BIO 1B: Ecology

indirect effects

presence of one species may affect a second by way of interactions with a third species

Predict abiotic tolerances of organisms from their geographic distributions

ex:

barnacles:

Chthalamus and Semibalanus

-Semibalanus doesn't live in the upper intertidal-- limited by abiotic tolerances (too harsh)

-Chthalamius doesn't live in the Lower intertidal-- limited by biotic tolerances (competition)

what can limit species distributions?

Dispersal, biotic or abiotic factors

what causes evironmental gradients?

the tilt and rotation of the Earth, which leads to seasons

life history strategies

biological characteristics of a species that influence how quickly a population can potentially increase in number

investments into maintenance, growth and reproduction, and trade-offs

lead to variation along a fast - slow (r to K) axis

Changes in population size reflect:

the sum of births,

deaths,

immigration,

and emigration.

Population growth is constrained by...

density dependence as populations approach the carrying capacity

Communities are structured by interspecific interactions including...

competition,

predation,

parasitism,

commensalism,

mutualism,

and disease

Positive interactions

mutualism and commensalism

increase abundance, extend range, select for synchronized activity of partners (either seasonally or on a daily basis)

negative interactions

competition, predation, parasitism

decrease abundance, reduce range, select for altered timing (seasonally or on a daily basis)

coevolution

Process by which two species evolve in response to changes in each other

ex:

predator counter adaptation:

detect prey by touch/smell

parasites and hosts:

hosts:

-immunity

-toxins

-behavioral (avoidance, self medication)

parasites:

-disrupt immunity

-manipulate host chemistry or behavior

-physical structures to stay in/on

Species richness and composition changes due to...

succession, disturbance, and changes in abiotic conditions

Energy ___ through ecosystem, matter___

flows

cycles

energy flows through food webs via _____

trophic interactions

______ regulate ecosystem composition

Bottom-up and top-down controls

______ cycle nutrients between organic and inorganic parts of ecosystems

Biological and geochemical processes

Environmental gradient

are a gradual change in an environmental variable through space

ex: moving up a mountain slope: more snowy and cold

explanations for latitudinal gradients

increase in species richness or biodiversity that occurs from the poles to the tropics

explanations:

climatic:

-primary productivity greater in tropics (more competition, greater heterogeneity)

-greater stability of conditions, encourages specialization and speciation (narrow niches)

geographical:

greater area= more species

historical

longer evolutionary history (no glaciations)

tropics: seen as a cradle (fast origination rates) and museum (low extinction rates)

Climatic zones

regions of the Earth defined by patterns of temperature and precipitation

Tropics

(0-25): Warm, wet, weakly seasonal (wet/dry seasons)

temperate zone:

(25-~60N): highly seasonal, cold winters and warm/hot summers, large landmasses in northern hemisphere (continental)

Polar

60-90: Year-round low temperatures. 24h dark or light at solstices

abiotic factors

Nonliving components of environment.

biotic factors

living parts of an ecosystem

Species range limits

- species occur where performance is highest along an abiotic environmental gradient

- limited by abiotic and biotic environmental factors

Air circulation

circular:

air rises, drops, precipitation drops out in tropics

low precipitation at 30 degrees (desert)

highest precipitation at the equator (tropics)

Equinox

the time or date (twice each year) at which the sun crosses the equator, when day and night are of equal length

solstice

Either of the two times of the year when the sun is at its greatest distance from the celestial equator

-24 hour sun or 24 hour darkness at poles

ecology is composed of:

-organism

-humans

-biotic and abiotic factors

hierarchical levels of Ecology

1. organismal

2. population

3. community

4. ecosystem

5. landscape

6. global

scientific discipline of Ecology vs traditional ecological knowledge

historical:

-rooted in European ideas of human domination (exploration)

-growing interest in biodiversity for resource extraction

-rise of capitalism and colonialism, production of commodities (exploitation)

modern:

-19th century interest in wilderness and conservation

-weaved with evolution, chemistry, mathematics

TEK

traditional ecological knowledge:

-western term used to summarize the understandings of different indigenous peoples

-originally excluded from Western dialogs, now seen as useful

primary abiotic factors that influence the ecology of organisms in terrestrial biomes

-temperature

-precipitation

primary abiotic factors that influence the ecology of organisms in aquatic biomes

