Continuity & Change D4.1 —4.3 : Ecology & Environment

Evolution

Change in the heritable characteristics of a population.

Lamarckism

Acquired traits can be passed along (falsified)

Evidence of Evolution

unity & diversity

1. New sequences arise, some become more common

2. Some genes are common to several species

3. Genes in closely relating species are more similar

Artificial Selection / Selective breeding

Domestication of plants & animals

1. Control reproduction, control traits in offspring

2. More desirable traits become more common

Homologous structure

Homo = same

Evidence for evolution:

Same structure, same evolutionary origin

Ex: structural similarities in pentadactyl limb, but different functions

Divergent Evolution

One origin that results in the same structures with different functions

Convergent evolution

More than one origin that results in structures that perform a similar function (same selective pressures), different common ancestors

Ex: bee vs. bird wings

Speciation

Formation of a new species, can produce fertile offspring:

1. reproductive isolation

2. Evolve differently

3. Cannot interbreed

Reproductive isolation

Geographical isolation: physical barriers, different environments

Other factors

Allopatric isolation

Geographic isolation, physical barriers —> separation of species

Speciation in different environments

Sympatric isolation

1. Temporal isolation —> breeding in different seasons

2. Behavioral isolation —> mating rituals, attract different mates

Adaptive radiation

Common ancestor diverges into several different species due to different variations exploiting different ecological niches

Minimizes competition

Ex: Darwin’s finches, variations in beak to adapt to different food sources on the different golopocose islands

Interspecific hybridisation

Breeding between two different species

Sterile offspring (unequal chromosome numbers)

Common with domesticated plants/animals to produce new varieties, Not common in nature because offspring can not reproduce on their own

Reason why courtship behaviors are important to maintain biodiversity —> if not, species would merge back together

Abrupt speciation

Polyploid: more than two sets of homologous chromosomes

1. Results from error in cell division

2. Similar features, but cannot reproduce with diploid organisms

Diversity

1. Ecosystem: Varied environments and species

2. Species: different species

3. Genetic: gene pool within species vary

Biodiversity

Mass extinctions and increasing biodiversity —> increasing biodiversity has to end at some point

Anthropogenic

Caused by humans

1. Overharvesting

2. Habitat destruction

3. Invasive species

4. Pollution

5. Global climate change

Ecosystem

Biotic and abiotic factors in a given area

Interdependency

Ecosystem loss:

1. Lange use change for agriculture

2. Urbanisation

3. Mining

4. Dams

5. Exploitation of resources

Biodiversity crisis

Unprecedented loss of ecosystems, species and genetic diversity

Evidence put together by an intergovernmental (several countries involved) science policy platform on ecosystem services

Evidence:

1. Population sizes

2. Ranges

3. Area

4. Species diversity in an ecosystem

5. Richness and evenness

6. Number of threatened species

7. Genetic diversity within a species

Simpson’s Diversity Index

D: diversity index

N: total number of organisms of all species

n: number of individuals in a particular species

Highest index when you have high:

1. Richness (lots of different species)

2. Evenness (not dominated by one/few species)

Causes of biodiversity crisis

Previous mass extinctions, anthropogenic

Dramatic increase in biodiversity crisis

Conservation of biodiversity

In situ: conservation in the natural habitat (protected areas)

1. No disruption to behavior or evolution

2. Cost effective

3. Active management (invasive species, predators, feeding)

Ex situ: outside the natural habitat (zoos)

1. Captive breeding and release

2. Preservation of endangered species

3. Preservation of eggs/sperm/seeds

Multiple approaches>single approach

EDGE Conservation

Prioritize conservation efforts based on:

EDGE of existence

Evolutionary

Distinct

Globally

Endangered

1. Uniqueness (as opposed to having close relatives)

2. Likelihood of extinction (threat to all populations)

Habitat

Physical conditions or place in which an organism, species or population lives

Abiotic

Non-living components of an ecosystem

Ex: water, sunlight, temperature

More influence in extreme environments

Abiotic Adaptation ex: Adaptations of grasses to sand dunes

Challenges of habitat: low water availability, high salt concentration, sand

Adaptations:

