polution• Increases in UV radiation• Parasites• Viral and fungal diseases• Climate change• Overhunting• Natural immigration of, or introduction of nonnative

predators and competitors

Why should we care about amphibians?

• Sensitive biological indicators• Important ecological roles in biological

communities• Genetic storehouse of pharmaceutical products

waiting to be discovered.

Keystone species

• Pollination• Top predator

Foundation species-

• Examples- elephants, beavers

• What’s the difference between a keystone and a foundation species?

• Foundation species help to create habitats and ecosystems

• Keystone species do this and more

Ch 5 notes• Sea otters generate millions of dollars in tourism. • Keystone species that helps maintain kelp forests to

maintain biodiversity.• 5 types of species interactions-

• Interspecific competition• Predation• Parasitism• Mutualism• Commensalism

Illustrates the principle of population control

Competitive exclusion principle

• No two species can occupy exactly the same ecological niche for very long

• Methods of capturing prey• Carnivores- pursuit and ambush• Camouflage• Chemical warfare

How prey avoid predators

• Speed, developed sense of sight or smell, protective shells, thick bark, spines, thorns, camouflage, bright coloring, chemical warfare, warning coloration,

E.O. Wilson

• If it’s small and strikingly beautiful, it’s probably poisonous.

• If it’s strikingly beautiful and easy to catch, it’s probably deadly.

Coevolution

• Predators and prey constantly exert intense natural selection pressures on each other.

Parasitism- one benefits the other is harmed

parasitism

Mutualism- both benefit

mutualism

Commensalism- one benefits, the other is not helped or harmed

Reducing niche overlap

• Resource partitioning- when species competing for similar scarce resources evolve specialized traits that allow them to use shared resources at different times, in different ways, or in different places.

Population distribution

• Even• Random• Clumped

• Clumped is the most common because resources are often found in patches

Population change

• Population change = (births + immigrations) – (deaths + emmigration)

• Intrinsic rate of increase- reproduce early in life, have short generation times, can reproduce many times, and have many offspring each time

• When a population exceeds carrying capacity, the population can crash.

• Overshoot occurs because of reproductive lag time.

K- selected and r-selected

• r-selected species have a capacity for a high rate of population increase, they produce many offspring to try to overcome huge losses when offspring are young (they have boom and bust cycles of population growth)

• K-selected- long life spans, reproduce later in life, small number of offspring, cared for by parents

Genetic factors that play a role in loss of genetic diversity

• Founder effect- occurs when a few individuals in a population colonize a new habitat that is geographically isolated from other members of the population.

• Demographic bottleneck- when only a few individuals survive a catastrophe such as a fire or hurricane

• Genetic drift- random changes in the gene frequencies in a population that can lead to unequal reproductive success

• Inbreeding- when individuals in a small population mate with one another

Density dependent population controls

• Competition for resources, disease, predation, parasitism

Density independent

• Floods, fire, hurricanes, pollution, drought, habitat destruction

Four general patterns of variations in population size?

• 1. Stable- fluctuates near carrying capacity

• 2. Irruptive- grows to a high peak and then crash to a more stable lower level

• 3. Cyclic(boom and bust)- populations rise and fall every so many years

• 4. Irregular- no recurring pattern

Ecological succession

• The gradual change in species composition in a given area.

• Primary succession- happens where no previous ecosystem has existed (exposed rock from a receding glacier)

resilience

• The ability of a living system to be restored after a period of moderate disturbance

Tipping point

• Ecosystems and global systems have limits to the stresses they can take. The level beyond which any additional stress will cause an abrupt and unpredictable change