-light

-nutrients

compare latitudinal temperature gradients over the past 70M years:

diversity gradients change after the Ordovician-Silurian Extinction (cooling earth)

shallow gradients in the hothouse world --> diversity declines at high latitudes during icehouse

degree of seasonality (in temperature and precipitation):

temperate and tropical latitudes

equatorial:

decreased temperate seasonality

increased precipitation seasonality (dry and wet seasons)

ex: tropics

polar:

increased temperate seasonality

decreased precipitation seasonality

degree of seasonality (in temperature and precipitation):

northern and southern hemispheres

they are opposite each other

when one half is facing towards the sun, the other is away

degree of seasonality (in temperature and precipitation):

continental and maritime climates.

seasons have stronger effects on climates farther away from the ocean

maritime: lower amplitude of fluctuation

continental: higher amplitude

Sierra willow leaf beetle

live in snowy sierras

have to fit their whole life cycle in a few months when there is no snow

-beetles need snow to survive: it is insulating

-temp is more stable during snowy seasons

-droughts increase cold stress, cause their elevational range to contract

determinants:

upper limits:

-cold temps

-lack of O2

lower limits:

-predation from flies

pressure ___ as elevation ____

temp ___ as elevation _____

decreases

decreases

windward

facing the wind

-rainfall increases going up in elevation on this side

leeward

In the direction away from the wind

-no rain shadow

biome

large, naturally occurring community of organism occupying a major habitat

Atmospheric pressure

the pressure caused by the weight of the atmosphere

decreases as altitude increases

Rain shadow

A region with dry conditions found off the leeward side

it is sheltered by the mountain range from prevailing rain-bearing wings

Primary productivity

rate at which energy from the sun is converted into biomass by photosynthetic producers (plants)

increases w increasing temp and precipitation

Chaparral

-precipitation is pretty low

-highly seasonal precipitation

-cool fall, winter, spring

-hot summer

-shrubs, trees, grasses, herbs, high diversity

-endemism

-browsers (deers, goats), small mammals, amphibians, birds, insects

-fire prone: adapted to fire and drought

endemism

A state in which species are restricted to a single region

desert

-low precipitation

-temp high

-temp variable seasonally and daily

-succulents, cacti, shrubs and herbs

-adaptations to increase heat and desiccation tolerance

Desiccation

drying out

coniferous forest

-medium amt of precipitation

-cold winters, warm summers (highly seasonal temp)

-cone bearing trees (some fire dependent)

-migratory birds, mammals (moose, brown bears, Siberian tigers), bark beetles

-large impact of logging

logging

cutting down trees

tropical forest

-high precipitation

-wet and dry seasons

-temp high and aseasonal

-high animal and plant diversity

Mediterranean climate

a climate marked by warm, dry summers and cool, rainy winters

tundra

-low precipitation

-cold winters, cool summers (not seasonal temp)

-herbaceous (mosses, grasses, forbs, dwarf shrubs and trees, lichen

-permafrost restricts plant growth

-migratory birds, large grazers (caribou, oxen, reindeer)

-predators (foxes, bears, wolves)

-significant oil and gas extraction

Phenotype

1.morphology

2. physiology

3. behavior

-influenced by climate

-phenotype evolves to adapt

Species range

area where a particular species can be found throughout its life

range limits

edge of a species range

desert adaptations

challenges:

lack of water:

-shallow, widespread roots in plants

large temp fluctuations:

-thick and waxy plants

-thick fur

sand:

-closing nostrils

-well camouflaged

-long eyelashes, thick eyebrows

camels:

-allow their body temp to fluctuate during day and night to avoid sweating and water loss

-produce less urine

tundra adaptations

challenges

cold temperatures:

-freeze tolerant invertebrates

-thick, white fur

-small extremities (keep heat in)

snow and ice:

-large feet

-waterproof coat

lack of food:

-enter dormancy

-reduce metabolism

chaparral adaptations

challenges

lack of water:

-thick waxy plants

-concentrated urine

heat

-thick bark in plants

-low metabolism

-heat loss through extremities (big ears)

fire

-fire activated seeds

Niches

the combination of biotic and abiotic resources that a species needs to survive and reproduce

