01 Ecology and Populations

What is ecology? What type of research questions do ecologists attempt to answer?
-Ecology is the study of living organisms and their homes (environments).
-Ecologists study interactions between organisms and their environments.
-Not equal to environmentalists→an advocate, drive policy and get action.

What are abiotic components of an organism’s environment? What are biotic components?
Abiotic: not living, warmth, heat, temperature, moisture, nutrients, nonliving chemical and physical traits

Biotic: the living things that shape an ecosystem. Any living component that affects another organism.
1. Competitors -/-
2. Predators (include parasites) +/-
3. Mutualists +/+
4. Commensalism +/0

Define and contrast the following: organismal ecology, population ecology, community
ecology, ecosystem ecology, landscape ecology.
Organismal Ecology: study of the morphological, physiological, and behavioral ways in which individual organisms interact

Ex. When does an individual eat over a day?

Population Ecology: how do the numbers of a population increase/decrease over time. The study of populations in relation to the environment.

Ex. When is it a good time to catch crabs?

Community Ecology: how do species interact in a shared space? A community is multiple species sharing space.

Ex. In a forest, one species of tree competing with another species of trees

Ecosystem Ecology: Management of resources.

Ex. How ecosystems work and relates this to their components such as chemicals, bedrock, soil, plants, and animals.

Landscape Ecology: Application in management and development

Ex. How humans use their environments.

Pattern: becomes larger in scale

What are factors that affect an organism’s distribution? What is the name of the field of study
that seeks to explain the past and present distribution of individual species?
1. Dispersal- seeds can’t move to that area
2. Behavior- selection of habitat
3. Biotic factors- Predation, parasitism, competition, disease
4. Abiotic factors-
a. Chemical factors: salinity, pH, soil nutrients
n. Physical factors: temperature, light, soil structure

Biogeography- the field of study
that seeks to explain the past and present distribution of individual species?

What is a biome? List and describe the aquatic biomes. List and describe the terrestrial biomes.
Biome: defined by similar climate and the communities of plants, animals, and soil organisms

Aquatic Biomes:
Marine systems: 3% salt
Freshwater systems: 1% salt
1. Streams and Rivers: move and are connected to natural terrestrial environments
2. Wetlands: where water meets land and stays for a while
3. Estuaries: place where salt water and fresh water meet (the bay)
4. Seas/oceans
5. Lakes
Terrestrial Biomes:
1. Tropical forests: Layers: understory, mid, and top canopy. Adaptations:
Epiphites: a plant that lives on another plant (epiphites can be a parasites)
2. Savannas: grasslands with scattered treee
3. Deserts: low rainfall, hot, animals are nocturnal, adapted for water retention
4. Chaparral: Dry hot summer, wet wild winters.
Usually disturbed by fire. Wipes the slate clean. Bushes take over and underground growth begins.
5. Temperate grassland: Occasional fires/ seasonal droughts.
Used for grazing and agriculture
6. Temperate deciduous forest: cold winter, preciptation of ice and snow, water not available in the form that is loose and running. tree go dormant
7. coniferous forests: Gymnosperms, tree with cones. Redwoods, conifers. Conifer needles (dealing with cold, reduce surface area)
8. Tundra: a cold desert, has permafrost that limits growth of plants

What are the main components of climate?
-The prevailing weather patterns for a given region
1. Temperature
2. Water
3. Wind
4. Light

What is the relationship between environmentalism and ecology?
Ecologists are not environmentalists→an advocate, drive policy and get action.
Ecologists study environment interactions.
Environmentalists are concerned with natural resources, deforestation, and ecological disasters.

What are some practical reasons for studying species distributions?
Distribution: where organisms are found on earth
Study how many species live in a given area and how it changes over time because of human interaction and development.

How do ecologists determine population size and density?
1. Constructing Life Tables- Tracking one cohort (one group) through time. Always drops.
2. The mark-recapture method

How does one estimate population size using the mark-recapture method?
Tagging. Strap something on a fish. Capture them. How many fish are in this stream?

Check on the river with tagged fish a few days alter. Get a fish from the river, but its not tagged. Must be more fish in the stream.

What are dispersion patterns? Name three patterns & give a possible ecological cause for each.
1. Clumped: closely packed. “herd, pack, pod, school” We humans are clumped!

2. Uniform: spacing is predictable. around resources

3. Random: random

What is demography?
-branch of ecology that studies the vital statistics that affect population size. How many die/born?

What are the most important features that influence population growth and decline (assuming
immigration = emigration)?
Birth(B) and Death (D) rates

What is a life table? Mortality rate? Survival rate? Survivorship?
Life table- Tracking one cohort (one group born in a given moment) through time. Number alive drops, average life expectacy

Mortality Rate: measure of # of deaths in a populations
Survival Rate: % of individuals surviving a given circumstance (eg. disease) in a given population for a given period of time
Survivorship: a given group of individuals that live instead of dying

What is a survivorship curve? What kind of mortality rate is associated with each of the three idealized survivorship curves?
Data from a life table can be used to make a survivorship curve. Life history that a species exibits = survivorship curve
Type I- death from old age (human)
Type II- constant (squirrel)
Type III- early death (mussel)

What information is presented in a reproductive table? How can this information be useful?
Concerned with body size and certain age groups!

Useful in a managing a fishery→Reproductive age of females- will the population make more babies.

What is a cohort and how is it used to construct life tables and reproductive tables?
-one group born in a given moment
-a certain age range is used to in life tables and reproductive tables

Why is the age structure of a population important?
Age structure of a population important because you can determine if a species can make more babies. Reproductive age.

What is life history and what are some examples of life history traits?
Certain species have different life histories:
Semelparity and Iteroparity

What are semelparity and iteroparity? In what kind of environment would each be advantageous?
semelparity- live for a time, have one reproductive episode, then die (octopus, spider from Chalotte’s web)
iteroparity- repeated episodes of having babies throughout life

What is exponential population growth? What are r, N, and t? When do natural populations
experience exponential growth? What is zero population growth?
-J-shaped curve
-idealized population living in an unlimited environment
r = difference in per capita birth and death rates.
N= number
T= time

zero population growth (ZPG)→ B=D or dN/dt = B-D, r=0

How is logistic growth different than exponential growth? What is K?
Environment places limit on how many individuals (K) the environment can support.
Logistic growth model has a limit and growth approaches this limit, K. S shaped as opposed to J shaped.
-Carry capacity (K) or equilibrium density

Under what conditions do populations experience logistic growth? Which is more common in natural populations?
Environment places limit on how many individuals (K) the environment can support.
Logistical growth model is a natural realistic representation in nature, but does not capture everything… there are so many other influences (things cannot be controlled by a model)

What are K-selection and r-selection? Which life history traits are advantageous in an
disturbed/variable environment? A stable/predictable environment?
K- selected, stable environments
-be big offspring
-large offspring
-large adults
-competitive
-parental investment
-mortality rate is low
-population number close to/at K
ex. elephants, redwood trees

r – selected, chaotic, stressed or ephemeral environments
-small body
-small offspring
-numerous
-mortality rate variable
-not much investment in offspring
-population size is well below K
ex. weeds, plankton

In what ways does negative feedback between population size and density prevent populations from growing indefinitely?
An increase in density decreases population size because there is a limited amount of resources. Imagine a highly dense area of sea rock. Only so many mussels can survive and live. Limited resources = limited growth

Give an example of a way that understanding factors regulating population growth can be
important for a farmer or a conservation biologist.
See when it is the best time to harvest crabs and when not to because there may not be enough crabs to make babies in the next season.

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