Bio 1B: Ecology Unit

Environmental gradient

gradual change in an environmental variable (like temperature) through space (elevational/latitudinal). Caused by the tilt and roation of the earth which leads to seasons.

Abiotic Factors

Nonliving components of ecosystems (temperature, light, water, soil, pollutants, etc.)

Biotic Factors

Biotic: living things within an ecosystem (plants, microbes, animals)

Species range limits

Disperal, biotic, or abiotic factors can limit species distributions.

Air circulation

Circular patterns of air circulation of moist air rising and drying (releasing rain), dry air rises to 30 degree latitude and absorbs moisture

What is Traditional Ecological Knowledge (TEK) and why is it important to recognize?

Western term to describe understandings of indigenous people, increased interest in learning of TEK as it has been largely excluded from western science

Precipitation

the falling to earth of any form of water (rain or snow or hail or sleet or mist)

Decreases at mid latitudes (around 30 degrees) due to air circulation patterns, highest at equator

More precipitation where annual temperature is hotter

Equinox

Where day and night are at equal length from one another. Sun will be directly overhead at 0 degree equator line.

Solstice

When day and night are at maximum differences from one another.

December Solstice: North Pole is in 24 hour darkness

June Solstice: North Pole in 24 hour light

Identify the levels of hierarchy under Ecology

Organismal < Population < Community < Ecosystem < Landscape < Global

Main Abiotic Factors in Terrestrial Biomes

Temperature and Precipitation

Main Abiotic Factors in Aquatic Biomes

Light and Nutrients

How do temperature and precipitation vary with latitude and altitude?

Hotter annual temperature leads to more overall precipitation.

Rainfaill increases going upward the windward side of a mountain range, as air cools, water vapor condenses and rains. Descending air with reduced moisture results in rain shadow and leward side.

Precipitation is highest at equator and lowest at 30 deg latitude (north and south) due to Hadley cell air circulation

A lot more land in Northern Hemisphere, so more cold land up North than South

Name the three Climatic Zones and describe their temperature and precipitation levels

1. Tropics: 0-25 deg range. warm, wet, weekly seasonal (wet/dry seasons). Highest precipitation

2. Temperate Zone: 25-60 deg, highly seasonal (cold winter hot summer)

3. Polar: 60-90 deg, year round low temperatures, 24h light/dark at solstices

How do seasons differ in areas that are farther from the oceans?

Water warms/cools slowly, causing milder seasons in "maritime" areas by the ocean in contrast to stronger seasonal effects in "continental" areas that are farther from the ocean.

Compare and contrast latitudinal temperature gradients over the past 70M years of Earth's history.

Around 50 MYA, latitudinal temperature gradients were shallow and the tropics extended to 30 degrees

Describe how environmental conditions change along elevational gradients, and how mountains create rain shadows.

Cool air flow goes up mountain and gets cooler, holds less water, precipitates out towards the windward side of the mountain, rain shadow is the region of the mountain with little rainfall because its sheltered from prevailing rain bearing wind by mountain range

Chaparral Biome

Identify area of the globe, environmental conditions, and examples of characteristic biota.

West coast of the United States, the West coast of South America, the Cape Town area of South Africa, the Western tip of Australia, and the coastal areas of the Mediterranean

Precipitation 30-50 cm/year, highly seasonal (winter rain)

Cool Fall, Winter and Spring (10-12 deg C) and hot summer (30-40 degC)

Shrubs, trees, grasses, high diversity and endemism

Browsers (deer, goats), small mammals, amphibians, birds, insects

Fire prone, organisms are fire and drought adapted

Desert Biome

Identify area of the globe, environmental conditions, and examples of characteristic biota.

While most deserts, such as the Sahara of North Africa and the deserts of the southwestern U.S., Mexico, and Australia, occur at low latitudes, another kind of desert, cold deserts, occur in the basin and range area of Utah and Nevada and in parts of western Asia.

Precipitation

Coniferous Forest Biome

Identify area of the globe, environmental conditions, and examples of characteristic biota.

High precipitation: 30-50cm/year, cold winters and warm summers, cone-bearing trees (some fire-dependent), migratory birds, mammals, brown bears, large impact of logging

Tropical Forest Biome

Identify area of the globe, environmental conditions, and examples of characteristic biota.

Around equator

High precipitation

Wet and Dry seasons

Temeperature = high and aseasonal (25-29 degC)

Highest animal and plant diversity

Tundra Biome

Identify area of the globe, environmental conditions, and examples of characteristic biota.