1. Waxy cuticle —> reduce transpiration

2. Stomata in pits —> retains moisture in the air

3. Rolled leaves —> reduce wind exposure

4. Rhizomes —> can extend upward if covered by sand

5. Fructans in roots —> increases osmosis in root tissue

Limiting Factors

Range of tolerance: range of a certain factor that an organism can survive in

Animal distribution:

1. Water availability

2. Temperature

3. Different for different life stages

Plant distribution:

1. Water

2. Temperature

3. Light

4. Soil conditions (pH, mineral content, salinity)

Transect

Line that spawns several different levels of specific variable

Ex: Mountain —> different altitudes determine where species are able to live

Coral Reefs

Coral reefs are ecosystems (many populations + abiotic factors)

Include hard coral and mutualistic algae

Mutualistic relationship requires the algae to photosynthesize

Required conditions:

1. Shallow depth

2. Clarity

3. Alkaline pH

4. Certain salinity

Terrestiral

On land

Biome

Collection of similar ecosystems in different geographical areas

Main factors:

1. Temperature

2. precipitation

Plants and animas in similar biomes have similar adaptations, even though they may not be separated geographically

Convergent evolution

Species that face similar challenges tend to evolve and have similar features (not common ancestry)

Ex: emu and ostrich

Adaptations of Plants ex: Meranti tree

Tropical Rainforest

1. Grows very tall to outcompete others trees for light

2. Dense trunk provides support for tall growth

3. Enzymes for photosynthesis have high temperature tolerance

4. Broad leaves to disperse rainfall

5. Leaves that stay on all year (evergreen) to utilize light/photosynthesis

Adaptations of animals ex: Spider monkey

Tropical Rainforest

1. Long limbs for climbing and swinging through trees

2. Active during the day when it can see best (find food)

3. Tail that acts as a fifth limb (for grasping)

Ecological Niche

The role a species plays in its ecosystem

Role depends on:

1. How it obtains food (specialization reduces competition)

2. Zones of tolerance (range determines habitat)

3. How it interacts with other species in the ecosystem

Obligate aerobes

1. Require oxygen

2. All animals and plants

3. Micrococcus luteus (skin bacteria)

Obligate anaerobes

1. Can only live in anoxic environments

2. Bacteria that causes tetanus

3. Methanogenic archaea

Facultative anaerobes

1. Can live in oxic or anoxic environments

2. E. Coli, yeast

Obligate

No choice

Facultative

Choice

Aerobic

Oxygen

Anaerobic

No oxygen

Photosynthesis

Conversion of solar energy into chemical energy

Groups:

1. Plants

2. Algae

3. Some bacteria

Autotrophs, primary producers

Heterotrophs

Must get source of energy from consuming something else

Holozoic nutrition

Whole pieces of food are eaten and digested internally

Ingestion, digestion, absorption, assimilation, egestion

Mixotrophic

Can gather nutrients/energy in both autotrophic and heterotrophic ways

Obligate mixotroph

Must use both hetero and autotrophic methods

Faculative mixotrophs

Can use one method or the other depending on what is available in the environment

Ex: Euglena

Saprotrophs

Decomposers that digest matter externally

Ex: some fungi and bacteria

Detritivores

Decomposers that digest matter externally

Archaea: 3 ways to get energy (ATP)

1. Heterotrophic (from other organisms)

2. Phototrophic (absorbing light energy)

3. Chemotropic (oxidizing inorganic chemicals)

Denition

Relating to teeth —> relationship between teeth and diet of omnivores and herbivores

Helps to figure out diet of extinct species

Homindae

Family that includes humans, orangutans, chimps, and gorillas

Herbivore

Plant eaters = large flat teeth for grinding

Omnivores

Plant and animal eaters = mixture of teeth including flat grinders and sharp ones for tearing meat

