AP Bio: Unit 8 Ecology - Summer Homework

Stimulus

An external signal that causes a response in an organism

What do organisms respond to their environment with?

Their behaviors and physiology

Tropism

Growth toward or away from a stimulus.

* For example, sunlight is a stimulus that creates a positive tropism in plants, as they grow toward it.

Is a tropism only in plants

No, it’s also displayed in viruses, pathogens and other biological organisms

Taxis

A directed behavior toward or away from a stimulus.

* The planaria will move away from light, displaying a negative taxis.

Phototropism and Phototaxis

When light is the stimulus

Kinesis 

Random movement; not based on stimuli 

When is kinesis usually considered?

In animals and other organisms capable of random movement

Communication

An external or internal signal may cause communication behaviors between organisms, which may benefit the survival and reproductive success of a group of organisms. 

Communication Methods

* List

Visual

Tactile 

Audible

Electrical Signals

Chemical Signals

Communication Uses

* List

Indicate Dominance

Find Food

Establish Territory

Ensure Reproductive Success

Aposematic Coloration

In animals, it communicates to other species that an individual tastes bad or is poisonous

Chemical Signals

Many animals have scent glands they use to mark their territory, or they use their urine, feces, etc.

* These are also used to communicate social status and warn competitors.

Attracting Mates

* Chemical signals - Communication

Females are attracted by pheromones 

Cooperation

Behaviors that involve teamwork between individuals of the same species

What does cooperation do?

Increases fitness of individuals and survival of the population

Example of cooperation

* Fish

Schooling

* more intimidating to predators
* It may also save energy due to less drag

Example of cooperation

* Bees

Bees use a dance to tell other bees where to collect pollen and nectar

• Builders: provides home for individuals and the colony

• Heater Bees: Maintains the temperature of the colony and larva during colder months

• Worker Bees: collect pollen for queen and larva.

• Queen Bee: egg laying habits may be altered depending on the pollen that is collected

Response and Communication

* Effects on natural selection and evolution

Natural selection favors innate and learned behaviors that increase reproductive success and survival

Innate Behavior

Genetically controlled and happen without prior knowledge or experience

* Ex: all newly born mammals instinctively begin to suckle after being born.

Learned Behavior

Developed as a result of an experience

* Example: Very young ducks and geese are frightened of any shadow that moves overhead. Within a few days of hatching, the young birds find that some shadow moving overhead mean nothing. They soon habituate to these shadows and no longer try to escape from them.

Energy

Organisms use energy to grow, keep homeostasis, and reproduce

Endothermic Organisms

Maintain a constant body temperature by using thermal energy from their metabolic processes

* Ex: mammals shiver to keep warm, use heat of metabolism

Endothermic organisms examples

Mammals, birds, dinosaurs, dolphins, warm-blooded animals

Relationship between the size of an organism and its metabolic rate

Usually inverse, like in mammals.

* The smaller the size of the mammal, the higher the metabolic rate. (Remember SA to volume ratio!)

SA to volume Ratio

The amount of surface area or total exposed area of a body relative to its volume or size

* Surface area/volume

Ectothermic Organisms

Do not have the ability to internally regulate their body temperature

• They must alter their behavior to change their body temperature.

• Ex: They can group together with other animals(snakes congregating), and crawl into the sun.

Ectothermic organisms examples

Snakes, crocodiles, insects, amphibians, fish, turtles, reptiles, cold-blooded animals

What are ectothermic organisms susceptible to?

Ambient temperature

What type of organism has the greatest metabolic rate? The lowest? What’s the last type (middle)?

**Greatest:** Endotherms

**Lowest:** Unicellular Organisms

**Middle:** Ectotherms

Do all organisms have the same reproductive strategies?

No, organisms have different reproductive strategies in response to energy availability

r-selected species

Many offspring

• A small investment from the parent

• Don’t really raise their young with care, they just increase population size rapidly

Where are r-selected species common?

In areas where the environment changes more frequently and resources are scarce

K-selected species

Few Offspring

• More investment from the parent

• Care is given to each offspring

What environment are K-related species common?

Stable environments

* It’s energy efficient

Which species fluctuates around the carrying capacity?

* r-selected or K-selected

K-selected species

Reproduction rates of

• Oyster

• Fish(Tuna)

• Frog

• Hare

• Large Cat(Puma)

• Chimpanzee

From top to bottom, what does it represent?

Oyster = 5 million per year

Fish(Tuna) = 6,000 a year

Frog = 200 a year

Hare = 12 a year

Large Cat(Puma) = 2 a year

Chimpanzee = 1 every 5 years

* Top to bottom = scale from r to K-selected species   

Seasonal reproduction…

occurs at different times of the year in plants and animals

Examples of seasonal reproduction

• Plants produce pollen for sexual reproduction during the seasons when pollinators are most active.