Very north

Precipitation 20-60 cm/y

Cold winters (-30 degC) cool summers (10 degC)

Herbaceous: mosses, grasses, forbs

Dwarf shrubs and trees and lichen, Permafrost restricts plant growth

Migratory birds, large grazers (caribou, musk, oxen, reindeer), predators like foxes, bears, wolves

Significant oil and gas extraction

Predict physiological, morphological, and behavioral adaptations to abiotic conditions characteristics of desert biome

Challenges: lack of water, large temperature fluctuations, sand

Solutions: avoid water loss, improve water gain, modulate heat loss and gain through insulation and physiology

Ex: Camels allow body temp to rise during the day and drop at night to save water (avoid sweating to cool body)

Predict physiological, morphological, and behavioral adaptations to abiotic conditions characteristics of tundra biome

Challenges: cold, snow/ice, lack of food

Solutions: avoid heat loss, camouflage, reduce metabolism, cold tolerance

Mammals: thick, white fur, large feet, waterproof coat, small extremities

Invertebrates: cold tolerant, dormancy, active at low temperatures

Predict physiological, morphological, and behavioral adaptations to abiotic conditions characteristics of chaparral biome

Challenges: lack of water, heat, fire

Solutions: avoid water loss, improve water gain, survive and reproduce after fires

Plants: thick waxy leaves, fire-activated seeds, thermal insulation

Animals: low metabolism, highly concentrated urine, heat loss through extremities

Location of Chaparral Biome

Small sections of most continents.

Coastal areas.

West coast California, West coast of South America, Cape Town of south Africa, coastal areas of the mediterranean

Location of Desert Biome

Sahara of North Africa, deserts of the southwestern US, Mexico, Australia,

Location of Coniferous Forest Biome

Northern Hemisphere, North America, Europe, and Asia (50-60 degN latitudes)

Location of Tropical Forest Biome

Around equator (between 10 degrees north and south)

Around Tropic of Cancer and Tropic of Capircorn

Location of Tundra

The arctic, just below ice caps. Across North America, Europe, Siberia in Asia.

Much of Alaska and Half of Canada

Niche

combination of biotic and abiotic factors that a species needs to reproduce

Life History Traits

Suit of traits related to a species' lifespan and the timing and pattern of reproduction:

Size at birth

Growth pattern

Age and size at maturity

Number, size, and sex ratio of offspring

Age- and size-sepcific mortality and repdrodcution

Length of life

Duration and investment of parental care

Life History Strategies

Life History Strategies are defined by investments into maintenance, growth and reproduction, and trade-offs lead to general patterns of variation along a fast - slow (r to K) axis

r vs. K life history variation

r-selection: selects for life history traits that maximize reproduction and the ability for a population to increase rapidly at low density

K-selection (density dependent selection): selects for life history traits that enhance an individual's fitness when a population is fairly stable

Demography

the statistical study of populations

(we use life tables, age-specific summaries of survival and reproductive rates within a population, by making a "cohort" to inform demography)

Survivorship curve (definition)

A plot of the proportion of numbers in a cohort alive at each age, showing the pattern of survivorship for a population.

Survivorship curve (Type I)

Low death rates during early and middle life, and a sharp increase in death rates later in life.

Found in large animals (humans, elephants, albatross) that produce few offspring but provide them with good care

Survivorship curve (Type II)

Constant death rate throughout life. Straight line.

Found in some rodents, invertebrates, lizards, and annual plants

Survivorship curve (Type III)

High death rates for the young, steeply declines for survivors of early period die-off

Found in organisms with a large number of offspring with little to no care (long-lived plants, many fishes, most marine invertebrates)

Principle of Allocation

Principle of Allocation:

Organisms generally don't live a long time AND reproduce a lot

Individual organisms have limited resources and allocate them towards specific functions and not others

Resources in a life cycle are allocated among growth, survival, and reproduction

Animals allocate time and energy to things like foraging, breeding, caring for offspring, etc.