Ex: Herbivorous insects

Insects that eat plants

Mechanisms:

1. Tube-shaped mouthpart that sucks sap out of plant phloem

2. Jawlike mouthparts for biting/chewing leaves

Plant adaptations against herbivores

1. Spines/spikes

2. Stinging parts

3. Toxins

Some herbivores have special adaptations for overcoming theses

Ex: aphids produce saliva that act as a barrier and protects from plant toxin

Predator adaptations

Special adaptations for capturing prey

1. Chemical: venom (cobra)

2. Physical: teeth/claws (lion)

3. Behavioral: ambush (moray eel)

Prey adaptations against predators

Special adaptation for avoiding predators

1. Chemical: toxic (monarch butterfly)

2. Physical: camouflage (stick bug)

3. Behavioral: schooling (snapper fish)

Adaptations of plant form for harvesting light

1. Grow tall so the light is not blocked by other plants

2. Lianas (vines) grow through other trees and use as support

3. Epiphytes (air plants) grow on tree trunks where there is more light

4. Strangler epiphytes climb up trunks, eventually outcompeting the tree for light

5. Shade-tolerant shrubs grow on forest floor where low levels of light are within their range of tolerance

Fundamental niche

The range of tolerance of all of the abiotic factors for a species

Realized niche

The actual niche that a species occupies because part of its range of tolerance is occupied by competitors

Competitive exclusion

One species will outcompete the other if their fundamental niches overlap

Leads to exclusion in parts of the range of tolerance

If a species is outcompeted in all parts of its fundamental niche, it will be excluded from the entire ecosystem —> each organism must have a realized niche to exist in an ecosystem

Ex: climate change

Green house effect

How much heat is captured within the earths atmosphere and heat emitted back into space

Normal vs. enhanced (climate change)

Positive feedback cycles in global warming: Snow / ice

Less snow/ice —> decrease sunlight reflections —> increase radiation absorption —> increase ice melting

Positive feedback cycles in global warming: Heat

More heat —> increase permafrost melting —> increase decay —> increase methane —> increase heat

Positive feedback cycles in global warming: Warm oceans

Warmer oceans —> decrease dissolved CO2 —> increase CO2 in atmosphere —> increase heat —> increase warmth in oceans

Positive feedback cycles in global warming: warm temperatures

Warmer temperatures —> increase drought —> increase fires —> increase carbon release — increase warmth

Carbon sink

Removing carbon dioxide from atmosphere and storing in biome mass

Carbon source

Results of drought, heat and fires in carbon sinks

Ex: burning trees will release a mass of carbon dioxide back into the atmosphere

Net increase of atmospheric carbon

Land-fast ice and sea ice as polar habitat change

Emperor penguins

1. Breeding grounds

2. Distance from sea, not far

3. Early ice breaks can kill chicks

Walruses

1. Use ice for resting

2. Energy expenditure finding ice

Changes in ocean currents

Nutrient upwelling = cool water full of nutrients pushes up against land masses and is pushed toward the surface

Stratification = stabilizes the water in the ocean (stable layers does not encourage mixing)

Warmer surface water decreases ocean currents —> less upwelling of nutrients and altered timing

Effects animals that breed based on the cycle of the currents

Decreases:

1. Nutrient cycle

2. Primary production

3. Energy flow

Poleward and upslope range shifts of temperate species

Species that inhabit mountains

As climate change progresses, the upslope environment gets warmer and become suitable for downslope environment organisms —> leads to competitions

Ex: crested satinbird

Threats to coral reefs

Positive feedback loop = CO2 absorption in water leads to acidification —> decrease in pH —> makes it more difficult for corals to absorb carbon from the water

Calcium carbonate shells of marine organism dissolve

Algae and coral have an interdependent relationship

Coral bleaching = Warm water causes the coral to get rid of (expel) mutualistic algae —> ecosystem collapse

Forest regeneration (reforesting)