• Animals reproduce in the spring and summer when food is most plentiful.

• Grizzly bears mate in May and July, but the female delays implantation of the fertilized egg until October or November if food is plentiful. If food is scarce, the fertilized egg is reabsorbed.

• Reproduction is triggered by a critical photoperiod (a relative length of night and daytime)

Trophic Structures

* What is it determined by?

The trophic structure of a community is determined by the feeding relationships between organisms

Trophic Levels

The positions away from the primary energy source in an ecosystem which is the sun

* links in the trophic structure

Food Chain

The transfer of food energy from plants → herbivores → carnivores → decomposers

Autotrophs

Make their own organic compounds for energy through

What are the types of autotrophs, what do they do and what’s an example?

Photoautotrophs

• Photosynthesis (uses sun energy)

• Makes inorganics to organics

• Plants & photosynthetic organisms

Chemoautotrophs

• Chemosynthesis (uses chemical energy)

• Animals living by hydrothermal vents

Heterotrophs

Must obtain their organics from another source (they consume their food).

* They metabolize carbs, lipids, and proteins through hydrolysis for energy

Length-Limiting Factor

* of a food chain

Inefficiency of energy transfer along chain - usually a food chain is only 10%(on average) efficient.

What length of food chains are the most stable?

Short food chains

Food Chain Base Structure

primary producer → primary consumer → secondary consumer → tertiary consumer → quaternary consumers

Marine Food Chain

* Basic

phytoplankton → zooplankton → carnivore → carnivore → carnivore

Terrestrial Food Chain

* Basic

plant → herbivore → carnivore → carnivore → carnivore

What do the arrows in a food chain/web represent?

Energy transfer

In a food chain what is energy lost as? How much of the energy is lost in what terms?

Energy is lost as heat

90% is lost in terms of calories

Are there more top predators or producers & primary consumers on average in an ecosystem?

More producers & primary consumers

Food Web

Two or more food chains linked together

Can a given species weave into the web at more than one trophic level?

Yes

Pyramid of Energy

• Lower levels weigh more, this is known as biomass (stored energy)

• The number of individuals = higher, lower on the pyramid

• Energy decreases as you move further up the pyramid

What tends to be true about energy pyramids?

The bottom must support the top; it doesn’t usually go past quaternary consumers

Population

A group of individuals of the same species living in the same area

Population interactions

• They interact with one another in complex ways

• They typically breed with one another more frequently than they do with those from other populations

What are adaptations in an organism related to?

Adaptations in organisms are related to obtaining and using energy in a particular environment

What does population size depend on?

A number of factors?

• Food availability

• Energy availability

Food availability

* Population size

• More Food: larger population size, higher reproduction rate, and survival rates of offspring increase.

• Less Food: smaller population size, lower reproduction rate, and survival rates of offspring decrease

Energy availability

* Population size

When energy availability in the environment changes, organisms have different adaptations

* Ex: fat storing in winter months, losing leaves when day length changes, migration

Population Growth Formula

* What does each part mean?

• dN = change in population size

• dt = change in time

• B = birth rate

• D = death rate

Exponential Growth

* When does it occur, what does it mean, what shape is it represented by

This type of growth occurs when a population grows at a constant rate when resources are abundant

• This means that the number of organisms added to the population each generation INCREASES as the population grows in size.

• The time it takes to produce offspring status is the same (often assumed to be 1 year...unless you are told otherwise)

• Represented in a J curve

Exponential Growth Formula

* What does each part mean?

dN/dt = r(max = subscript)N

• dN = change in population size

• dt = change in time

• N = population size

• rmax = maximum per capital growth rate of population = r

Population Density

Refers to how close individuals within a population live to one another

Food availability

* Population density + what does it mean

• A high abundance of food often results in a high population density,

  • This can mean a higher reproductive rate and limited space

• When food is limited, population density may decrease

  • This can mean lower reproductive rates and individuals are more spread out from one another

What cab population size be influenced by?