Plants allocate biomass and nutrients to different parts (roots, stems, leaves, etc.) to carry out different function

Life History Trade Offs

1) current reproduction and survival,

2) current reproduction and future reproduction,

3) number and size of offspring

Y model for allocation trade-offs

Acquisition of resources splits into a Y shape model for 2 branches: 1) investment into survival, 2) Investment into fecundity (producing offspring)

Costs of Reproduction

reproduction in one year limits reproduction another year

less resources allocated towards survival/growth/foraging/etc

Somatic Maintenance

energy spent to maintain body (soma) often equated with allocating resources to survival (in contrast to reproduction)

Semelparous

repoduces only once (short adult lifespan)

Iteroparous

reproduces multiple times throughout life (long adult lifespan)

Describe how species richness changes with latitude, and propose hypotheses for this pattern.

Species abundance and richness is highest at the equator and decreases towards the poles

Hypotheses:

Climatic: primary productivity is higher in tropics, more stable conditions encourages specialization and speciation (narrow niches)

Geographic: greater area supports more species

Historical: longer evolutionary history, no glaciations

Interpret evidence from past climates to illustrate how latitudinal diversity gradients have changed through time.

At high latitudes, there was a diversity decline of inverstebrates upon the transition from hot to cold (cooling earth, Ordovician-Silurian extinction)

BIDE model

A model of population growth that takes into account immigration and emigration, in addition to births and deaths.

Nt+1 = Nt + B + I - D - E

Population size in following time interval = Number of individuals at time t + number of births in the next interval + incoming immigrants - deaths in next interval - emigrants in next interval

Simplified version, assume no immigration/emigration, closed population:

Nt+1= Nt + B - D

per capita

per individual in the population, often just females

r (definition)

intrinsic rate of increase, a percentage change in population size per capita

when r is constant over time, populations grow exponentially

r > 0

population increases in size

r = 0

population does not change in size

r < 0

population decreases in size

Geometric Growth vs. Exponential Growth

Geometric: population growth over discrete time periods

Exponential growth: time intervals are infineitely small and continuous, continuous curve

Population Growth on a Log Scale

Exponential growth will look linear

When does exponential growth occur?

- Populations are introduced into a new environment

- Important predator has been removed

(ex: locust swarm)

Logistic growth

(s-shaped) population growth resulting from density-dependent factors

at low density, growth is exponential, but population growth slows until carrying capacity K is reached

dN/dt = rN*( (K-N) / K)

Density-Independent Factors

Unrealted to population density (cold winters, droughts, storms, natural disasters, etc.)

Density-Dependent Factors

limiting factor that depends on population size. Competition, predation, parasitism, and disease

Apply principles of exponential and logistic population growth to interpret trends in human population growth.

The size of the world population was relatively stable for tens of thousands of years

In the last 12,000 years, we have seen exponential growth

Although our population is increasing, our growth rate is declining which does not fit the assumptions of exponential growth

We add about net 82 million people per year

Population expected to peak around 11 billion in 2100

Demographic Transition

1. High mortality rates and high birth rates

2. Mortality falls but birth rates stay high

3. Mortality stays low and birth rates fall

4. Mortality and birth rates are low

Apply principles of demography to understand the impact of the COVID-19 pandemic on human populations in the US and worldwide

Life expectancy in 2020 was decreased compared to 2019 in 31/36 countries

Populations with a higher proportion of older people have a dramatically higher burden of mortality

Social distancing and other policies to slow transmission should consider the age composition of populations as well as intergenerational interactions

In the US, data shows historically low US population growth rates during the pandemic (R = 431,000), after record low R in 2018-2019 (R = 923,000)

demography/demographic science

the study of statistics such as births, deaths, income, or the incidence of disease, which illustrate the changing structure of human populations.

Comeptitive Interactions

Both species have negative effects on eachother. causing reduced growth, survival, or fecundity (produce offspring)

Exploitative Interactions

Positive effect for one species, negative for the other. Predation, Herbivory, Paratism

Positive Interactions

positive/neutral effects for both. Mutualism, commensalism/facilitation.

Intraspecific competition

Competition between individuals of the same species. This is the mechanism behind density-dependent population growth

Interspecific competition

competition between individuals of different species

Exploitation competition

competition mediated by consumption of shared resource, individuals do not actually physically encounter each other (nocturnal/diurnal rodents/ants competing over the same food)

Interference competition

competition involving direct, physical interaction (lions and hyenas physically fighting for food)

Competitors expend energy to inhibit resource access to the other

Scarcity Principle

no resource is unlimited, therefore resources can become scarce, forcing organisms to divide up these limited resources

Competition arises from scarcity, and is the fundamental process in ecology

Classical perspective of Western economics, ecology, and evolution

Competitive exclusion

Competitive exclusion principle

If 2 species are competing for the same limited resource, the species that uses the resource more efficiently will eventually eliminate the other locally

