Ecosystems and living organisms

Evolution

The cumulative genetic changes that occur in a population of organisms over time

proposed by Charles Darwin, a 19th century naturalis

In the wild, any genetically derived traits (such as faster swimming or above-average intelligence) can give one individual survival advantage over others in his/her population.

natural selection

Survival advantage    =      reproductive                            advantage

 If one organism is better survivor, more of their gametes will make it into the next generation in a population.

 Those individuals that are less advantaged may not survive to reproduce or will reproduce less.

strengthens the gene pool of a species by eliminating less advantageous traits through lack (or reduction) of reproductive events in these individuals

Peppered Moths

Natural selection

study in England 1800’s More light than dark moths

Industrial pollution turned trees dark

Population shifted to mostly dark moth

Natural selection based on

four observations about the natural world:

 

High Reproductive Capacity

Heritable Variation

Limits on Population Growth, or a Struggle For Existence

Differential Reproductive Success

Heredity

Transmission of characteristics from parent to offspring

–Instructions from parent to offspring are passed on in the form of genes

Evolution

Changes through time

Darwinism

Changes by natural selection

Neo Darwinism

changes by natural selection through Mendelian inheritance

Modern Synthesis

Combined natural selection with modern understanding of genetics for unified explanation

Includes research in fossils, developmental biology, classification, ecology, biogeography 

Modern Synthesis Explains

with mutations (changes in DNA)

Genetic variability

Mutations can be beneficial, harmful, or of little impact

Chosen for or against

Modern Synthesis Is an attempt

to explain variation among offspring (mutation)

Includes knowledge from genetics, classification, developmental biology, fossils and ecology

Evidence for evolution

Similarities among organisms demonstrate how they are related

Similarities among embryos demonstrate how they are related

Fossil records demonstrate how organisms are related

Adaptations

the structural, functional, and behavioral features that contribute to the success of a species.

Domains of Life

We can trace similarities and make a ‘family tree’ of all organisms

Can change with new knowledge

Many relationships among organisms

Domains of Life Theories

Chloroplasts and mitochondria were separate organisms in mutualistic relationship with cells?

Emerging knowledge about human digestion and gut bacteria

Taxonomy

science of classifying and naming organisms.

Taxonomy Done by

variety of methods:

DNA and protein analysis

Comparing embryology

Fossil record

Comparing anatomy and morphology.

Taxonomy Levels of classification

from the largest (most species inclusive) to the smallest (only one species):

 Domain  Kingdom  Phylum  Class  Order  Family  Genus  Species

Binomial Nomenclature

(Two names)

Population Ecology

Study of populations and why their numbers change over time

Population Ecology Important for

Endangered species

Invasive species

Proper management (ex: deer)

Population

Group of individuals of same species living in the same geographic area at the same time

Population density

the number of individuals of a species per unit area or volume at a given time

Ex: minnows per Liter of pond water

Growth Rate

The rate of change of a population’s size, expressed as percent per year

r = b − d

r = growth rate, b = births/1000 people, d = deaths/1000 people

Change in Population Size

On global scale is due to the number of births and deaths

Growth rate

Can include dispersal in equation

movement of individuals in or out of area

Growth rate dispersal

important for

Population management

Dispersal of genes

Maximum population growth

Biotic Potential = Intrinsic Rate of Growth = Growth rate under ideal conditions

J- Shaped Curve (exponential growth)

Life history characteristics

influence biotic potential:

 Age that reproduction begins

Fraction of the life span during which an individual can reproduce

Number of reproductive periods per lifetime

Number of offspring produces during each period of reproduction

Environmental Resistance Limits

Prevent indefinite reproduction

Food availability, water, shelter, waste/disease, predation, competition, etc.

Carrying Capacity (K)

Maximum # of individuals an environment can support

Causes leveling off of exponential growth

S-shaped curve of logistic population growth

Carrying Capacity of environment (K)

Logistic population growth – S shape

More realistic than exponential

Very useful for management

Rarely stabilizes, bounces up and down

Carrying capacity in nature

is dynamic and changes in response of changes in the environment

Ex seasons

Population Crash

Overshooting carrying capacity can lead to population crash

Abrupt decline in population density

Ex: reindeer dependent on winter forage

Factors That Affect Population Size

Density Dependent Factor

Factor whose effect on population changes as population density changes

Examples:

Predation

Disease

Competition

Sometimes cause Boom-or-Bust Population Cycles

Boom or bust population cycles

oscillations of population level can be difficult to predict or manage

Factors That Affect Population Size

Density Independent Factors

Factors that affects population size, but is not influenced by changes in population density

Examples:

Killing frost

Severe blizzard

Fire

Reproductive Strategies r selected species

Small body size

- Early maturity

- Short life span

- Large broods

- Little or no parental care

- Probability of long term  survival is low

Ex: Mosquitoes and Dandelions

Reproduction strategies k selected species

-Large body size

-Late reproduction

-Long life span

-Small broods

-Slow development

-Low reproductive rate

Ex: Redwood trees and human beings

Survivorship

Proportion of individuals surviving at each age in a population

Formed from life tables

Some populations fit two curves

Herring Gulls

Type III & Type II

Metapopulations

A set of local populations among which individuals are distributed and distinct habitat patches across a landscape

