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Three ways natural selection can alter variation in a population
- Directional selection: Acts against individuals at one of the phenotypic extremes.
- - Common during periods of environmental change, or migration to a different habitat.
- Disruptive selection: Favours individuals at both extremes of the phenotypic range.
- - May occur in patchy habitats.
- - Animals camouflaged on different backgrounds.
- Sexual selection: May lead to phenotypic differences between males and females (sexual dimorphism).
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Define Allopatric Speciation
The formation of new species in populations that are geographically isolated from one another.
Ex. The formation of the Grand Canyon through erosion separated widespread antelope ground squirrel species into 2 species.
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Define Sympatric Speciation
The formation of a new species in populations that live in the same geographical area.
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Pre-zygotic Mechanisms - Behavioral
- - Each species has a different mating behavior
- - Males have different wing patterns. They wave their wings in different ways which attracts the right female species.
Ex. Fruit fly species in Hawaii
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Pre-zygotic Mechanisms - Geographic
- - Where their distribution overlap, they do not interbreed.
- - Breed in different seasons of the year
Ex. Eastern and Western Spotted Skunk
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Pre-zygotic Mechanisms - Temporal Isolation
Prevents species from mating because they breed at different times
Ex. Time spotted skunks breed in different seasons
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Pre-zygotic Mechanisms - Mechanical Isolation
Prevents different species from interbreeding
Ex. Some dogs can't interbreed
Poodle and Great Dane could lead to speciation
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Define speciation
Formation of a new species
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Pre-zygotic Mechanisms - Gamete Isolation
- - Gametes come into contact, but no fertilization takes place
- - Individuals can mate, but the gametes can't meet.
- - Sperm might die, might not penetrate the egg
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Post-zygotic Mechanisms - Hybrid Viability
The development or survival of hybrids is impaired. Could die before reproducing.
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Post-zygotic Mechanisms - Hybrid Sterility
Hybrids fail to produce functional gametes
Ex. A horse and a donkey becomes a mule. The mule is sterile.
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Post-zygotic Mechanisms - Hybrid breakdown
Hybrids mate with the parent and with each other but the following generation cannot reproduce
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Define 'Niche'
An opening in the environment that the organism fills to make a living
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Define 'Habitat'
A place or environment in which an organism lives
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Define 'Ecosystem'
All the organisms in a living area along with the non-living factors with which they interact
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Define 'Community'
An assemblage of all the organisms living together and potentially interacting in a particular area
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Define 'Ecology'
The scientific study of how organisms interact with their environment
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Food Web
Plants - Grasshopper, Ground Squirrel
Grasshopper - Scorpion - Kit Fox
Ground Squirrel - Fox, Golden Eagle
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What are ‘biotic’ components of an ecosystem?
All the living things in a ecosystem
Ex. Animals, Plants, Microorganisms
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What are ‘abiotic’ components of an ecosystem?
The non-living parts of an ecosystem
Ex. Rocks, Temperature, Sunlight, Clouds
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What does a food web have?
It has an alternative food source for at least one of the species involved
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Define 'Food Web'
A network of interconnecting food chains
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Which is more stable, a food web or a food chain?
A food web is more stable because...
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What are the three major categories of organisms in an ecosystem?
1. Producers - Take energy from inorganic sources and converts them into sugars
Ex. Green Plants take energy from sun and create sugars through photosynthesis
2. Consumers - Organisms that consume energy from producers
Ex. Insects and Animals
3. Decomposers - convert detritus into vital inorganic material
Ex. Bacteria and Fungi
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What are the three categories of Consumers?
- Herbivores (feed on plants) - Deer, Sheep, Horse
- Carnivores (feed on meat) - Fox, Wolf, Lion
- Omnivores (feed on plants and animals) - Humans, Bears, Pigs
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Diagram the Carbon Cycle (biogeological cycle)
Air(atmosphere) - Carbon Dioxide(photosynthesis) - Plants(to carbon dioxide) - Carbohydrates(consumption) - Animals - Carbon Dioxide(respiration)
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What are the two categories of population regulating factors that control a population’s size and range?
- Density Independent - Limits the range of a species. Drives extinction.
- Ex. Rainfall, Sunlight, Heat
- Density Dependent - Control a population between upper and lower limits.
- Ex. Food, Predators, parasites, disease
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What are the three ecological pyramids?
Pyramid of number - number of individual organisms at different trophic levels of food chain
Biomass - amount of living organic matter at each tropical level
Energy - role the various organisms play in the transfer of energy
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What percent of the energy is lost in going from one feeding (trophic) level to the next?
10 percent
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Describe the three ways by which energy is lost at each trophic level.
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Define ‘density’
The number of individuals of a species in a given sized area
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There is a one-way flow of energy through ecosystems and that nutrients cycle around and around in ecosystems
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‘Biotic potential’
The increase in population size due to reproduction alone. Every species has the biotic potential to overrun the earth. A populations grows logistically.
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What limits population growth?
Availability of food, predation, disease, migration
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Diagram a logistic growth rate
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What does natural selection only operates on?
Traits already present
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Natural selection does not cause new mutations to occur. New mutations occur by chance.
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Discuss the Greenhouse Effect in detail and use a diagram and its labels to help with your explanation
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Discuss the three things that can happen where two species have an overlapping hybrid zone.
Reinforcement - hybrids less fit than parent species, fewer and fewer hybrids
Fusion- hybrids as fit as parents, forms single species
Stability-continued production of hybrids.
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Example of allopatric speciation in snapping shrimp
- 30 species of snapping shrimp live off the Isthmus of Panama
- Grouped into 15 pairs
- One member of each pair lives on the Atlantic side while the other lives on the Pacific side
- The geographic separation of the ancestral species of snapping shrimp led to allopatric speciation
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Define ‘carrying capacity’
The maximum number of a species that can survive in a given sized area over a prolonged period of time
-Based of food supply
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Describe what ‘biological magnification’ means and use an example in your explanation.
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Define ‘symbiosis’
Two forms of species live together in some form of interaction or interdependence
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Define 'commensalism'
One species benefits from another, the other is unaffected.
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Define 'amensalism'
One species is harmed, there is no effect on the other species
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Define 'parasitism'
One species in harmed and the other is benefited
Ex. Deer and deer tick
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Define 'predation'
One species is harmed ad the other is benefited. The host is generally killed.
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Define 'mutualism'
Both species benefit each other
Ex. termites and protozoa
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Describe the interactions between the rhino and its symbiots and name each interaction with the proper kind of symbiotic relationship.
Okpecker bird
- - picks off dead skin, ticks (Muturalism)
- - ticks on the Rhino (Parasitism)
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Describe how termites and how protozoa each benefit from their symbiotic relationship.
- Termites eat wood and the protozoa digests it.
- The protozoa are provided and shelter
- Termites digests dead protozoa and the excess glucose it provides
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What is a ‘keystone’ species?
Has a greater impact in its ecosystem than would be expected
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Discuss the three examples of keystone species that were presented in class.
Grey Wolf
Seastar
- feed on mussels, barnacles, clams, limpets
Sea Otter
- - eats sea urchins
- - sea urchins eat the hold fasts of kelp
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Why is the keystone species important?
It allows other animals to exist
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Two processes of sympatric speciation
Hybridization - hybrid is sterile, can reproduce vegetatively (runners) so a population can form.
Error in Mitosis and Meiosis - Mitosis: cells that are 2N become 4N. Flowers will have 2N chromosomes in sex cells. Isolated from parent part of the plant. Seeds will have 4N chromosomes. New species form.
New species occur when gene pods are isolated from each other.
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