* Factors

Density-dependent Limiting Factors OR Density-independent Limiting Factors

Density-dependent Limiting Factors + examples

Abiotic (non-living) or biotic (living) factors that can limit a population’s size based on its density

* *Examples:* Competition for food or territory, predators, nutrient availability, parasites

Density-independent Limiting Factors + examples

Abiotic (non-living) or biotic (living) factors that can limit a population’s size regardless of its density

* *Examples:* natural disasters like floods, forest fires, volcanic eruptions, human causes (pollution)

Predator-Prey Relationships

Predator numbers have a generational lag time, and their populations will peak slightly after prey number peaks

• Density-dependent

• In a graph, after the peaks, the numbers will fluctuate around the carrying capacity

Logistic Growth Model

* What does it describe and what shape is it represented by

Describes the population growth model that begins with slow growth, immediately followed by exponential growth, and then ends with stable maximum growth that levels off

* Shown in an S curve
* Starts as a J curve until carrying capacity → population growth lowers

Carrying Capacity

Maximum number of individuals an environment can sustain

Can populations exceed the carrying capacity?

Yes, under certain conditions, populations can exceed the size of the carrying capacity and then return to normal and fluctuate around the carrying capacity

Logistic Growth Model Formula

* What does each part mean?

dN/dt = r(max = subscript)N(K - N/K)

• dN = change in population size

• dt = change in time

• N = population size

• K = carrying capacity

• rmax = maximum per capital growth rate of population = r

Community

Refers to a group of different species living together in the same location and interacting with one another; biotic factors

What are communities described based on?

Species diversity and species composition

Species Diversity

Refers to the variety of species and the quantity of individuals included in a species within a given community

Increased diversity = what?

* In terms of en ecosystem

Stability

* For example, an ocean community consists of one species of sea turtle, yet there are 15 sharks and 62 sea turtles

Which is most diverse?

• Community 1: 90A, 10B, 0C, 0D

• Community 2: 25A, 25B, 25C, 25D

• Community 3: 80A, 5B, 5C, 10D

Community 2

• Community 1: 90A, 10B, 0C, 0D; NOT CORRECT = Only 2 species

• Community 2: 25A, 25B, 25C, 25D; CORRECT = 4 species in large quantities

• Community 3: 80A, 5B, 5C, 10D; NOT CORRECT = Small quantities of species

In a community, if one species gets wiped out, there should still be ______ from the _________ of species

In a community, if one species gets wiped out, there should still be ***stability*** from the ***diversity*** of species

Species Composition

Refers to the identity of each species in the community 

* *For example,* an ocean consists of *Pomacanthus paru* and *Pomacanthus xanthometopon*; two species of angelfish

Simpson’s Diversity Index

An equation used to measure species diversity(biodiversity of a habitat)

• The higher the index value, the more diverse the community

• Based on random samples of the environment

Simpson’s Diversity Index Formula

• What does each piece mean?

• What does a value of 1 mean?

Diversity Index = ∑(n/N)²

• n = total number of organisms of a particular species

• N = total number of organisms of all species

Closer to 1 = more diversity

What do interactions among populations determine?

How they access energy and matter

Do communities change over time depending on interactions between populations

Yes

Competition

An interaction that can affect how populations access energy and matter

• Can result in a change in community structure

• Can occur within or between species

• Competition for food and habitats

Interactions between species can be…

positive, negative or neutral

Symbiotic Relationships

A close, prolonged association between two or more different biological species

• Mutualism

• Commensalism

• Parasitism

Positive Species Interactions

• Mutualism: both species benefit (+/+)

• Commensalism: one species benefits but the other is not harmed nor helped (+/o)

Negative Species Interactions

• Predator-Prey: one species uses the other as a food source (+/-)

• Parasitism: one species benefits at the harm of another (+/-)

Neutral Species Interactions

* Have no impact on the species involved
* Example, deer and rabbits living in a forest (o/o)

Bracket or shelf fungi as tree parasites

• They produce fruiting bodies that grow on the bark of the tree

• They absorb nutrients from the outer bark of the tree

  • Can cause weakening of the external structure of the three

    • Reduced canopy and foliage density

      • Frees up resources

  • Can infect the interior parts of the tree

    • Branches of entire tree may rot and fall

      • Provides new available niches and habitats

• They provide microhabitats for insects and other organisms

  • Insects can live in the holes the fungi make in the tree bark

• They provide a food source for insects and other organisms

  • Some insects use the fungi as a food source

Niche Partitioning

Refers to a decrease in competition over limited resources between two similar species because each species is accessing the resource in different ways

Niche

Everything that an organism does; it’s job

Can organisms occupy the same niche?

Nope, no two species have the same niche; they may be close but they tend be at least slightly different in a well established ecosystem

What can disruption cause in a food chain?

A negative cascade of effects

Trophic Cascade

Refers to the negative effect the removal of or decrease in a key species has on other trophic levels

What can a population experience with the removal of a key species? What results from this?

Populations can experience exponential growth or death with the removal of a key species

* Results in the interruption of the flow of energy through the ecosystem and resource availability