Evolution, Biodiversity, and Population ecology

Evolution, Biodiversity, and
Population Ecology
Environmental Science, Spring 2019
Prepared by Kiersten Lippmann, 2019

Hazards of Living in Japan: First
an earthquake, then a tsunami,
then a nuclear meltdown… now
radioactive boars
• http://www.cbsnews.com/news/fukushima
-japan-potentially-radioactive-wild-boars/
• No wonder they have such low birth rate!
• Each boar weighs 200 lbs
• Boars contain high levels of radioactive
element caesium-137, which is 300 times
above the safe limit for consumption
Hmmm…. Another example of where an
adaptable opportunistic species comes in
and just takes over.

So… no eating the boars!
• Boars are aggressive
towards humans
• “It is not really clear now
which is the master of the
town, people or wild boars,”
Tamotsu Baba, mayor of
Namie, told Reuters. “If we
don’t get rid of them and
turn this into a human-led
town, the situation will get
even wilder and
uninhabitable.”

Saving Hawaii’s Native Forest Birds
• Hawaii has many new and
unique species of bird
• Half of Hawaii’s bird species (70
of 140) have gone extinct in
recent times
• Many remain on brink of
extinction

Saving Hawaii’s
Native Forest
Birds cont..
• Hawaii’s forests under siege
starting with Polynesian settlers
• Cut forests
• Introduced non-native pigs, goats,
mongooses, and cattle who ate
non-native plants and the eggs
and young of ground-nesting birds
• Invasive plants introduced and
spread across the altered
landscape

Hawaii’s forest
birds- avian
malaria/pox
• Avian pox and malaria arrived with
introduced mosquitos
• Native fauna not adapted to resist
these pathogens
• Killed off native birds everywhere
except on high mountain slopes,
where it gets too cold for
mosquitoes to survive
• Few native birds exist below
1500m elevation on Hawaii’n
islands

Saving Hawaii’s forest
birds cont..
• Fenced out pigs
• Planted thousands of native plants in
deforested areas
• Restored native forests now growing on
thousands of acres
• Climate change presents new challenges
• As temperatures climb mosquitoes move
upslope, spreading disease
• New strategies needed to preserve flora
and fauna bounty of millions of years of
evolution on the unique Hawaiian Islands.

Evolution: the source of
Earth’s biodiversity
• Species- a population or group of populations whose
members share characteristics and can freely breed
with one another and produce fertile offspring
• Population- a group of individuals of a given species
that live in a particular region at a particular time.
• Evolutions- change in populations of organisms from
generation to generation. Changes in genes often lead
to modifications in appearance or behavior
• Species adapt to their environments and change over
time
• Evolutionary processes influence many aspects of
environmental science including agriculture, pesticide
resistance, medicine, and environmental health

Natural selection shapes
organisms
• Natural selection- inherited characteristics that enhance survival
and reproduction are passed on more frequently to future
generations than characteristics that do not, altering the genetic
makeup of populations through time.
• Natural selection is the primary mechanism of evolution
• Organisms face a constant struggle to survive and reproduce
• Organisms tend to produce more offspring than can survive to
maturity
• Individuals of a species vary in their attributes
Variation is due to differences in genes, environments in which
genes are expressed, and interactions between genes and the
environment

Natural Selection
• Attributes are passed from parent to offspring
through genes
• A parent that produces more offspring will pass
on more genes to the next generation than a
parent who produces few or no offspring
• Next generation, the genes of the better-
adapted individuals will outnumber those of
less well-adapted individuals
• Adaptation- over generations, characteristics,
or traits (Adaptations/adaptive traits), that
lead to better and better reproductive success
in a given environment will evolve in the
population.

Selection acts on
genetic variation
• Genes must code for a trait, for an organism to
pass the trait on to future generations
• Mutations- accidental changes in DNA within
the cell
• If mutation is in sperm or egg cell, it may be
passed on to next generation
• Most mutations have little effect, some are
deadly, some beneficial
• Non-lethal mutations provide genetic variation
on which natural selection acts

Natural Selection cont….
• Sexual reproduction can result in genetic variation
as well through novel gene combinations
• Genetic variation can help populations adapt to
changing environmental conditions
• Example- roughly 10% of little brown bats are
resistant to white nose syndrome
• Environmental conditions determine what
pressure natural selection will exert, which affect
which members of the population will survive and
reproduce.

