Chapter 50—An Introduction to Ecology: Distribution and adaptations of organisms
Ecology: the study of the interactions between organisms and their environment
Environment includes-1)abiotic factors—non-living; like temperature, light, water, nutrients, and 2) biotic factors—all living things
Levels of organization:
Population: group of individuals of the same species living together in a particular area
Community: all the populations in a given geographic location
Ecosystem: includes the commnunity PLUS all the abiotic factors in the area.
Biomes: major types of ecosystems that are typical of a broad geographic region
Biosphere: the entire portion of the Earth inhabited by living things.
The first four categories above (temp, water, sunlight, and wind) are the major components of CLIMATE.
To see the effect of temperature and precipitation on which biome is present we can consider a climograph:
Y axis- temp x-axis- rainfall
see page 1030 for more
Rain shadow: As air hits the western slope of a mountain range (moving west to east), the air would rise to go over the mountain. It cools and thus creates rain clouds that dump the moisture. On the other side the air would sink and become warmer allowing it to hold moisture. This leads to a rain shadow, place with little rain. The Mojave desert and Gobi desert are couple of examples of this.
Terrestrial Biomes
Biome / Typical latitude / Temp. / Rainfall / Plant diversity / Animal diversity / Soil compositionTropical Rain forest / Within 23.5 degrees latitude of the equator / 23 degrees C / Abundant / Lush, extremely diverse, many vertical layers / Birds, bats, mammals, insects, very diverse / Nutrient poor
Savanna / Same as above / Varies from season to season (cool and dry, hot and dry, wet and warm) / Clear cut wet and dry seasons / Grasses and small shrubs; / Large herbivores, insects, and burrowing animals / Nutrient poor; frequent fires
Desert / Between 15 and 35 degrees / Usually warm; cool nights / Very little / Cacti and drought-resisant shrubs / Ants, birds, rodents, reptiles / Nutrient poor
Chaparral / Coastal areas between 30 and 40 degrees / Mild, rainy winters and long, hot dry summers / Varies with season / Shrubs, / Deer, birds, ants, rodents, and reptiles / Nutrient poor; short growing season, frequent fires
Temperate Grassland / Between 30 and 60 degrees / Cold winters / Seasonal droughts / grasses / Large vertebrate grazers / Very fertile; frequent fires
Temperate Deciduous Forest / Between 30 and 60 degrees / Cold winters, hot summers / Average / High diversity due to high nutrients and light, etc; Large deciduous trees / Invertebrates, rodents, deers / Nutrient rich
Taiga / Near 60 degrees; also high elevations / Cold / Varies / Conifers; spruce, pine, fir, little undergrowth / Mice,squirrels, jay, insects, deer, moose, elk, snowshoe hare / Thin, nutrient poor, and acidic
Tundra / Above 60 degrees / Cold / Usually very litle / Grasses, mosses, lichens / Insects with no wings, migratory birds, caribou / permafrost
Aquatic Biomes
1) ponds and lakes: standing bodies of water
photic zone: upper layer with light for photosynthesis
aphotic zone: below where there is not enough light for photosynthesis
Thermocline: verticle zone of rapid temperature change.
Lakes can be oligotrohic (nutrient-poor) or eutrophic (nutrient-rich)
2) Streams and rivers
Water is cold and clear at beginning and has lots of sediment near where it drains
Many plankton live attached to rocks
3) Wetlands: an area covered with water that supports aquatic plants
Filter pollutants
4) Estuaries: area where the river meets the ocean
Extremely diverse; many organism spawn here, very important both commercially and ecologically; very polluted
5) Marine ( about 3% salt)
Intertidal zone: zone where the land meets the water
Oceanic zone: regions past the continental shelf
Pelagic zone: open waters
Benthic zone: bottom of ocean
Abyssal zone: Very deepest bottoms of the ocean
INTERESTING NOTE:
WHY IS WATER SO CLEAR IN THE TROPICS?
