Chapter 6 Answers

CHAPTER 6

1.) Three characteristics that describe a biological community are physical appearance, species diversity, and niche structure.
2.) Native Species- species that normally live and thrive in a particular community. They’re important because they help balance their community and are a natural part of it.
Nonnative Species- species that migrate into or are deliberately or accidentally introduced into a community. They’re sources of income but they kill native species.
Indicator species- species that serve as early warnings of danger to a community/ecosystem.
Keystone species- species have a large affect on the types and abundances of other species in the community
3.) Interspecific competition- competition for shared/scarce resources (space, food)
Predation- predators feed on prey
Symbiosis- when a species lives off another species
Competitive exclusion principle- competiton from other species for one or more limited resources is inevitable. The fundamental niches overlap and one of the competing species must migrate, shift feeding habits, suffer population decline, or go extinct in that area
Two strategies species use to reduce competition:
1. shift feeding habits 2. migrate
4.) Two strategies predators use to capture prey:
1. pursuit and ambush 2. camouflage
Five strategies prey use to protect themselves:
1. camouflage 2. mimicry 3. chemical warfare
4. warning coloration 5. deceptive looks/behavior
5.) Parasitism- one species feeds on part of another organism (the host) usually by living on/in the host [+, -]
Mutualism- two species interact in a way that benefits both [+,+]
Commensalism- species interaction that benefits one and has little/no affect on the other [+,0]
6.) Succession- new environmental conditions can cause changes in community structure that lead to one group of species being replaced by another group
a. Primary- gradual establishment of biotic communities on newly lifeless ground. It usually takes a long time.
b. Secondary- series of communities with different species can develop in places with soil or bottom sediment
Human effects on communities:
c. Lower biodiversity
d. Increase use of earth’s NPP
e. Increase genetic resistance of pests and disease causing bacteria
f. Elimination of predators
g. Introduction of harmful species
h. Using renewable resources faster than they are replenished
i. Interfering with earth’s chemical cycling & energy flow processes
j. Relying mostly on harmful fossil fuels
7.) Birth rate- number of live births per 1,000 per year
Death rate- # of deaths/1,000/year
Immigration- people/species coming
Emigration- people/species leaving
Population change: (births + immigration) – (deaths + emigration)
8.) Limiting Factor- (light, water, nutrients) stops a population from growing infinitely
9.) Exponential Growth- starts slowly but accelerates as the population increases because the base size of the population is increasing
10.) J-shaped growth curve- (shows exponential growth) plotting the number of individuals against time
S-shaped growth curve- (logistic growth) exponential population growth followed by a steady decrease in population growth with time until the population size levels off. This yields a sigmoid/s-shape as the population with this type of growth usually fluctuates slightly above and below the carrying capacity
11.) Carrying capacity- (K) the number of individuals of a species that can be sustained indefinitely in a given space
a. Determined by limitations on the population from limited resources
12.) R-selected species- species with a capacity for high rate of population increase (r)
a. Reproduce early & put most of their energy into reproduction
b. Many, usually small offspring
c. Little/no parental care/protection
d. Opportunists- reproduce and disperse rapidly when conditions are favorable
e. Algae, bacteria, rodents, insects, annual plants
K-selected species- competitor species
f. Reproduce late in life
g. Small number of offspring with long life spans
h. Offspring develop in mothers, born large, mature slowly, and are cared for/protected by parents until their reproductive age
i. Do well in competitive conditions when population size is near K
j. Follow logistic growth curve patterns
k. Large mammals (elephants, humans, whales), birds of prey, long-lived plants
13.) Eight major ways humans have altered natural ecosystems:
a. modified, cultivated, built on, or degraded ecosystems
i. especially by using technology
b. used, wasted, or destroyed earth’s NPP that supports consumer species
c. strengthened some populations of pests and disease-causing bacteria
d. eliminated some predators
e. introduced new/nonnative species into communities
f. used some renewable resources faster than they can be replenished
g. interfere with normal chemical cycling and energy flows in ecosystems
h. human-dominated ecosystems have become more dependent on nonrenewable energy from fossil fuels

By: Dana Hansen and Jon Fusco


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( By Ranae Jabri, 5th Period, APES)

1. Three characteristics that describe a biological community are overall physical appearance (relative sizes, stratification, distribution of the population and species in each community), species diversity: the number of different species it contains(species richness) combined with the abundance of individuals within each of those species (species evenness). The last characteristic is a community's niche structure: how many ecological niches occur, and how they relate and resemble each other.

The most species-rich environments are tropical rain forests, coral reefs, the deep sea, and large tropical lakes.

2. Native species: species that normally live and thrive in a particular community.

Nonnative species: species that migrate into or are deliberately or accidentally introduced into an community.

Indicator species: species that serve as early warnings of damage to a community or an ecosystem. Example: trout disappearing when water quality is bad.(need clean water with high levels of dissolved oxygen).