Only valid if the resource does not vary in time/space, and there is only a single resource

Character Displacement

The tendency for characteristics to diverge more in sympatric (geographically overlapping) compared to allopatric populations to reduce competition

Sympatric species: have overlapping ranges (occur in same place)

Allopatric species: separated by barrier

Exploitative Interactions

One party benefits and the other suffers harm

Predator/prey, herbivore/plant, parasite/host

Asymmetric

Outcomes of exploitative interactions are "asymmetric" (helpful for one partner, harmful to the other)

ectoparasites / endoparasites

ectoparasites: live on the outside of the body

endoparasites: live inside the body

A shifting continuum of symbiosis

Symbiosis is an organism living in or on another organism

These symbiotic relationships include the full sprectrum from paratism to commensalism to mutualism.

Ecological effects of species interactions

species interactions impact ecological processes by determining abundance (carrying capacity), range or distribution, and timing of interacting partners

Positive interactions result in...

Increased abundance, extended range, synchronized activity of partners

Negative interactions result in...

decreased abundance, reduce range, select for altered timing

Coevolution

Reciproval evolutionary changes in two interacting species

Ecological and evolutionary outcomes of competitive interactions?

Competitive exlusion

Character displacement, resulting in niche or resource partitioning

What are the ecological and evolutionaryoutcomes of exploitative interactions?

Boom and bust population cycles

Reducing abundance and range of prey/host, excluding fromotherwise suitable habitat

Defensive and offensive adaptations of morphology, physiologyand behavior

What are the ecological and evolutionaryoutcomes of mutualistic interactions?

Increasing abundance or range of interacting partners•

Adaptations of morphology, physiology and behavior to promoteinteractions•

Increase susceptibility to global change

Counter-adaptation

an adaptation to another organism's adaptation

Realized vs. Fundamental Niche

Realized niche is where an organism lives with the presence of competition and fundamental niche is what it could be without competition (thus much broader)

**think Barnacles example

test: Fundamental and realized niche can be testedby creating three separate sites, 2 will contain one type of barnacleexclusively and the third will contain both. If there is a difference inthe inhabited range then one can make conclusions aboutfundamental vs realized niche.

Name the processes that result in energy flow from the sun to organisms, and carbon cycling through ecosystems.

primary producers capture energy from the sun via photosynthesis

respiration to release stored energy for use in metabolism (releasing carbon to the environment)

energy is transferred up food chains from primary producers to higher trophic levels

Energy flow key concepts

a) Energy for ecosystems ultimately originates from thesun, and energy flows through food webs via trophicinteractions. The degree of connectivity and redundancyof food webs determines their resilience. Both bottom-upand top-down controls regulate ecosystem composition.

b) Biological and geochemical processes cycle nutrientsbetween organic and inorganic parts of ecosystems.

Identify causes and magnitude of inefficiency in energy flow, and the consequences of this inefficiency for the lengths of food chains.

Energy transfer inefficiency:

about 10% of energy is transferred from each level to the next

the rest of the enrgy is lost due to waste and heat production

consequence: limits food chain length (higher productivity ecosystems can have longer food chains)

Keystone species

A species that influences the survival of many other species in an ecosystem. No other species can fill their niche.

Examples: Yellowstone wolves, Pisaster seastars that eat mussels, Elephants, etc.

Ecosystem Engineers

Modify their environment, affecting many other species

Examples: Beavers' dams creates wetland habitats that species rely on

Top-Down control and Bottom-Up Control

Top-Down: abundance of organisms at higher trophic levels controls abundance of organisms at lower levels

Bottom-Up: Nutrient supply or availability of food at lower trophic levels limits the abundance of organisms at higher levels

Trophic cascade

When predators limit the density or behavior of their pray, impacting the abundance of interacting organisms across at least THREE trophic levels

Non-exclusive consumer

Species that can weave into a web at more than one trophic level

aka omnivores

3 types of biodiversity

1) genetic (genetic diversity within a vole population)

2) species diversity (species diversity within a specific ecosystem/biome)

3) community and ecosystem diversity (across an entire landscape of a region)

alpha diversity

mean species diversity at a site/local scale

describes the species diversity within a small community at a small or local scale (one ecosystem)

often measured through # of species in a plot

beta diversity

ratio between regional (y) and local (a) species diversity

species diversity between two separate communities or ecosystems