Water is most dense at 4 degrees C. When air temp. reaches 4 degrees, the upper layer becomes as dense as the lower layer thus causing a mixing of the upper and lower layers of water. Because most of the nutrients have fallen to the lower layer, this allows much needed nutrients to reach the upper layers. The result is a bloom of growth during the spring and fall when the temp hits 4 degrees C. In the tropics, however, air temps never reach 4 degrees C, and therefore, the upper layers of water remain nutrient poor. Thus, little grows their and the water is strikingly clear!
Chapter 51: Behavior
Behavior: what an animal does and how it does it
Behavioral ecology: the study of animal behavior based on the expectation that animal’s increase their Darwinian fitness by optimal behavior
Innate Behavior:
Fixed Action Patterns (FAP): a highly stereotypical behavior that is innate
§ building webs
§ retrieving egg that falls from nest
§ blinking
- usually triggered by a set stimulus; once stimulus presented, action is carried to completion.
- Examples: 1)three-spined stickleback fish—shows agression in response to any object with a red underbelly; does not matter what shape it is 2) graylag goose—retrieves any round object outside of nest in attempt to retrieve eggs that may get loose. Will even continue to “push” imaginary egg if you take egg away while she is returning to the nest.
- FAP’s are adaptive because they prevent animal from having to develop higher level thought. Thought is expensive. Although FAP’s may sometimes cause animals to waste energy on non-sensical things, it is still “cheaper” than the price of developing and maintaining and compelx nervous system. If not, then animals adapt.
Learning:
- the modification of behavior in response to specific experiences
- habituation: loss of responsiveness to unimportant stimuli that do not provide appropriate feedback
- gray squirrels stop responding to alarm call if not followed by an actual threat
- olfactory fatigue
- put hand in cold water—eventually, it doesn’t feel cold anymore
- imprinting: a type of learned behavior with a significant innate component that occurs during a relatively short critical period. Animal is not born knowing this information, but they are born with the ability to learn it
- geese or ducks learning who their mother is
- salmon returning to the place where they were born to spawn.
- Birds learning their songs
- Humans learning a language
- classical conditioning: learning to associate an unconditioned stimulus with a conditioned response
- dog salivates in response to bell (Pavlov’s dog)
- operant conditioning: (trial and error learning) learning to associate certain behaviors with a reward or punishment and then tending to repeat or avoid that behavior.
- observational learning: the ability to learn by someone else’s trial and error
- play: the mimicking of adult behaviors in young animals without any reason; may be for practice (but the fact that they don’t get any better contradicts this) or it may be evolutionarily adaptive in that it promotes exercise and keeps muscle tone and coordination in young.
- Insight: the ability to perform a correct or appropriate behavior on the first attempt with no prior experience in that situation. If a monkey is placed in room with boxes and a banana high in the air, they will have enough insight to stack the boxes.
Other topics to consider from this chapter:
Social behavior
Migration behavior
Agonisitic behavior
Rituals
Territoriality
Dominance hierarchy
Mating behavior
Courtship
Mating systems
Polygamous, monogamous, polyandry, polygyny
Inclusive fitness
Kin selection
Coefficient of relatedness
Chapter 52: Population biology
Demography: the study of factors that affect population size
1. birth rate (fecundity): number of offspring produced per individual per given amount of time.
2. Death rate
3. Age structure: percentage of population a reproductive age, approaching reproductive age, and past reproductive age. Population will usually grow the fastest within the next generation if most of the individuals are approaching reproductive age.
4. Generation time: the faster the generation, the faster the population growth. Imagine how much more quickly the population would grow if women started having babies when they were 15 instead of 25-30.
5. Sex ratio—usually the number of females in the population is the best predictor of population growth.
Two important factors are density (number of individuals in a given area) and dispersion (the spacing of organisms within an environment).
1. Density: density is measured in several ways: you can physically count them, you can count the number per unit area and multiply, or you can use the mark-recapture method.
Mark-recapture method: Day 1—you catch and tag as many individuals in a given area as you can, keeping track of how many you catch. Day 2—you catch individuals again and count the percentage of which are marked. Then, you set up a ratio to predict the total number:
Number marked on Day 1 * Total catch on Day 2
Number of marked recaptures
Example: Day 1—catch and mark 40 grasshoppers
Day 2—catch 40 more grasshoppers; of these, 8 were tagged
Therefore, 40 is equal to 8/40 (or 1/5) of the total population.