Life history

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

life history traits

size at birth

growth pattern

age and size at maturity

number, size, and sex ratio of offspring

age- and size-specific mortality and reproduction

length of life

duration and investment of parental care

life history stratgies are defined by:

1. investments into maintenance

2. growth and reprod

3. trade offs

lead to patterns of variation

Survivorship curves

plot of the proportion of numbers in a cohort still alive at each age

-shows pattern os survivorship

Type 1 survivorship curve

low death rates during early and middle life and an increase in death rates among older age groups

large animals

-few offspring produced, but with good care

-humans

type 2 survivorship curves

constant death rate throughout life

-rodents, invertebrates, lizards, annual plants

type 3 survivorship curve

high death rates for the young, then a slower death rate for survivors

found in organisms that produce a lot of offspring but dont care for them

-long lived plants

-fish

-most marine invertebrates

Resource allocation

Individual organisms have a limited amount of resources

allocated among growth, survival and reproduction

Animals primarily allocate time and energy

Plants allocate biomass and nutrients

examples of life history trade-offs

current reproduction and survival

current reproduction and future reproduction

number and size of offspring

Y-model

survival vs fecundity

Somatic maintenance

energy spent to maintain the body (soma).

Often equated with allocating resources to survival (in contrast to reproduction)

semelparous reproduction

reproduce only once

octopus, agave

iteroparous selection

multiple times

humans, finch, mosquito

r-selection

selects for life history traits that maximize reproduction and population growth:

reproduce early

short lifespan

short maturation

high mortality rate

many offspring

few reprod per lifetime

no parental care

small ofspring

K-selection

aka density-dependent selection

selects for life history traits that enhance an individual's fitness

-late reprod

-long lifespan

-long maturation

-low mortality

-few offspring

many reprod per lifetime

-extensive parental care

-large offspring

life table

age specific summary of the survival and reproduction rates within a pop

cohort

A group of individuals of the same age.

Demography

statistical study of populations

BIDE model

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

Per capita

per person

R

^N/^t

number of individuals added or subtracted from a population in a given time interval

=B-D

r

intrinsic rate of increase

percentage change in population size per capita (per individual in the population)

N

number of individuals

t

time

geometric growth

population growth over discrete time periods

points on a graph

exponential growth

assumes the time intervals are infinitely small, continuous demography (at any moment in time, some individuals are reproducing or dying).

line connecting dots

logistic growth

Growth pattern in which a population's growth rate slows or stops following a period of exponential growth

carrying capacity (K)

number of organisms that a region can sustainably support

density

Number of individuals per unit area

density dependent factors

factor that limits a population more as population density increases

lift usually becomes more challenging in denser pops, reducing birth rates and increasing death rates:

-fewer resources per individual

-more competition

-more disease

-more predation risk

life expectancy

The average number of years an individual can be expected to live, given current social, economic, and medical conditions.

density independent factors

affect rate of growth of a population at any instant, limited by something unrelated to the population size

-external environmental aspects: cold winters, drought, storms, volcanic eruptions (mainly abiotic factors)

-pops display erratic growth patterns from these events

how do you verify that population growth is exponential?

1. doubling time remains constant

2. linear on a log scale

human population growth is leveling off in many areas-- not exponential anymore

global population growth rate peaked ling ago, and now the rate has been halved-- no longer exponential, but constant

when does population growth stop

number of births= number of deaths

demographic transition

change in a population from high birth and death rates to low birth and death rates

stage 1: high mortality, high birth

stage 2: falling mortality, high birth

stage 3: low mortality, falling birth

stage 4: low mortality, low birth

age structure pyramids

graphical representations of populations' ages

what percent of the population is what age

density is at the bottom-- rapid growth

even distribution (US)--slow growth

density is at the middle/top-- no growth, puts pressure on the younger individuals

impact of the COVID-19 pandemic on human populations in the US and worldwide

-populations with higher proportions of older peoples have a higher burden on mortality (Italy vs Korea)

-social distancing and other policies to slow transmission should consider the age composition of populations as well (mortalities aren't solely dependent on how well countries responded to the pandemic)

-US population ha grown to the slowest rate in recorded history

-births only exceed deaths by R=431,000

density dependent factors lead to _____ population growth curves

logistic

S-shaped

affected by carrying capacity