Life: Notes

Science and Scientific Methodologies



Learning objectives:

1)  Explain what science is and its role in human thought 

2) Describe and explain the three different ways of scientific reasoning: Deduction, Induction, and Abduction

3) Distinguish and apply those modes of reasoning in a scientific investigation

4) Recognize valid scientific questions in different areas of knowledge 




Goal of science

  • Establishment of general laws/ theories

  • Adequate description of things and events

  • Events may be explained and understood

  • Describe our world and understand the causes of what we observe in the world 



Types of questions

  • What?

    • Description/ identity 

    • What is this thing?

  • Why?

    • Cause/ explanation

    • Why did this happen?

  • How?

    • Function/ quantity 

    • How does this thing work?

  • If you want to know something, you need to know what to ask. 

  • Fact

    • An observation that has been repeatedly confirmed.

  • Hypothesis 

    • A tentative statement about the natural world leading to deductions that can be tested.

  • Theory

    • A well established explanation of the natural world that is based on tested hypotheses. 

  • Law

    • Statements based on repeated experiments or observations that describe a range of natural phenomena. 



The scientific method/ process



Observation/ question -> Research topic area -> Hypothesis -> Test with experiment -> Analyze data -> Report conclusions-> repeat.

  • There is no ONE scientific method, but there ARE different scientific methodologies. 

    • Deductive 

    • Non- deductive

      • Inductive 

      • Abductive 

  • Deductive

    • Consider a set of premises or hypotheses

    • Draw a logical conclusion from those

      • Example: “All insects have 6 legs.” -> “The grasshopper is an insect” -> The grasshopper has 6 legs. 

    • BUT… The method is unable to verify those premises. (It is assumed to be true.) Falsehoods can be concluded, even if they are logical. 

      • Example: “All snakes are venomous” -> “Black widows are venomous” -> Black widows are snakes. 

  • Inductive

    • Aim for broad generalizations based on specific observations

    • Use the available data to draw the best conclusion possible from the data 

    • Aristotle said that knowledge building is primordially a SENSORY EXPERIENCE. 

    • General laws are inferred from particular facts, a guess or tentative explanation

  • Problems with inductivism 

    • Just because something happens often doesn’t mean it's guaranteed to continue to happen.

      • “Past does not predict future”

    • Biases on data collection

      • “Just because you never see a black swan, doesn’t mean it doesn’t exist”



Hypothetico- deductive method

  • A hypothesis is formed by the first two steps of inductive reasoning

  • Hypothesis is tested by validating or falsifying a prediction 

  • If the hypothesis is true, the deduction must be too.

  • Deduction is tested with experiments/ observations 

  • If deduction is false, the hypothesis is falsified. 



Abductive method

  • Based on limited or incomplete explanation.

  • Looks for the most likely explanation, to the data, given previous knowledge. 



We use abduction to produce theories and hypotheses. 

We use deduction to predict potential test evidence. 

We use induction in the act of testing those hypotheses. 

Only statements from which a testable prediction can be made into a scientific process. 



Error and biases



Learning objectives:
1) Identify and explain the nature and sources of error in experiments  

2) Distinguish between Accuracy and Precision and the implications of those qualities in science

3) Develop basic proficiency in the usage of spreadsheets to do basic statistical calculations 

4) Explain what biases are and how they can mislead your thinking on a scientific pursuit




Science and uncertainty 

  • Uncertain -> it can change, like any human activity.

  • Science can be something we don’t know.

  • Scientists are aware of those uncertainties & try to control them.

  • Without acknowledging those, scientific results are meaningless.

Measurements

  • Property of something 

    • How heavy, tall, hot, long, etc.

  • Using an instrument

    • Ruler, weighing scales, stopwatches, etc.

  • Uncertainty: “Give or take” -> difficult to be exact. 

  • Example: 37.58 (magnitude/ value) + / - 0.01 (uncertainty/ error) cm (unity)



What is error?

  • A basic assumption in any scientific endeavor that no measure is correct. 

  • Error is the differences between observed/ measured values.

  • Error ≠ uncertainty

  • Accuracy

    • Trueness of an answer/ measure

    • How correct or close to the true answer or measure is. 

  • Precision

    • Refers to the spread of the values

    • How close to each other your measures/ answers are. 