40 = 1/5 (X)
X = 200
Your turn:
Day 1—catch and mark 70 grasshoppers
Day 2—catch 80 grasshoppers; of these 15 are marked.
What is the total population?
2. Dispersion: Within an area, organisms may be clumped, uniform, or random
Clumped: sometimes the result of resources distribution (i.e., resources are clumped); sometimes clumped for mating purposes or defence (schools of fish)
Uniform: Usually the result of competition for resources between individuals. Uniformity allows each individual to have the maximum amount of resources.
Random: result of a lack of competition; possibly found where there is an overabundance of resources. Not common in nature.
Demography: the study of factors that affect population size
6. birth rate (fecundity): number of offspring produced per individual per given amount of time.
7. Death rate
8. Age structure: percentage of population a reproductive age, approaching reproductive age, and past reproductive age. Population will usually grow the fastest within the next generation if most of the individuals are approaching reproductive age.
9. Generation time: the faster the generation, the faster the population growth. Imagine how much more quickly the population would grow if women started having babies when they were 15 instead of 25-30.
10. Sex ratio—usually the number of females in the population is the best predictor of population growth.
Strategies for leaving as many offspring as possible:
There are three extremes; each represented by a different survivorship curve. Most organisms however, fall somewhere in between.
Survivorship curve: A plot of the number of individuals born at the same general time that are still alive at each age.
Type III: Most offspring die young. The few that survive to some critical age tend to live long lives. Example: oysters—make tons of offspring which are unprotected and float around and get eaten easily. Those that manage to live long enough to find a place to live and grow a protective shell, tend to live a long time. Organisms with Type III survivorship curves usually produce many offspring at a time.
Type II: There is an equal chance of dying any time during the individual’s life. Example: Hydra—these guys are not particularly vulnerable at any time in their life. When they are born, they are practically the same as an adult.
Type I: Low death rate for young and middle aged individuals, with most organisms dying at old age. Example: Humans—Most people die when they are old. Organisms with Type I survivorship curves tend to have fewer offspring but devote resources to making sure they successfully reach adulthood.
Allocation of Resources:
Organisms do not CHOOSE which life history they want. They don’t choose the type I strategy, they don’t choose when to start reproducing (humans are a semi-exception), they don’t choose when they will die. Rather, these things are selected for evolutionarily. If an organism is born with an innate ability to produce thousands of offspring at once and that is a successful life history pattern for it, then it will leave a disproportionate number of offspring that are genetically predispositioned to also leave many offspring. Over many generations, these become the norm of the entire population.
Life history is always a trade off between energy used to survive longer and energy used to make babies. The ultimate “goal” is to make more babies that survive to make babies of their own. If you were to have ten children and tried to live off a teacher’s salary, then you may find that only a small percentage survive to reproduce on their own. You may be better off (assuming your goal is to pass on your genes) just having a few children, all of which you can afford to feed and keep healthy, etc.
Several different aspects of life history:
A. Number of reproductive episodes
1. semelparity—reproduce one time during lifetime; advantage—don’t have -to waste resources on surviving; can put almost all energy into making offspring; expected if cost of survival is high (century plant)
2. Iteroparity—reproduce several times during a lifetimes; advantage—young can be cared for until they reach maturity; expected if survival cost is low and young are unlikely to survive alone (humans)
B. Clutch Size:
1. Large clutch size—more babies, but each receives few resources and therefore, smaller percentage survive.
2. Small clutch size—fewer babies, but each receives a lot of resources and therefore, higher percentage survive.
Which works better for a given species depends on its particular circumstances.
C. Age at First Reproduction
1. Starting young—it takes up a lot of energy to reproduce (making eggs, mating rituals, courtship, nesting, rearing young) and takes away resources from adults ability to survive. Reduces lifespan.
2. Starting later—allows one to be stronger and preserve more resources to prepare for offspring; however, carries the risk that one will die before it has any offspring making all efforts to survive a waste (in evolutionary terms, fitness=0)