Unit 3: Biodiversity
Evolution = genetic change in population over time.
 Macroevolution - Isolation & Change in environment leads to speciation
 Microevolution: Small genetic changes that occur in a population
Types of Evolution
Coevolution – as one species evolves, its predator/prey must also evolve in order to continue the relationship (ex: flu & people)
Convergent Evolution – two species evolve to become one species – occurs when competition is too great or resources need to be
shared
Divergent Evolution – One species evolves to become to become two species
• Allopatric speciation: species formation due to physical separation of populations
• Sympatric speciation = species form from populations that become reproductively isolated within the same area
Darwin’s Theory of Natural Selection
Drives evolution & means “nature selects who lives, who dies ” (based on their adaptations)
 Nature selects the smartest, fastest, and best camouflaged to live. (these good things that help animal to survive are called
Adaptations)
 Whichever animals have the best adaptations will live and have babies (most babies will inherit good adaptations)
 Survival of the fittest: who has the most offspring that survives
4 observations of natural selection
 Overproduction- organisms have more offspring than will
survive to maturity to ensure some can pass on genes
 Variation- individuals in a population exhibit inherited
variation
 Limiting Factors limit population- it’s a struggle to survive
(competition)
 Differential Reproductive Success- best adapted breed the
most & pass on traits & new potential variation
Natural Selection can choose certain genes to be successful over others
in 3 ways
 Stabilizing Natural Selection - nature selects those with average
traits to survive, extremes die
 Disruptive Natural Selection- nature selects those with both
extremes (big & small) to survive, those with average traits die
 Directional Natural Selection - nature selects those with one extreme variation in trait to survive, average trait & other
extreme creatures die
Populations and Biodiversity
Biodiversity includes…
 Genetic diversity—genetic variability among individuals within each species
 Ecosystem diversity—variety of ecosystems (interactions between biotic & abiotic)
 Species diversity— # of different species (species richness)
o Species Richness = the # of species in a community
 varies from one habitat to another (coral reefs & rain forest = high richness)
 usually greatest at ecotone ecosystems (transition zone between 2 zones)
 The richer the community = more stable & provide more ecosystem services
Factors that INCREASE biodiversity
Factors that DECREASE biodiversity
 Physically diverse habitat
 Environmental stress
 Moderate environmental disturbance
 Large environmental disturbance
 Small variations in environmental conditions
 Extreme environmental conditions
(nutrient supply, precipitation, & temperature)
 Introduction of alien species
 Middle stages of succession
 Severe limitation of essential nutrients, habitat, or
 Evolution
other resource
o isolated islands & mountaintops have least
richness – too few niches
Ecological niches
Habitat: where an organism actually lives
Niche: what the organism’s job is in that area
 Fundamental: total range of environmental conditions that are suitable for existence without the influence of interspecific
competition or predation from other species
 Realized: the part of the fundamental niche actually occupied by the species.
o No two species can occupy the same niche at the same time.
Density-dependent factors = limiting factors whose influence is affected by population density
 Increased density increases the risk of predation and competition for mates, results in the logistic growth curve
Density-independent factors = limiting factors whose influence is not affected by population density
 Events such as floods, fires, and landslides
Species Types
Generalist – can easily adapt to environmental changes, broad niche, eat a variety of foods; live in many places;
Specialist – have a small range, narrow niche; do not adapt well; eat only a few foods; specialized reproduction
R-Strategists
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Small organisms (body size)

Large populations

Do not take care of their young

Short life span

Have many offspring

Tend to be sensitive to environmental

changes.
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Reproduce at an early age
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Quick to evolve into new species
Examples: roaches, flies,spiders, fish, etc
K-Strategists

Large organisms

Smaller populations

Take care of their young

Long life span

Few offspring

Can adapt to environmental changes

Reproduction occurs later in life
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Takes millions of years to evolve
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Examples: mammals, large trees, etc.
Survivorship Curves: Divided into 3 types based on how long an organism is expected to live.
 Type I: live a long life, die when old.(k-strategists)
 Type II: die at various ages – some live long lives, some don’t
 Type III: IF organisms live past infancy, they will live a long life (r-strategists)
Biomes of the World
Biomes: the world's major ecosystems, classified according to the predominant vegetation and characterized by adaptations of
organisms to that particular environment
 Two broad types: Terrestrial (found on land) & aquatic (water)
Terrestrial Biomes:
 Two factors that affect the type of biome present:
o Temperature & Rainfall (i.e. climate!)
 Organisms have evolved based on their environment – why some organisms are dominant in some biomes but not others.
 Most diversity is near the equator (hot & wet)
 Biomes change based on their location on earth: distance from the equator or altitude
 Vertical Zonation: how biomes change as altitude increases.
o An increase of 1,000 ft in altitude is the equivalent to moving 600 miles away from the equator
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There are different models that label biomes – depending on the book you read, there are 8 – 14 different biomes
o Nine terrestrial biomes: tundra (arctic & alpine), Taiga (boreal forest); Temperate rain forest; Deciduous forest;
Grasslands; Chaparral (scrub forest); desert (tropical & subtropical); savanna (tropical grasslands, steppe, prairie);
Tropical rain forests
Aquatic Biomes:
 Two general types based on temperature & salinity: freshwater & marine (salt water)
 Salinity increases based on
o 1) proximity to equator (hotter = saltier)
o 2) types of parent material and minerals in soil (some rocks are made of salts)
Freshwater Biomes:
 flowing-water ecosystems (rivers & streams),
 standing-water ecosystems (lakes & ponds),
 freshwater wetlands (marshes, bogs, & swamps),
 estuaries (where fresh water & salt water meet –
includes mangrove forests)
Marine Ecosystems:
 Oceans (at various levels – including deep ocean
vents)
 Coral Reefs
Energy Flow
One way flow of energy starting from sun moving to plants to consumers to decomposers to heat (2nd law thermodynamics)
 Nutrients cycle between living and nonliving world by means of energy provided ultimately by the sun.
Photosynthesis and cellular respiration
 Producers (autotrophs):make own food
 Photosynthesis: sun energy + CO2 +H2OC6H12O6 + O2
Chemosynthesis
 Consumers (heterotrophs) obtain food by eating
others
o Respiration:C6H12O6 + O2CO2 +H2O + ATP
energy
Food webs and trophic levels
Organization of organisms / Energy flow
 Herbivores (1o consumers) feed directly on producers
 Carnivores (2o, 3o consumers )feed on other consumers
 Omnivores: eat both plants/animals
 Scavengers (ex. vultures, flies, crows, hyenas) feed on dead organisms
 Detritivores (ex. worms, ants, wood beetles) feed on detritus (dead fragments and wastes of living things)
 Decomposers (fungus & bacteria) break organic dust into nutrients to enter cycles
Trophic Levels: levels of a food chain (simple chain of consumption)
Trophic Cascade = predators at high trophic levels indirectly affect populations at low trophic levels
 Keep species at intermediate trophic levels in check
Food Web – shows multiple food chains
 Typically organisms do not consume only one type of organism
 Must include arrows – pointing in the direction of energy flow
Ecological pyramids
Show trophic levels by….
 By numbers (# of organisms at each level)
 Biomass (kg of biomass per level)
 Energy (kJ or calories per level)
 Amounts tend to decrease by 5-20% at each level change (use 10% as a general rule)
Bioaccumulation: The accumulation of a substance (such as a toxic chemical) in the tissue of a living organism
 Occurs within an organism
Biomagnification: The build-up of a substance across a food web
 Particularly affects higher level consumers in the trophic levels
Species Interactions
3 Basic Types of Species Interaction
 Interspecific Competition - competition between members of two or more different species for food, space, or any other
limiting resource
 Intraspecific Competition – competition between members of the same species for food, space, mates or limiting resources
 Competitive Exclusion - similar species cannot occupy the same niche indefinitely, one species eliminates the other through
competition for limited resources
Resource Partitioning dividing up resources by using at different times, different ways, different places to reduce competition
 Owls & hawks -similar prey but hawks feed/day and owls feed/night
 Lions & leopards - similar prey, but lions/larger prey & leopards/smaller prey
Indicator species: Sensitive species that provide early warning of ecosystem problems
 Their numbers go down before other species
Keystone species – species who play a major role in the ecosystem (Ex: pollinators, top predators, etc)
Animal Relationships:
Symbiosis - relationship in which species live together in an intimate association
 Can be positive, negative, or benign for the species
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Predation one species (predator) feed directly on living organism of another species by pursuit or ambush (removes
weakest of prey from population). Since predators must assess prey during pursuit or stalking, their brains are usually larger
than prey animals
Ways to Avoid Predators:
o Camouflage
o Poison
o Chemical Warfare
o Deceptive looks & behaviors
o Travel in schools or herds
o Shells, speed, flight, smell
o Warning Coloration
o mimicry
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Commensalisms - one species benefits & host doesn’t care
o Example: Remora and shark
Amenalism: one species harmed, one species unaffected
o Hard to prove
 Example: Sheep trampling grass
Mutualism - both species benefit
o ex.nutritional mutualism
 lichens (fungus + blue-green cyanbacteria)
 legume root nodules (N2-fixing bacteria+ plant root)
Parasitism - parasite benefits & host harmed
o Example: Predator/prey
Ecological Succession
Ecological succession - natural changes & species replacement in an ecosystem over time
Climax Community: a stable mature community in a successive series which has reached equilibrium after having evolved through
stages and adapted to its environment
Resistance = community of organisms resists change and remains stable despite the disturbance
Resilience = a community changes in response to a disturbance, but later returns to its original state
 A disturbed community may never return to its original state
Primary (1o) Succession (100s-1000s of years) - succession that describes the order of plant & animal species “take-over” on new
land that starts as rock (slowly weathered into soil) due to volcanic eruption, landslides, earthquakes, severe erosion
 Bare rock is exposed.
 Since there is no soil, LICHENS are first to appear since they can live on rocks.
 Lichens SLOWLY dissolve rock into sand
 Plants die & become humus & allow rooted plants to grow
 Small plants first, then big ones take over
o Pioneer species = the first species to arrive in a primary succession
area (i.e. lichens)
Secondary (2o) Succession (decades) – succession that describes the order of plant
& animal species “take-over” on existing land (Ex: abandoned farms, parking lots,
land after a natural disaster) MUCH faster than 1o because soil is already present
 Flowers take over first
 Shrubs and bushes second
 Pine saplings return
 Park returns to climax community of tall trees and hardwoods