Keystone species: have larger effect on the types and abundances of other species in a community than their numbers would suggest. They play critical ecological roles: pollination, top predator keystone species feed on and help regulate the populations of other species. (Examples: wolf, leopard, lion, alligator…, WHITE SHARK!)

Losing the keystone species can lead to population crashes and extinctions of other species that depend on it for certain ecological services.

Foundation Species play a major role in shaping communities by creating and enhancing their habitats in ways that benefit other species. So, elephants break and uproot trees that create forest openings in the savanna, promoting the growth of grasses.

(Some scientists think that keystone species should also include foundation species)

3. Interspecific competition: competition for shared or scarce resources such as space or food.

Ex: different animals competing for space. There is fundamental niche overlap.

Predation: when predators feed directly on all or a part of prey. They form a predator-prey relationship. Predation plays a role in evolution by natural selection by allowing successful genetic traits to become more dominant. Predators control prey populations too.

Ex: Sharks prey on fish.

Competitive exclusion principle- Competiton from other species for one or more limited resources is inevitable. The fundamental niches overlap and one of the competing species must migrate, shift feeding habits, suffer population decline, or go extinct in that area

4. Predators capture prey: herbivores swim, walk, fly up to plants that they feed on. Carnivores pursue and ambush their mobile prey. (PURSUIT AND AMBUSH). Some use camouflage to hid, then ambush. (CAMOUFLAGE THEN AMBUSH). Ex: white ermines and snowy owls hunt in snow-covered areas. Some use chemical warfare to attack prey. Ex: snakes and spiders use venom.

Prey : swim, run, fly (fast), have highly developed sense of sight or smell that alerts them to the presence of predators. Protection shells (turtles), thick bark (trees: sequoia,), spines (porcupines) and thorns (cacti and rosebushes). Camouflage (different shapes or colors or ability to change colors). They often look like other things/ background.

Chemical warfare: poisonous, irritating, foul smelling, bad tasting chemicals.

They often evolve warning coloration, that flashes “eating me is risky”.

Mimicry: look like something poisonous. Use their defense.

Behavioral strategies to avoid predation. Ex: blowfish scare off predators by puffing up, spreading their wings, mimicking a predator. Some moths: have dots like look like the eyes of a much larger animal. Some species gain protection by living in large groups (school of fish).

6. Ecological succession: gradual change in species composition of a given area because of changing environmental conditions.

Primary succession: involves the gradual establishment of biotic communities on nearly lifeless ground, takes place of thousands of years. Example: bare rock exposed by a retreating glacier or soil erosion, newly cooled lava.

Secondary succession (more common type): a series of communities with different species can develop in places containing soil or bottom sediment, places where the natural community of organisms has been disturbed, removed or destroyed. Ex: abandoned farmlands, burned/cut forests.

Human or natural disturbances can convert a particular stage or succession to an earlier one.

7. Population change= (Births + Immigration) – (Deaths + Emigration).

Capacity for growth = intrinsic rate of increase ( r) ( growth rate with infinite resources).

8. Limiting factor: availability of matter and energy resources can limit number of organisms. Ex: light, water, nutrients. Environmental resistance: all factors that act to limit the growth of a population.

9. Exponential growth: starts out slowly but then accelerates as the population increases. (J-shaped growth curve).

10. J-shaped curve is usually exponential growth. Sigmoid, S-shaped curve is logistic growth (BOOM AND BUST…SHEEP IN AUSTRALIA!) Logistic growth: exponential growth followed by a steady decrease in population with time until the population size levels off.

11. Carrying capacity (K): the number of individuals of a given species that can be sustained indefinitely in a given space. Biotic potential and environmental resistance: all factors that act to limit the growth of the population (limiting factors) determine the K.

12. R- selected species: species with a capacity for a high rate of population increase (r ). Ex: algae, bacteria, rodents, annual plants. Small offspring. Opporunists.

K-selected species, competitor, reproduce late in life and tend to have less offspring. They love long-life spans. They do well in competitive conditions where their size is near K. Ex: Elephant, larger mammals….

13. Eight major ways that humans have altered natural ecosystems:

1. Reduced biodiversity by destroying, fragmenting, degrading and simplifying wildlife habitats.

2. Used, wasted, destroyed an increasing percentage of earth’s net primary productivity that supports all consumer species (even humans. )

3. Strengthened some populations of pest species and disease-causing bacteria.

4. Eliminated some predators.

5. Deliberately or accidentally introduced new or nonnative species into communities.

6. Used some renewable resources faster than they can be regenerated.

7. Human activities interfere with the normal chemical cycling and energy flows in ecosystems.

8. Human dominated systems have become increasingly dependent on non renewable energy from fossil fuels. (Produce pollution, add to emissions).

WE NEED TO: SLOW DOWN RATES. AND THEN MAINTAIN A BALANCE.

(Ranae Jabri, 5th Period, APES)


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