Biology Exam 1

While life is diverse there is…

Unity

5 characteristics of ALL biological life

1. evolve

2. composed of one or more cells

3. reproduce

4. require information

5. require energy

LUCA

A single-celled prokaryote that all life shares as a common ancestor

Common ancestor

ancestral organism shared by 2 or more descendent linages

Eukaryotic

• single-celled

• multi-cellular

Prokaryotic

single-celled

Example of a prokaryote

Bacteria

Examples of organisms processing information (5 characteristics of life)

• DNA

• Respond to stimuli from environment

• Maintain internal conditions

  • homeostasis

Examples of organisms requiring energy (5 characteristics of life)

• respiration

• photosynthesis

• fermentation

When was Earth formed?

4.5 billion years ago

What life was there on earth at first?

single celled

What did first form of life to do the earth?

created O2 leading to the great oxygenation

What did the Great Oxygenation event do?

earth’s atmosphere changed from CO2 to O2, which allowed for the ozone layer to form

What came after ozone formation?

multicellular life

What is the Cambrian explosion?

when major animal life started to form

When did modern humans appear?

200,000 years ago

How many mass extinctions were there?

5

How do mass extinctions happen?

• When extinctions occur significantly above the background rate

• Global climate or environmental changes are too drastic and/or too fast for organisms to adapt

• Mass extinction is not a total extinction

• Some life survives and adapts to the new environment so it shapes evolution of the next batch of life

Typological thinking - Plato

• until 1700s Plato thought every species was perfect and unchanging

• any variation seen in the population is not important

• everything was created individually, independently by God

• “Plato is Perfect”

Aristotle

• Scale of Nature

• same as typological thinking but he added organization in ascending order from simple to complex

• placed human at the top but below god/angels

• “Aristotle is ascending”

Species

a population of interbreeding individuals in nature able to produce viable and fertile offspring but unable to reproduce with other groups

1800s Lamarck

• gets rid of perfect idea and instead adds species are changing over time

• BUT still kept ladder/scale (change happening linearly)

1850’s Darwin and Wallace (independently)

• evolution by descent with modification

• species change over time

• instead of linear progression, species are related by common ancestry

• species change through natural selection

What does evolution explain?

• how life changes to produce the diversity of life we see today and the evolutionary past

• even with all this diversity there are unifying characteristics of all life (descent with modification)

4 evidence for evolution

1. geological evidence

2. fossil record

3. transitional forms

4. can be observed right now

Fossil Record as evidence for evolution

• through extinction

• concept of extinction didn’t exist until 1800 because of typological thinking

• 99% of all species to have ever existed are extinct

transitional forms as evidence for evolution

• intermediate between ancestral and derived (newer) forms

• NOT ancestors but relatives (through common ancestry)

Observations for right now as an evidence for evolution

• hundreds of populations have been undergoing evolutionary changes

  • bacteria resisting antibiotics

• can be observed on scale of days, weeks, months, depending on species ability to go through generations

evidence for common ancestry

1. Biogeography and Law of Succession

2. Homologies

Biogeography

• Where we live and why

• typological thinking

  • similar environments = same best lineage for that environment

• real life

  • can see distinct lineages in similar environments

  • supports descent with modification

Law of Succession

Always see relationship where living organisms today correspond with fossil records in that environment

Types of homologies

• structural

• developmental

• vestigial

• genetic

• artificial selection

Structural homology

• Similarity in anatomy or morphology from common ancestors

• usually adult organisms

Developmental homology

similarity in embryotic of developmental stages due to common ancestry

Vestigial trait

structure with reduced (or lost) function but similar to functioning structure related species

Genetic homology

similarity in DNA, RNA, Amino acid sequence due to inheritance from common ancestor

Artificial selection

humans allow only those with particular traits to reproduce

phylogeny

• depicts evolutionary relationships

• trees show hypothesized evolutionary relationships

Parts of phylogenetic trees

• tip/leaves

• branch

• node

• root

• time

• hashes

Node in phylogenetic trees

the more recent common ancestor shared by 2 or more linages that split

Root in phylogenetic trees

more recent common ancestor for ALL taxa

Ancestor traits

further back in time and shared by a larger group

derived traits

more recent

monophyletic

• clade

• grouping with a common ancestor and all its descents

non-monophyletic

grouping that lacks a single common ancestor for the group or is missing descendents

Synapomorphies

• a trait found in 2 or more taxa that is inherited from their most recent common ancestor and distinguishes these taxa from others