Planting trees that have been cut-down

Usually using fast growing species of trees that do not occur naturally

Monoculture

Little/no diversity

Positively affects carbon sequestration in afforestation and forest regeneration but may have negative impacts on other factors that affect ecosystem stability

Peat

Partially decomposed organic matter trapped under acidic, waterlogged soil

1. Essential for anoxic environments

2. Can happen quickly in tropical environments

Events affected by temperature

Plants:

1. Bud bursts (new leaves)

Events affected by photoperiodism

Plants:

1. Bud set (growth stoppage)

2. Flowering (short day vs. long day plants)

Animals:

1. Bird migration

Synchronization of biological events

Very important

Ex: migration and food availability

Photoperiods do not change, temperatures are changing

Interacting species need to synchronize their timing —> one species might be cued by photoperiod (migration) and another by temperature (budding)

Disruption to temperature might throw off timing of events necessary for successful interactions

Disruption to synchrony of events by climate change ex: Caribou & Arctic mouse ear

Caribou eat Arctic mouse ear

Caribou time their spring migration to match peak development of Arctic mouse ear

Mismatch between migration and timing of plant development = not enough food supply

Disruption to synchrony of events by climate change ex: Great tit bird & caterpillars

Great tits eat catepillars

Lots of food supply needed for breeding season —> caterpillar populations peak earlier and starts to decline before tit breeding season —> fewer surviving chicks because no food

Effects of climate change to plants

Invasive species: Warmer temperatures —> increase in pests

Drought and warm temperature: stresses trees and weakens tree

Ex: spruce bark beetle

Together, trees are susceptible to invasive beetles because the tree is weakened with heated stress

Natural selection

1. Overpopulation and competition

2. Variation

3. Survival of the fittest

4. Increase in trait frequency

Evolution as a consequence of climate change ex: Tawny owl

Gene pool

All of the different genes and alleles in a population

Large = lots of diversity

Small = little diversity

Genetic equilibrium

All individuals in a population have an equal chance of contributing to the gene pool (surviving, reproducing, passing along genes)

Natural selection disrupts equilibrium because it gives individuals an advantage making it more likely for them to contribute to the gene pool

Allele frequencies of geographically isolated populations

Different alleles in different frequencies in different locations

Ex: alcohol dehydrogenase alleles & sickle cell alleles

Allele frequencies of geographically isolated populations Ex: sickle cell alleles

High concentration of sickle cell alleles in geographically isolated areas such as Africa

Natural selection pressures = Individuals with sickle cell alleles given an advantage against diseases like malaria because the virus can not attach itself to sickle cells

Neo-Darwinism

Integration of understanding of natural selection and genetics

Evolution

A cumulative change in the heritable characteristics of a population over time

Allele frequency

The proportion of an allele in a gene pool

Evolution & Alleles

A change in allele frequencies in a gene pool

Stabilizing natural selections

Average phenotypes have an advantage over extreme phenotypes

Disruptive natural selection

Extreme phenotypes have an advantage over phenotypes

Directional natural selection

extreme change in phenotype in one direction away from the average (mean) due to environmental changes

Hardy—Weinberg equation to calculate allele / genotype frequencies

Equation used to predict allele frequencies and/or genotype frequencies

p²+ 2pq + q² = 1

p²: frequency of the homozygous dominant genotype

2pq: frequency of the heterozygous genotype

q²: frequency of the homozygous recessive genotype

p + q = 1

p: frequency of the dominant allele

q: frequency of the recessive allele

Assumptions of Hardy—Weinberg equation

Conditions:

1. No mutations (no new alleles)

2. Random mating

3. No immigration/emigration

4. Large population

5. No natural selection

If reality (real life data) is different that predicted values means one of the conditions is not being met —> evolution is happening

Artificial selection by choice of traits

Humans control reproduction in order to get desirable traits (domestication of plants and animals)

Selection results in change of allele frequencies —> selection causes evolution

Stability

1. Constant energy supply

2. Nutrient cycling

3. Genetic variation within a species (survive selective presures)

4. Stable climate