Natural Selection Cont…
• Divergent evolution- closely related species
that live in different environments tend to
diverge in their traits due to selective
pressures
• Convergent evolution- unrelated species living
in similar environments in separate locations
independently aquire similar traits as they
adapt to selective pressure

Evidence of
selection is all
around us
• First proposed in 1858 by Charles Darwin
and Alfred Russel Wallace, British
Naturalists
• On the Origin of Species
• Birth of modern evolutionary biology
• Explained how organisms traits change
over generations
• Artificial Selection- selection for
domesticated animals that possess traits
we want or like, called selective breeding
• Led to variety of domestic dog breeds
• Crop plants and livestock
• Entire agricultural system is based on
artificial selection

Understanding evolution is
vital for modern society
• Evolutionary processes play a vital role in
today’s society and our lives
• Food we eat (selective breeding)
• Medical advances (understanding infectious
disease- like strains of influenza)

Evolution generates biodiversity
• Just as in crops, pets, and livestock, evolution can elaborate
and diversify traits in wild organisms
• Life’s complexity expressed as biological diversity or
biodiversity
• Includes all levels- species, genes, populations, communities
• 1.8 million species described so far
• Many remain undiscovered or unnamed
• Example- 500 species Hawaiian fruit flies, but identified
about 500 yet formally named and described… there are
probably still more… (for what that’s worth)
• Diversity of species is found everywhere, plants, microbes,
even Antarctic ice harbors microbes
• Soil outside contains high number of species including
insects, mites, millipedes, nematode worms, plant seeds,
fungi, millions of bacteria

Speciation produces new types of organisms
• Earth came to have so many species through
speciation
• Allopatric Speciation is the main way- where
species become physically separated (lava floes,
climate change, timber harvest, sea level rise,
or flying or moving to another area).
• Once separated, populations evolve unique
traits on their own
• Eventually, the two populations can no longer
mate and form two separate species

We can infer the history of life’s diversification
• Innumerable speciation events have
generation complex patterns of diversity
• Histories of divergences are represented in
phylogenetic trees
• The branches illustrate hypotheses to how
divergence took place
• Show relationships among species,
populations, or genes
• Using a phylogenetic tree, we can map traits
onto the tree, and trace when in
evolutionary history those traits appeared
• Also used by taxonomists to identify species

Extinction and # of species
• The fossil record shows the # of species has
increased over time, but just a small fraction
of the species that ever existed are alive
today
• Complexity has evolved, but when conditions
are right, less complex species evolve
• Animals have evolved some incredible
adaptation- photosynthesis, hearts that beat
for a lifetime, eyes, brains…
• Extinction is the disappearance of species
from Earth.
• Species on average spend 1-10 million years
on Earth.
• Number of species in existence is equal to the
number added through speciation minus the
number removed by extinction.

Some species are
especially
vulnerable to
extinction
• Extinction generally occurs when
environmental conditions change
rapidly or drastically enough that a
species cannot adapt genetically to
the change- natural selection is not
give time to work
• Small populations vulnerable
• Endemic species vulnerable
• Endemic species are found in a
particular region and nowhere else
• Island dwelling species vulnerable
• Ex. Only one land mammal- bats-
naturally found in Hawaii so birds
evolved to be ground nesting… taken
out by introduced mammals

Stellar Sea Cow …extinct
• Video- Stellar sea cow

Earth has seen episodes of mass extinctions
• Background extinction rate- one
species at a time
• 5 mass extinction events that killed
off massive #s of species all at once
• Wiped out 50- 95% of species each
time
• 65 million years ago wiped out
dinosaurs- collision of asteroid
• 250 million years ago, 75% to 95%
of all species perished – probably
massive volcanism

The sixth mass extinction is upon us
• We are the cause
• Human population growth and
resource depletion
• Many species extinct, many more
close to extinct
• Loss of species is irreversible
• Biodiversity affects us directly-
organisms provide food, fiber,
medicine, ecosystem services
• Loss of biodiversity threatens our
survival

Ecology and the
Organism
• Ecology- scientific study of the interactions
among organisms and relationships between
organisms and the environment
• Explains and predicts the distribution and
abundance of organisms in nature
• Ecology and evolutions are intertwined

Ecology is studied at several levels
• Levels begin with cells up to
biosphere
• Biosphere- cumulation of all
living things on earth and the
areas they inhabit
• Ecologists- study relationships at
higher levels of the hierarchy
• At organismal level, ecology
describes relationships between
an organism and physical
environment

Population Ecology vs.
Individual Ecology
• Ecology describes the
relationship between an
organism and its physical
environment
• Population ecology examines
the dynamics of population
change and the factors that
affect the distribution and
abundance of members of a
population.