Source habitats

More suitable, births > deaths high emigration (dispersal)

sink habitats

Less suitable habitat, births < deaths Immigration needed to maintain population

Biological Communities

Association of different populations of organisms that live and interact in same place at the same time

Communities vary greatly in size and lacked precise boundaries

Interaction in Oak Forest

Oak Forest Community Relationships

Possible to link Lyme disease to bumper acorn crops

Ecological Niche

An organisms role

The totality of an organisms adaptations, its use of resources, and the lifestyle to which it is fitted

 Takes into account all aspects of an organism’s existence

Physical, chemical, and biological factors needed to survive

Habitat

Abiotic components of the environment

Fundamental niche

Potential idealized ecological niche

Realized niche

= The actual niche the organism occupies

Ex: Green Anole and Brown Anole

Green anole and brown anole

Fundamental niches of 2 lizards initially overlapped

Brown anole eventually out-competed the green anole for resources

Drove out green anole, thereby reducing the green anole’s realized niche

limiting resources

Any environmental resource that, because it is scarce or at unfavorable levels, restricts the ecological niche of an organism

Ex: nutrients, food, territory, water

 Organisms compete when resources are not plentiful

Competition

Interaction among organisms that use the same resource in an ecosystem

Intraspecific

Competition between individuals in a population

Interspecific

Competition between individuals in 2 different species

Species have different K values

When grown together, P. aurelia outcompetes

Competitive Exclusion

One species excludes another from a portion of the same niche as a result of competition for resources

Resource Partitioning

Coexisting species’ niches differ from each other in some way

Symbiosis

An intimate relationship between members of 2 or more species

Participants may be benefited, harmed or unaffected by the relationship

Result of coevolution ( pollination ）

Mutualism

Symbiotic relationship in which both members benefit

Ex: Mycorrhiza = fungi and plant roots

Fungus provide roots with unavailable nitrogen from the soil

Roots provide fungi with energy produced by photosynthesis in the plant

Ex Ant plant

Coral zooxanthellae

Clown fish-anemone

Commensalism

Symbiotic relationship where one species benefits and the other is neither harmed nor helped

 Ex: epiphytes and tropical trees

Epiphytes uses tree as anchor

Epiphyte benefits being closer to sunlight, tree is not affected.

Parasitism

Symbiotic relationship in which one species is be and the other is harmed

rarely kill their hosts

Ectoparasite / Endoparasite

Ex: ticks

Ticks attach themselves to skin of animals and consume their blood

Endoparasite : intestinal worms, filariosis

Ex: Tapeworm

Tapeworm attach themselves into human digestive tube and consume the food intake of the host

Predation

The consumption of one species by another

Many predator-prey interactions

Most common is pursuit and ambush

 Plants and animals have established specific defenses against predation through evolution

Pursuing prey

Chasing prey Dow and catching it

Ex: Day gecko and spider

Ex: Komodo dragon

Ambush

predators catch prey unaware

●Hiding camouflage

●Luring: Attract prey with colors or light

Carnivorous/Insectivorous Plants

Adaptation to nutrient-poor environments

Derive nitrogen from captured insects

Plant Defenses Against Herbivores

Plants cannot flee predators

Adaptations

Spikes, thorns, leathery leaves, thick wax

Protective chemicals that are poisonous or unpalatable

Defensive Adaptation of Animals

Fleeing or running

Mechanical defenses

Ex: quills of porcupines, shell of turtles

Living in groups

Warning coloration

Bright colors that prompt avoidance

Chemical defenses –poisons, venoms

Ex: flamboyant cuttlefish, sea slugs

Camouflage=Cryptic coloration

Animals blend into surroundings

Helps animals hide from predators

Example: pygmy sea horse on gorgonian coral

Keystone Species

A species that exerts a profound influence on a community

More important to the community than what would be expected based on abundance

The dependence of other species on the keystone species is apparent when the keystone species is removed

Protecting keystone species is a goal of conservation biologists

Examples: Yellowstone wolf, beaver

Species Richness

The number of species in a community

Tropical rainforests = high species richness

Isolated island = low species richness

Related to the abundance of potential ecological niches

Richness often greater at margins due to transition - euotone

Ecosystem Services

Important environmental benefits that ecosystems provide, such as:

Clean air to breathe

Clean water to drink

Fertile soil in which to grow crops

Community Stability

Absence of change in makeup of a community

Result of:

Resistance

Resilience

Research has indicated that species richness can make communities more stable

Example: organic farmers and wide array of produce

Gardens as Ecosystems

Gardens can support people and wildlife

Spaces between crops are perfect for r selective species (weeds)

Plant others to outcompete weeds

Crops that support predators of pests; build soil for continual harvest

Rely on mutualisms

Community Development

Succession: the process where a community develops slowly through a series of species

Earlier species alter the environment in some way to make it more habitable by other species

As more species arrive, early species are outcompeted and replaced

Primary succession

Succession that begins in a previously uninhabited environment

No soil is present

Ex: bare rocks, cooled lava fields, etc.

General Succession Pattern

Lichen secrete acids that crumble the rock (soil begins to form)

Lichen     mosses      grasses       shrubs       forests

Bare rock with lichen

Grasses and shrubs

Forest community

Secondary Succession

Succession that begins in an environment following destruction of all or part of the earlier community

Soil is present

Ex: abandoned farmland, open area after a fire, tree fall in a forest

Generally faster than primary succession