Ecology and Evolution Week 1

Ecology

• Study of the interactions of organisms with one another and with their environment

• The study of the distribution and abundance of organisms

Evolution

• change in a populations gene pool over tie

• science of the origins of biological diversity and its distribution

Evolution is NOT

the origins of life

Ecological Systems

biological entities that have their own internal processes and interact with their external surroundings

Individuals

most fundamental unit of ecology

Species

individuals capable of interbreeding and creating viable offspring

exception is bacteria and asexual species

Population

individuals of the same species lining in a particular area and interbreeding

Characteristics of populations

geographic range, abundance, density, change in size, composition

Community

All populations of species living together in a particular area

may cover large or small areas

Ecosystem

One or more communities of living organisms interacting with their nonliving physical and chemical environments

Biosphere

all ecosystems on Earth

First law of thermodynamics

matter and energy cannot be created or destroyed but can change form

Natural selection

a change in the frequency of alleles in a population

Darwins 4 postulates

1. individuals vary in their traits

2. traits are heritable

3. variation in traits causes some individuals to experience higher fitness

Producers (autotrophs)

convert chemical energy into resources ex. photosynthesis

Consumers (heterotrophs)

obtain their energy from other organisms

Mixotrophs

can switch between being producers and consumers

Scavengers

consume dead animals

Detritivores

break down dead organic matter into smaller particles

Decomposers

break down detritus into simpler elements that can be recycled

Predation

an organism kills and consumes an individual

parasitism

one organism lives in or on another organism

herbivory

one organism consumes producers

Competition

two organisms depend on the same resource have a negative effect on one another

Mutualism

two species benefit from each other

commensalism

secies where one is benefitted and the other is unaffected

Habitat

physical location where an organism lives; absolute distinctions rarely exist

Niche

range of abiotic and biotic conditions an organism can tolerate

• no two species have the same niche

Scientific method

1. hypothesis

2. predictions

3. test: manipulative experiment, natural experiments, mathematical models

hypotheses

idea that could explain a repeated observation

manipulative experiments

hypothesis is tested by altering a factor hypothesized to be the cause of a phenomenon

treatment

factor that we want to manipulate in a study

control

included all aspects of an experiment except the factor of interest

natural experiment

an approach to hypothesis testing that relies on natural variation in the environment to test a hypothesis

mathematical models

set of equations that correspond to hypothesized relationships among
the system’s components.

• often test mathematic models using natural or
  manipulative experiments.

Greenhouse gases

compounds in the atmosphere that absorb infrared heat energy emitted by Earth and then emit some of the energy back toward Earth.

• High amounts of these gases can increase average Earth temperatures

Bivoltine Life cycle

Two life cycles

population approach

examines variation in number, density, and composition of individuals over time and space

population dynamics

influenced by interactions with other species

fundamental unit of evolution

population

population

a group of individuals of the same species that live in the same area

spatial structure

pattern of density and spacing of individuals in a population

fundamental niche

range of abiotic conditions under which a species can persist

what can prevent a population from persisting in an area

competitors, predators, and pathogens

realized niche

range of abiotic and biotic conditions under which a species does persist

geographic range

a measure of the total area covered by a population

Lewis and scarlet monkey flower demonstrated what

plants are limited by unsuitable environmental conditions

Fremont’s leather flower

plants are restricted by variation in glade soil structure and quality, an example of small scale variation

temperature change can cause

a shift in the geographic range of species

Endemic

species that live in a single location

cosmopolitan

species with very large geographic ranges that can span several continents

abundance

total number of individuals in a population that exist within a defined area

provides a measure of whether the population is near extinction or thriving

population density

the number of individuals per unit area or volume, calculated by dividing abundance by area

if population density is greater than what the habitat can support

some individuals have to leave or the population experiences lower growth and survival

population dispersion

spacing of individuals with respect to one another within the geographic range of a population

clustered dispersion

when individuals are aggregated in discrete groups

evenly spaced dispersion

when each individual maintains a uniform distance between itself and its neighbors

random dispersion

when the position of each individual is independent of other individuals

population dispersal

movement of individuals from one area to another

Survey

uses subset of a population

area and volume based survey

defines the boundaries of an area or value and individuals within are counted

line-transect surveys

surveys that count the number of individuals observed as one moves along a line

population characteristics (5)

geographic range, abundance, density, dispersion, and dispersal

mark-recapture survey

mark a subset of population, return it, capture second sample after time has passed

lifetime dispersal distance

average distance an individual moves from where it was born to where it reproduces

reducing the range of a population will ______ the size of the population

reduce

the density of a population is ______ correlated to the body size of the species

negatively

dispersal limitation

absence of a population from suitable habitat because of barriers to dispersal

habitat corridor

a strip of favorable habitat located between two large patches of habitat that facilitates dispersal

ideal free distribution

individuals distribute in different habitats to have the same per capita benefit

• resource depletion lowers the fitness

subpopulation

large population is broken up into smaller groups that live in isolated patches

basic meta population model

a model that describes a scenario in which there are patches of suitable habitat embedded within a matrix of unsuitable habitat; all suitable patches are assumed to be of equal quality

spatial structure models

metapopulation, source-sink, landscape

metapopulation

set of local populations linked by dispersal

each subpopulation has its own independent

birth and death rates

patches

suitable habitat

matrix

barrier to dispersal

source-sink model

recognizes difference in quality of suitable habitat patches

landscape model

considers effects of differences in the habitat matrix

the study of the structure and growth of populations

demography

November 2022, October 2011 amount of people in the world

8 billion, 7 billion

what basic processes have direct effects on population size?

birth and immigration, death and emigration

two models of population growth

geometric growth and exponential growth

model with discrete time intervals of population growth

geometric growth

model with continuous time / overlapping generations with year round reproduction

has a smooth curve of population increase as a function of time

exponential growth

factors that limit population size regardless of the populations density

common factors include climatic events : tornadoes, floods, droughts

density independent

factors that affect population size in relation to populations density

density dependent

rate of population growth decreases as population density increases

common factors are limiting resources like food and nesting sites

negative density dependence

geographical relationship that shows how decreases in population density over time lead to increases in the size of each individual in the population ( slope of -3/2)

self-thinning curve

rate of population growth increases as population density increases

aka inverse density dependence or Allee effect

positive density dependence

maximum number of individuals an environment can sustain indefinitely

density dependent (logistic) population growth

represented as K in logistic growth model equation

carrying capacity

growth model that describes slowing growth of populations at high densities

logistic growth model

shape of the curve when a population is graphed over time using the logistic growth model

s-shaped curve

point on a sigmoidal growth curve at which the population has its highest growth rate

inflection point

proportion of individuals that occur in different age classes in a population

age structure

age structure pyramid with broad base/ narrow base / straight

growing / declining / stable

summarize ages of life, death, and reproduction

only looks at females (hard to tell who fathers)

contains class-specific survival and fecundity data

life tables

x in a life table represents

age class

nx in life table

number of individuals in each age class immediately after the population has produced offspring

sx in life table

survival rate from one age class to the next age class