Ecology- key concepts and terms
• Community- an assemblage of interacting
populations that inhabit the same area (ex:
organisms at 2,000 feet in WMNF)
• Community ecology- focuses on patterns of
species diversity and interactions among
species (eg. Predator prey and competition)
• Ecosystems- encompass living biotic
communities and abiotic materials and forces
with which communities interact (air, water,
soil, nutrients)
• Ecosystem ecology- flow of energy and
nutrients in a system by studying living and
non-living components.
• Landscape ecology- driven by widescale
changes like climate change, helps us
understand how and why ecosystems,
communities, population are distributed
across geographic regions.
• Expanding to study of the biosphere as a
whole with new technologies and understanding

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Organismal ecology: habitat
• Habitat = the environment in which an organism
lives
- Includes living and nonliving elements
- Scale-dependent: from square meters to miles
• Habitat use = each organism thrives in certain
habitats, but not in others
• Habitat selection = the process by which organisms
actively select habitats in which to live
- Availability and quality of habitat are crucial to an
organism’s well-being
- Human developments conflict with this process

Organismal ecology: niche
• Niche = an organism’s use of resources and its
functional role in a community
- Habitat use, food selection, role in energy and
nutrient flow
- Interactions with other individuals
• Specialists = species with narrow niches and very
specific requirements
- Extremely good at what they do, but vulnerable to
change
• Generalists = species with broad niches that can use
a wide array of habitats and resources
- Able to live in many different places

Population characteristics
• All populations show
characteristics that help
scientists predict their
future dynamics
• Population size = the
number of individual
organisms present at a
given time
- Numbers can increase,
decrease, cycle or
remain the same

Extinction of Passenger Pigeon
• Video- 100 year anniversary of
extinction of passenger pigeon
• Video- preview of passenger
pigeon documentary, includes
simulation of migration flights of
passenger pigeons

• Population density = the number of individuals within a
population per unit area
- High densities make it easier to find mates, but
increase competition, and vulnerability to predation
- Low densities make it harder to find mates, but
individuals enjoy plentiful resources and space

• Population distribution
(dispersion) = spatial
arrangement of organisms
within an area
- Random – haphazardly
located individuals, with no
pattern
- Uniform – individuals are
evenly spaced due to
territoriality
- Clumped – arranged
according to availability of
resources
- Most common in nature

• Sex ratio = proportion of males to females
- In monogamous species, a 50/50 sex ratio maximizes
population growth
• Age Structure = the relative numbers of organisms of each
age within a population
- Age structure diagrams (pyramids) = show the age
structure of populations

Birth and death rates
• Crude birth/death rates =
rates per 1000 individuals
• Survivorship curves = the
likelihood of death varies
with age
- Type I: More deaths at
older ages
- Type II: Equal number
of deaths at all ages
- Type III: More deaths at
young ages

Four factors of population change
• Natality = births within the population
• Mortality = deaths within the population
• Immigration = arrival of individuals from outside the
population
• Emigration = departure of individuals from the
population
• Growth rate formula =
- (Crude birth rate + immigration rate) - (Crude death
rate + emigration rate) = Growth rate

Exponential population growth
• Steady growth rates cause
exponential population
growth
- Something increases by a
fixed percent
- Graphed as a J-shaped
curve
• Exponential growth cannot be
sustained indefinitely
- It occurs in nature with a
small population and ideal
conditions

Limiting factors restrain growth
• Limiting factors = physical, chemical and
biological characteristics that restrain
population growth
- Water, space, food, predators, and disease
• Environmental resistance = All limiting
factors taken together

Carrying capacity
• Carrying capacity = the
maximum population size
of a species that its
environment can sustain
- An S-shaped logistic
growth curve
- Limiting factors slow
and stop exponential
growth
• Carrying capacity changes
Humans have raised their carrying capacity by decreasing the
carrying capacity for other species

Perfect logistic curves aren’t often found

Lynx- snowshoe hare cycle
• Video- lynx and snowshoe hare

Population density affects limiting factors
• Density-dependent factors = limiting factors whose
influence is affected by population density
- Increased risk of predation and competition for mates
occurs with increased density
• Density-independent factors = limiting factors whose
influence is not affected by population density
- Events such as floods, fires, and landslides

Biotic potential and reproductive strategies
vary
• Biotic potential = the ability of an organism to produce
offspring
• K-selected species = animals with long gestation periods
and few offspring
- Have a low biotic potential
- Stabilize at or near carrying capacity
- Good competitors
• r-selected species = animals which reproduce quickly
- Have a high biotic potential
- Little parental care

K-selected vs. r-selected species

Are humans K or r-selected species?
• Discuss…

Population changes affect communities
• As population in one species declines, other species may
appear
• Human development now displaces other species and
threatens biodiversity
- Generalist species take over
- Niche specific or endemic species die off or are
severely limited

Challenges to protecting biodiversity
• Social and economic factors affect species and
communities
- Nature is viewed as an obstacle to development
- Nature is viewed as only a source of resources
- Human population growth pressures biodiversity

What would
happen if humans
disappeared?
• Video: Earth after humans (6 min)

Preserving biodiversity
• Natural parks and protected areas help preserve
biodiversity
- Often, they are underfunded
- Ecotourism brings jobs and money to developing
areas

Evolution, Biodiversity, and Population ecology

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