• shared derived trait (homologous)

divergent evolution

• Process where taxa sharing a common ancestor evolve different traits over time

• trait evolved ONCE in common ancestor

• homologies → divergent evolution

Homoplasy/analogy

• a trait that is shared by 2 or more taxa BUT NOT due to shared ancestry

Convergent evolution

• process where taxa share a trait due to evolving under similar conditions NOT from a common ancestor

• trait evolved multiple, independent times

• homoplasies→convergent evolution

Darwin’s 4 postulates of Natural selection

1. individuals within a population are variable (variability)

2. Variability can be passed on to the offspring (heritability)

3. more offprsing produced than can survive (struggle for existence)

4. Survival and reproduction are not random (fitness)

Biological Fitness

the ability of the individual to produce surviving, fertile offspring relative to others

adaptation

heritable trait that increases the fitness of an individual in a particular environment

ecology

how organisms interact with each other and their physical environment

Abiotic factors

non living, and can produce selective pressures

terrestrial biomes

• combination of climate and vegetation

  • climate is the long-term temperature and precipitation condition found in area

  • vegetation is the dominant growth for physical structure

    • grass, deciduous forest

Marine biomes

• characterized not by climate but by depth, light, water movement

• vegetation is kelp, plankton, sea grass

Ecologial levels of organisms

• individual

• population

• community - collection of species

• ecosystem - biotic and abiotic

• global

Predation

one species kills and eat another (prey)

• +/-

Herbivory

One species eats a plant

• +/-

Parasitism

one species feeds on host, harms it but not instantly kill

• +/-

competition

2 or more species use the same limited resource

• -/-

mutualism

each species benefits from species interaction

• +/+

Keystone Species

• species disproportionally large effect/importance on its ecosystem

• provide important resource or activity to ecosystem

  • pollination, predation, beaver dams being built

• loss of it HARMS ecosystem

Biodiversity

• richness, evenness, and diversity

• increases as you go towards equator

Human effects on biodiversity

1. habitat loss or fragmentation

2. overexploitation

3. invasive species

4. climate change

5. endangered species

Resource partitioning

when 2 or more species use different recourses, times, space to lower competition

Productivity

rate of new biomass formation by any biological group

sampling effect

more diverse communities = higher change of at least one highly productive species

Resource use efficiency

more diverse species = able to use total resource pool more completely and efficiently than if only one species present

Facilitation

certain species assist the growth of other species by providing them with benefits

• mutualism and keystone species

Ecosystem services

all direct and indirect benefits that humans derive from organisms and ecosystem

provisioning services

• provide raw materials

  • food, fuel, medicines, genetic resources

regulating services

• part of earth’s life support system

  • climate moderation, erosion control, water purification

• ABIOTIC

Cultural services

enrich quality of life

• aesthetics, recreation, education, preserves

supporting services

• enable all other ecosystem services

  • pollination

  • pest control

  • nutrient cycling

• BIOTIC

Evolution definition

• heritable change in trait frequency (or allele) in a population of individuals of some species over time

4 mechanisms of evolution

1. natural selection

2. mutation

3. gene flow

4. genetic drift

Natural selection

• process by which individuals with favorable heritable traits for a particular environment survive and reproduce more

• NON RANDOM

• can increase, decrease and maintain genetic variation

Mutation

• random genetic change

• Effect can be neutral, detrimental, or beneficial

• SOURCE OF VARIATION

Genetic Drift

• RANDOM

• decreased genetic variation

• Founder effect and bottleneck effect

Founder effect

occurs when new population is established from a small non-representative subset of the original population

Bottleneck effect

a dramatic reduction in population size caused by a random catastrophe

Gene flow

• movement of individuals leaving one population, joining another, and breeding in it

• INCREASES AND DECREASES genetic variation

• RANDOM

African Origins

• oldest H. sapiens fossils in Africa

• founder effect as evolutionary mechanism as small group migrated each time

  • bc genetic variation decreased outside Africa

Why do some places in the Americas have high genetic variation?

Gene flow from slave trade/colonization

Evidence that we share common ancestor from Africa

• fossil evidence

• genetic homology

why are there unique genetic variations in some places?

• bc gene flow from neanderthals and others

• Natural selection and mutation in different environments

what explains prevalance of rare diseases in populations

Founder effect and LOW gene flow (like the amish) so small population

Endangered species

• population size rapidly reduced

• genetic variation decreases bc genetic drift

• high susceptibility to diseases bc low variation so less chance for beneficial variant existing