  • We can guarantee precision, not accuracy. 

  • Why precision? 

    • Repeatability and falsifiability 

  • No scientific hypotheses/ experiment can guarantee absolute accuracy (truth) of its content, but all of them have to guarantee precision. 



Two main kinds of scientific errors

  • Random (or indetermined)

    • Causes: Observers’s judgment, unpredictable fluctuations

    • Effects: Affects precision- how close answers are to each other. 

    • Mitigation: Cannot be minimized, but it can be changed in experimentation. 

  • Systemic (determined)

    • Causes: Consistent and repeatable causes that shift all measurements in the same directions. 

    • Effects: Affects accuracy- how close to the truth. 

    • Mitigation: The whole experiment must be restarted and measurements discarded. 



Mathematics and errors

  • Standard deviation 

    • Formula


    • No two measurements will be the same, especially in biology. 

    • There can be outliers. 

    • Outliers can impact averages and calculations that lead to false conclusions. It’s important to correct for outliers. 

    • Statistical treatment that allows access to the spread of your data. 

    • Is the variation of data random or is the differences of the data significant? 

  • Standard error

    • Formula:


    • Standard deviation of a particular distribution and estimates how close the sample mean is to the true mean.

    • It allows us to compare different sets of data collected from the same sample. 

  • Mean 

    • Average (data range)

  • Standard deviation

    • STDEV (data range)

  • Standard Error

    • STDEV (data range)/SQRT (count(data range))



Biases

  • Definition: A systematic distortion that causes error in different ways.

  • Can and most likely will falsify your data. 

  • Can get to the right answer for the wrong reasons. 

Biases come from…

  • Context

  • Personal beliefs

  • Preconceptions

  • Skewed information sources

Problems with biases…

  • We don’t realize we are biased. 

  • Some are shared by such a big group of people which makes it harder to get rid of them. 



Science is made by humans so it is imperfect!



What is life?



Learning objectives:
1)  Explain why "life" is a difficult concept to determine 

2) Describe and explain the characteristics of life as used in Science

3) Distinguish between living and nonliving things according to science

4) Defend a position on a two-sided matter using reputable sources and evidence-based arguments




Biology = The science of life.

  • Life is a process, not a substance. 

    • Theological

    • Philosophical 

    • Legal

    • Scientific 

  • Scientific definitions describe life, rather than define it. 



7 characteristics of living things 

  1. Order/ organization

    1. All lifeforms are ordered & structured into small unities. 

  2. Reproduction/ replication

    1. All lifeforms can produce new organisms (heredity)

  3. Growth/ development

    1. All lifeforms increase in size in all their organizational units (develop/ mature)

  4. Sensitivity

    1. All lifeforms can perceive intrinsically (its own conditions) and extrinsically (the environment that surrounds it). 

  5. Energy process

    1. All lifeforms can acquire and use energy to fuel their multiple processes. 

  6. Regulation

    1. All lifeforms can regulate their internal environment to a constant state (homeostasis)

    2. Metabolism, anabolism, catabolism

  7. Adaptation/ evolution

    1. All lifeforms are capable of change over time to better survive in its environment. 


The Species Problem



Learning objectives:

1) Explain the "species problem" and its effects on biodiversity understanding

2) Describe the different species concepts

3) Analyze and evaluate different species concepts, pointing out their strengths and weaknesses

4) Define the Hardy-Weinberg principle and discuss its importance (Readings)

5) Explain the four main processes that lead to Evolution: Gene drift; Gene Flow/ migration; Mutations; and Natural Selection (Readings)





Species

  • From latin = appearance, quality 



Some usages

  • Type/ kind

  • Image/ appearance

  • Coin or coined silver or other metal, currency

In biology…

  • Hard to define (the species problem)



Biological species concept 

  • A species is a group of actually or potentially interbreeding natural populations, which are unable to successfully mate or reproduce with other such groups. 



Problems with that concept

  • Interbreeding 

  • Not always straightforward (fossils) or possible t o observe (dinosaurs)

  • Asexual reproducing beings

  • Hybridization (Hybrid = offspring of crosses between different species)

  • Ring species

    • A chain of animal groups that live in a circle, where each group can have babies with its closest neighbors, but the two groups at the very ends of the chain are too different to breed together.

Scientists want

  • Universiability

    • Apply to as many types of organisms as possible

  • Applicability 

    • Applicable in all circumstances

  • Theoretically significant 

    • Describe real events to further understanding 



Morphological species concept:

  • A species is a set of individuals with morphological features in common. (Similarity)

Problems

  • Subjective

  • Outliers

  • Sibling species 

    • Closely related species with no gene exchange but nearly indistinguishable

  • Intraspecific variation 

    • Species vary so much that they should be considered a different species, but they live in the same area & interbreed. 

  • Sexual dimorphism 

    • Males/ females or juveniles/ adults look very different, but they are members of the same species. However, they are sometimes identified as different species. 

Ecological species concept

  • A species is a set of organisms adapted to a particular set of resources- called a niche in the environment. 

Problems

  • “Niche” is hard to define objectively 

  • If two or more organisms' niches intersect, are they the same species?

Genetic species concept

  • A species is a set of individuals that share 98% or more of similarity in a particular gene. 

Problems

  • “Random” percentage for similarity 

Phylogenetic species concept

  • A species is the smallest group of organisms that has at least one diagnostic character. 

Problems

  • Are differences relevant?

Philosophical questions

  • Does biodiversity really fall into discrete units we can call a species?

  • Or are species a man-made artificial category?

Natural kinds

  • Natural

    • Natural grouping, not artificial, specific properties that distinguish from other groups. 

Species Problem

  • Are species a natural kind? Or are they just abstract constructs of human rationale?

  • Single sort of species or many sorts?




Studying life: Systematics



Learning objectives:

1) Distinguish between the main branches of systematics: phylogenetics and taxonomy

2) Describe and explain the main elements of a phylogenetic tree and how to extract information from it

3) Explain the LUCA concept and the evidence that supports it.

4) Differentiate between monophyletic, paraphyletic, and polyphyletic groups; homology and analogy; convergence and divergence

5) Explain the Linnaean classification system, connect it to the modern understanding of evolution, discuss its importance, and be able to criticize grouping as being modern or not. 

6) Explain how systematics are scientific endeavors and how repeatability and falsifiability are possible on phylogenies and taxonomic hypotheses. 




Systematics= The field of biology that comparatively studies features of organisms and the relationship among themselves and conveys this information in a meaningful way. 



Goals

  • Phylogenetics

    • To reconstruct the pattern of ancestor to descendant species through time. 

  • Taxonomy

    • To name and describe life



Natural selection= non-random

Gene drift= random

Gene flow/ migration= random

Mutations= random



Uncovering evolution steps: Phylogenetics

  • Phylogeny

    • A depiction of ancestor- descendant relationships between 2 or more organisms. Usually shown in a tree. 

  • LUCA

    • “Last Universal Common Ancestor”

    • Single-cell free-living organism 

    • Metabolize hydrogen 

    • Extremophile (acid/ hot)

Evidence for LUCA

  • All living organisms we know…

    • Use RNA & DNA as genetic material

    • Use the same 20 L-amino acids to build up proteins and D-sugars to process energy 

    • Have ribosomes

    • Have a lipid bilayer cell membrane 

    • ATP synthase

  • A phylogenetic tree = the hypothesis of relationships among different taxa 

    • Observable data

    • Can be falsified 

Evidence used to construct phylogenetic hypothesis

  • Characters

    • Observable properties or attributes of a given organism

    • Can be divided into character states 

      • Observable variations of those attributes

Data we can use

  • Sources of characters:

    • Anatomy

    • Fossil record

    • Behaviors that have a genetic basis

    • Ontogeny and development

    • Molecular information

Different reasons for look alike

  • Homology

    • Similarity due to common ancestry, divergent evolution 

  • Analogy

    • Similarity due to similar selective pressures, convergent evolution

How do we tell them apart?

  • Morphological similarity

    • Resemblance in detail

  • Topological similarity

    • Similar preposition in relation to neighboring structures or organs

  • Ontogenetic similarity

    • Similarity in embryological development

  • Congruence

    • Agreement with the rest of characters story



Monophyletic group

  • A group of taxa that encompasses all the derivatives from the same node.

Paraphyletic taxa

  • A group of taxa that encompasses only some of the derivatives of the same node.  

Polyphyletic taxa

  • A group of taxa that encompasses derivatives from multiple nodes. 



Taxonomy: Naming and describing life

  • Binomial Nomenclature 

    • A system of two part names: Genus and species name 

    • Species name: italized 

  • Hierarchical Classification

    • System is organized in a series of categories

    • Mutually exclusive and subordinate 

  • Modern Classification

    • Natural groups

    • Reflect natural or monophyletic groups 


The Origins of Life



Learning objectives:

1) Describe the elements of life and where and how they were present on Early Earth

2) Explain what abiogenesis means in scientific terms and differentiate it from non-scientific uses

3) Explain the different hypotheses for the origin of life, their strengths, and their gaps

4) Explain the importance of the Miller-Urey experiment.

4) Follow the chronological steps and explain the challenges of life from inorganic compounds to the first protocells. 



Geologic Time Scale 

  • Divided into 4 eons. 

  • Both eons are divided into eras. 

  • Eras are divided into periods. 

  • Periods are divided into epochs. 

  • Ga (Giga annum) = 1 billion years Ma (Mega annum) = 1 million years Ka (Kilo annum) = 1 thousand years



The SuperEon Precambrian

  • Makes up for about 7/8ths of the Earth’s history: From the formation of the planet

  • Key events

    • Origin of life

    • The origin of eukaryotic cells

    • The appearance of multicellular organisms

Early Earth’s environment

  • Temp was VERY hot

  • Volcanic activity

  • Asteroid bombardment 

Late Heavy Bombardment

  • Marked by a constant bombardment of meteors. 

  • Moon formation -> impact of a theia (a Mars sized planetoid)

  • Effects

    • Changed the temp of the planet

    • Changed composition of atmosphere

    • Delivered rare but necessary life elements 

      • Example: Phosphates

    • High energy released could have also delayed the origin of life



Archean (4.2-5 billion years ago)

  • Marked by a severe diminishing of the bombardment and the first emergence of life

  • Stromatolite

    • Sedimentary formations created (3.4 billion years ago)

  • CHNOPs- the elements of life

    • Carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur



Abiogenesis (1920s)

  • Life originated from non-living compounds 

  • Consists of: Proteins, lipids, nucleic acids, carbohydrates

  • The atmosphere consisted of…

    • Water

    • Carbon dioxide 

    • Nitrogen gas

    • Hydrogen

    • Methane 

    • Hydrogen sulfide



Hypotheses of Origins of Life

  • Primordial Soup

    • Chemically reducing atmosphere 

    • Produce the first organic monomers

    • Accumulated to make a “soup” to create more complex compounds. 

  • Problems

    • Fewer of the reducing molecules

    • Way more CO2, very little CH4

  • Hydrothermal vents

    • Cracks in the ocean crust create a gradient in positively charged protons that serve as a “battery” to fuel creation of organic molecules and proto-cells. 

  • Panspermia

    • Life is widespread throughout the universe and can colonize different planets. 

  • Problems

    • Doesn’t answer question

    • Hard to test

  • Molecular panspermia

    • Small organic molecules used in the early stages of life might have originated extra-terrestrically 

    • Supported by real evidence 

  • Metabolism First

    • Small chemical reactions would occur in early Earth

    • Release free energy that would power more complex molecules 

  • Replication First

    • RNA came before DNA

    • RNA can replicate itself & catalyze reactions



Cell Membranes

  • Lipid bilayer -> forms sphere around cell contents




The History of Life

  • LUCA came to be 3.5-3.8 BA



Rise of Early Prokaryotes

  • First single-cell organism 

  • DNA loose in the cytoplasm as a circular loop

  • Outer cell membrane surrounds cell wall

Cyanobacteria and photosynthesis

  • Pigments

    • Ability to use sunlight instead of thermal vents as a source of energy (phototrophy)



Proterozoic( 2.5 BA- 538 MA)

Great oxidation event (2.3-2.7 BA)

  • O2 began accumulating in the atmosphere and rusting iron rich rocks. 

  • Eliminated many lifeforms

Consequences

  • Allowed for oxidation and oxidative processes, blocking UV light

  • Solved energy process- independence of inorganic forms of energy

  • Changed composition of atmosphere, diminishing CH$, increasing CO2 and H2O

  • Reduced GHG effect



Rise of Eukaryotes (1.65-2.2 BA)

  • Larger and more complex than prokaryotes

  • Nucleus that holds genetic material, wrapped in chromosomes 

  • Membrane bound organelles

  • Endosymbiosis

    • The idea that some eukaryotic cell organelles were once free living organisms. 



Unicellular vs. Multicellular

  • Unicellular

    • All life functions carried out within a single cell

  • Multicellular

    • All lifeforms function with many cells.

Advantages:

  • Division of labor

  • Larger body size

  • Store more nutrients



Ediacaran Biota (541-635 BA)

  • Unique body composition

  • Lacked mouthparts 

  • Soft-bodied organisms preserved worldwide as fossil impressions in sandstone


The History of Life



Learning objectives:

1) Describe the characteristics of prokaryotic and eukaryotic cells, differentiate between them, and explain the evolutionary significance of those characteristics 

2) Differentiate between the two major Endosymbiotic theories (Symbiogenesis and Inside-Out hypotheses), their strengths, and gaps.

3) Identify the major steps in the evolution of life on Earth;  organize them in chronological order and demonstrate how each step depended on the previous.

4) Summarize the major extinction events, identify commonalities amongst them, and correlate them to our present situation



The Last Eon: The Phanerozoic 

Periods:

  • Paleozoic 

    • 251-541 MA -> Cambrian (485-541 MA)

  • Mesozoic 

    • 66-251 MA

  • Cenozoic

    • 66 MA - present



Cambrian Era

  • Rise of bones (unique to vertebrates)



Ordovician (443.8-485.4 MA)

  • Increased marine fauna by x4

  • Skull and backbone development which helps with protection + locomotion



Colonization of land (470 MA)

  • Life began to move to land

  • Life was restricted to water before this

  • Lichen was one of the first on land organisms as well as algae



1st mass extinction- Late Ordovician (444-447 MA)

  • Killed 85% of species

  • Due to global warming, volcanism, anoxia (lack of oxygen)



Silurian (419.2-443.8 MA)

  • First land animal

    • A millipede

  • First vascular plants

    • Cooksonia + agalopython

  • 2 major groups of arthropods and mandibulates originated in ocean

    • Arthropods: Scorpions, spiders, etc. 

    • Mandibulates: Insects, myriapods, etc. 

  • Appearance of jaws 

    • More diverse diet

    • Can eat things larger than your mouth

    • Use of teeth to close the mouth



Devonian (359-419 MA)

  •  Increases weathering & erosion of rocks (Soil)

  • Allows the rise of forests (358-385 MA) 

  • More photosynthesis -> more oxygen

  • GHG decreases, temp decreases

  • Increase in CO2 consumption

  • Major plant groups evolved except flowering plants

  • AGE OF FISHES -> enormous increase in biodiversity of fish

  • Vertebrates move to land "walking fins"

    • Foot like structure develops



2nd Mass Extinction (Late Devonian 360-375 MA)

  • Killed 70% of all species

  • Cause: ocean acidification, volcanism, acid rain



Carboniferous (209-359 MA)

  •  Climate wet & warm

  • Extensive swamps + rainforests spread around more O2 in atmosphere

  •  Coal reserves formed from remains of those forests

  • Higher O2 -> creatures could be bigger

  • Amphibians are dominant vertebrate lifeforms 

    • Age of the Amphibians



Permian (251-298 MA)



  • Formation of some modern mountain ranges

  •  Sea levels dropped to the lowest point in history.

  • Temps dropped a lot in temperature 

  • Diversification of 2 of 3 main groups of land vertebrates:

  • Synapsids 

    • Mammal ancestors 

  •  Diapsids 

    • Dinosaur ancestors



3rd Mass Extinction "The Great Dying"

  • 70% of all land organisms



  • 90-95% of all marine species became extinct in 200,000 years.

  • Causes: 

    • Release of CO2, sulfur dioxide, hydrogen sulfide

    • Results in global warming, aridity, and ocean acidification

    • Massive wildfires, deforestation, and soil erosion. 



The Mesozoic (66-251 MA)

  • “Life Rebounding” 

  • Sea temps rose

  • