Download Chapter 4 Evolution and Biodiversity A. Biodiversity is the variety of

Chapter 4
Evolution and Biodiversity
A. Biodiversity is the variety of species, genes, ecosystems, and ecosystem processes.
1. Species diversity, genetic diversity, ecosystem diversity, and functional diversity.
B. Evolution-change in a population’s genetic makeup over time; descend from ancestral
species
a. Mutations- population’s gene pool (DNA) random changes in the structure/number
of DNA molecules in a cell; beneficial changes
b. Mutations occur in two ways:
1) Gene DNA is exposed to external agents like X-rays, chemicals (mutagens), or
radioactivity.
2) Random mistakes that occur in coded genetic instructions.
C. Natural selection-members of a population have genetic traits that improve their ability to
survive and produce offspring; act on existing genes
1. For natural selection to evolve in a population, three conditions are necessary:
a. The population must have genetic variability.
b. The trait must be heritable, capable of being passed from one generation to
another.
c. The trait must enable individuals with the trait to produce more offspring than
individuals without the trait; this is differential reproduction.
2. Adaptation or adaptive traits- heritable traits that help organisms to survive and
reproduce better under prevailing environmental conditions.
3. May lead to new species because members of a population can no long reproduce.
a. Geographic isolation- physical separation (mountains, earthquake, stream, lack of
food.)
b. Reproductive isolation- isolated groups mutate and evolve to point that they can’t
reproduce fertile offspring
D. Processes: shifting of tectonic plates, volcanic eruptions, and earthquakes influence
earth’s climate and in turn affect evolution by removing and/or isolating habitats and
species.
E. Extinction- species no longer exist
1. Populations don’t adapt to environmental conditions.
2. Background Extinction- species disappear at a slow rate
3. Mass extinction - extinction rate drastically disappears; rate is relative to specific
species
F. Species diversity- change within a specific species (Ex: dogs, cats, trees); 2 types
1. Richness- number of species (oak trees, cherry trees, magnolia trees etc)
2. Evenness- abundance of each organism within a species
*Species rich communities tend to be more stable and more productive.
G. Ecological niche -species’ role in an ecosystem; factors that affects its survival and
reproduction; specific examples: amount of water, space or sunlight needed
(Habitat- where the species live; doesn’t define what the species need to survive and
reproduce)
1. Three broad Niche factors:
a. Range of tolerance for physical (trees) and chemical (nutrients) conditions
b. Interactions with other components of the ecosystem (prey vs predator)
c. Role in energy flow (sunlight) and matter (decomposers) recycling
2. Fundamental niche -full potential range of conditions and resources a species could
potentially use
3. Realized niche -part of the potential niche that allows a species to survive and avoid
competition with other species for the same resources.
(https://www.youtube.com/watch?v=-6COob_bymw)
4. Generalist species- species that have a broad ecological niche; can live in many areas;
ex: ants and rats
5. Specialist species- species that have a narrow ecological niche; can only live in very
specific areas; ex: giraffes and koala (lives in and eats the leaves of eucalyptus trees)
6. Two types of species within a niche:
a. Native species- naturally live and thrive in a specific ecosystem
b. Non-native species- species introduced into s specific ecosystem
7. Indicator species- provide early warning system to changes in ecosystem; have a
narrow range of tolerance
8. Keystone species- have a large affect on maintaining balance within an ecosystem.
a. Controls the size of a population
b. Foundation species- creates and enhances habitats that benefit other species.
Ex: corals provide a habitat to other animals
Chapter 5
Biodiversity, Species Interactions, and Population Control
A. Five basic species interactions are competition, predation, parasitism, mutualism, and
commensalism.
1. Interspecific Competition two or more species that interact to gain to the same
resource. (Ex: food, sunlight, water, soil, space, nest sites, etc)
a. Resource Partitioning- species evolve to reduce and avoid competition. Ex:
owls hunt at night
2. Predator-prey relationships –one species feed on another species; can eliminate the
sick, weak, and old; prey can avoid predation through camouflage, venom, speed,
surface adaptions (horns, protective shells etc)
3. Parasites- one organism feeds on the body or energy of another organism; host is
harmed
4. Mutualism- relationship that benefits both species; these benefits can be in dispersing
pollen and seeds for reproduction, in receiving food, or in receiving protection.
5. Commensalism- interaction that benefits one species; ex: lion and vulture
B. Populations change in size, density, and age distribution; most members of populations live
together in clumps or groups.
1. Three general patterns of population distribution occur in a habitat.
a. Clumping
i. Availability of resources varies from place to place.
ii. Living in groups offers better protection from predators.
iii. Some predator species live in packs to have a better chance of getting a meal.
iv. Temporary groups may form for mating and caring for young.
b. Uniform pattern distribution- clumps break up due to a scarce in a resource. Ex:
water.
c. Random dispersion- ex: dandelions
2. Four variables influence/govern population size: birth, death, immigration, and
emigration.
a. Increase in population occurs by birth and immigration.
b. Decrease in population occurs by death and emigration.
c. 3 reproductive stages:
i. pre-reproductive stage
ii. reproductive stage (increases population)
iii. post-reproductive stage (if this group is to large population will decrease)
3. Population is limited due to biotic and abiotic factors. Ex: light, water, nutrients,
competitors or predators.
a. Intrinsic rate of increase (r) -rate of population growth with unlimited resources;
produces a J-curve
4. Rapidly growing populations have four characteristics:
a. reproduce early in life.
b. short periods between generations.
c. long reproductive lives.
d. reproduce multiple offspring
5. Carrying capacity (K) - number of a species’ individuals that can be sustained
indefinitely in a specific space; growth decreases as resources become scarcer.
6. A population can grow rapidly with ample resources.
a. With few resource limitations, a population will have exponential growth or a Jcurve.
b. This exponential growth is converted to logistic growth when the population gets
larger and faces environmental resistance. In logistic growth, the growth rate levels off
as population size reaches or nears carrying capacity.
c. The sigmoid (s-shaped) population growth curve shows that the population size is
stable, at or near its carrying capacity.
F.
7. The density of a population may or may not affect how rapidly it can grow.
1. Density-independent population controls -affect a population’s size regardless of its
density. These are abiotic factors in the community.
2. Density-dependent population controls -have a greater affect on the population as its
density increases. Infectious disease is an example of density-dependent population
control.
8. Four general types of population fluctuations in nature are: stable, irruptive, cyclic, and
irregular.
a. Stable population -fluctuates slightly above and below carrying capacity
b. Irruptive- fairly stable population but have high peaks then a crash below carrying
capacity.
c. Cyclic- occur over a regular time period, generally a multiple-year cycle.
d. Irregular- irregular behavior attributed to chaos in the system
9. Interaction between predators and their prey
a. Top-down control- harmful effects of parasites, predators and competitors
b. Bottom-up control –limits in food supply
C. With new environmental conditions, community structures can change; one group of species
is replaced by another.
1. Ecological succession - gradual change in species composition of a given area; 2
types
a. Primary ecological succession - establishment of communities on lifeless ground;
no soil (land) and no bottom sediment (ocean); long process
i. Pioneer species -attach themselves to patches of bare rock to begin the process.
ii. Early successional plants - tiny annuals that reseed, followed by small perennial
grasses, herbs, and ferns and grow close to the ground
ii. Mid-successional plants- low shrubs and trees that require more soil and lots of
sunlight. This process takes hundreds of years.
iii. Late successional plant - generally tree species that create shade and can tolerate
shade to become a complex forest community.
b. Secondary ecological succession -establishment of communities in places with soil
or bottom sediment.
Chapter 8
Aquatic Biodiversity
A. Saltwater and freshwater aquatic zones cover about 71% of the earth’s surface.
B. Salinity of the water determines the major types of organisms found in an aquatic
environment.
C. There are four major types of organisms in aquatic systems:
1. Plankton are free-floating, weakly swimming, generally one-celled organisms. There
are three major types of plankton: phytoplankton (plant plankton), zooplankton
(animal plankton), and ultraplankton, which are no more than two micrometers wide
and are photosynthetic bacteria.
2. Ultraplankton may be responsible for as much as 70% of the primary productivity near
the ocean surface.
3. Nekton is a second group of organisms. These are fish, turtles, and whales
4. Benthos are bottom dwellers.
5. Decomposers are a fourth group. These organisms break down organic matter.
D. Three layers of aquatic life zones can be used: surface, middle, bottom.
1. Temperature, sunlight availability, dissolved oxygen, and nutrient availability
determine the type and number of producers found in these zones.
2. Euphotic zone describes the upper layer where sunlight can penetrate.
3. Dissolved oxygen levels are higher near surface due to photosynthesis in this area.
4. O2 levels are lower in deeper, dark layers due to aerobic respiration and because less
O2 gas dissolves in deeper and colder water.
5. Productivity in open oceans tends to be limited by amounts of nitrates, phosphates,
iron, and other nutrients.
6. Shallow waters are generally well supplied with nutrients for growth.
8-2 Why are marine aquatic systems important?
A. Oceans have two major life zones: the coastal zone and the open sea.
B. The coastal zone interacts with the land, and so is much affected by human activities.
1. Ecosystems in coastal zones have a high net primary productivity per unit area. They
constitute 10% of the oceans and contain 90% of all marine species.
2. There is ample sunlight, and nutrients flow from land and wind/currents distribute
them.
3. The coastal zone extends from the high-tide mark on land to the edge of the
continental shelf.
4. Estuaries and coastal wetlands are subject to tidal rhythms, runoff from land, and
seawater that mixes with freshwater and nutrients from rivers and streams.
5. Mangrove forest swamps grow in sheltered regions of tropical coasts.
6. Coastal wetlands/estuaries make nutrients available due to constant stirring of bottom
sediment.
7. These areas filter toxic pollutants and excess plant nutrients, reduce storm damage,
and provide nursery sites for aquatic species.
8. Humans are destroying/degrading these ecosystems; one-third have already been lost.
C. Organisms living in the intertidal zone have adapted ways to survive the daily changes in
wet/dry conditions and changes in salinity.
D. Barrier beaches/sandy shores are gently sloping. Organisms tunnel or burrow in the sand
to survive daily changes in conditions.
E. Low, sandy, narrow islands that form offshore from a coastline are barrier islands. They
generally run parallel to the shore.
1. The islands help protect the mainland, estuaries, and coastal wetlands from heavy
storm damage.
2. Sand is constantly shifting due to winds and parallel currents along the islands.
F. Coral reefs in shallow coastal zones of tropical and subtropical oceans support a very
diverse, complex ecosystem.
1. They grow slowly and are vulnerable to damage.
2. They thrive in clear, warm, fairly shallow water with a high salinity. The ideal water
temperature is between 18–30oC and will bleach if the water warms above this by so
much as 1oC.
3. The greatest threats today are due to sediment runoff and other human activities. Coral
reef systems may not have enough time to adapt to these rapidly changing conditions.
G. The open sea is divided into three vertical zones based primarily on penetration of light.
1. The euphotic zone is lighted, has floating phytoplankton carrying on photosynthesis,
and has low nutrient levels except at upwellings.
a. Dissolved oxygen level is high.
2. The bathyal zone is the dimly lit middle zone; no producers are in this zone.
Zooplankton and smaller fish live in this zone.
3. The abyssal zone is dark, very cold with little dissolved oxygen.
a. Organisms in this area are deposit feeders, or filter feeders.
b. Hydrothermal vents are present in some areas with specialized bacteria that feed on
chemical nutrients and are food for other organisms
c. Low average primary productivity and NPP occurs, but oceans are so large they
make the largest contribution to NPP overall.
8-3 How have human activities affected marine ecosystems?
A. Human activities are greatly affecting the ecological and economic services provided by
marine ecosystems.
1. Studies suggest 41%of the world’s ocean area has been heavily affected by human
activities.
2. About 45% of the global population lives along coasts, and that figure is expected to
rise.
3. Major threats to marine systems include coastal development, over-fishing, nonpoint and point source pollution, habitat destruction, invasive species, climate change,
and pollution.
8-4 Why are freshwater ecosystems important?
A. Freshwater life zones contain less than 1% by volume of salt. These zones include
standing (lentic) bodies—such as lakes, ponds, and wetlands—and flowing (lotic)
systems such as streams and rivers.
B. Lakes are large natural bodies of standing water found in depressions.
1. Rainfall, melting snow, and stream drainage feed lakes.
2. Generally consist of four distinct zones depending on depth and distance from shore.
a. Littoral zone is open, sunlit surface water away from shore and is the most
productive area for food and oxygen production.
b. Profundal zone is deep oven water too dark for photosynthesis. Oxygen levels are
lower.
c. Benthic zone consists of decomposers and detritus feeders. Fish swim from one
zone to another. Sediment washing and dropping detritus feed this area.
C. Stratification of water occurs in deep temperate lakes into temperature zones; no mixing
occurs.
D. During fall and spring, have turnover of water that brings up nutrients, reoxygenates
bottom levels, and evens out water temperature.
E. Lakes are described with reference to their plant nutrients.
1. An oligotrophic lake is one that has been newly formed, has a small supply of plant
nutrients.
2. A eutrophic lake has a large or excessive supply of nutrients. Typically are shallow
with murky brown or green water with low visibility and high net primary
productivity.
3. Lakes between these two extremes are called mesotrophic lakes.
F. Waters flowing from mountains to sea create different aquatic conditions and habitats.
1. Surface water does not sink into the ground.
2. Runoff is surface water that flows into streams and rivers, and the area it drains is
called a watershed or drainage basin.
G. Three aquatic life zones, each with different conditions, can be identified along stream
flow.
1. The source zone is narrow and fast moving. It dissolves large amounts of oxygen from
air, and most plants are attached to rocks. Light is available, but is not very productive.
2. The transition zone forms wider, deeper streams that flow down gentler slopes. The
water is warmer, with more nutrients, which supports more producers, but has slightly
lower dissolved oxygen.
3. The floodplain zone has wider, deeper rivers. Water temperature is warmer; less
dissolved oxygen is present and flow is slower.
H. Streams are fairly open ecosystems and receive many nutrients from surrounding lands.
I. Farms, power plants, cities, and recreation areas are often found in floodplains. This also
increases excessive nutrient input and pollutant input into the river system.
J. Inland wetlands cover the land for a part of all of each year. Wetlands include swamps,
marshes, prairie potholes, floodplains, and arctic tundra in summer.
8-5 How have human activities affected freshwater ecosystems?
A. Human activities have four major impacts on freshwater systems.
1. Dams, diversions of canals fragment ~60% of world’s large rivers and destroy
habitats.
2. Flood control dikes and levees alter rivers and destroy aquatic habitats.
3. Cities and farmlands add pollutants.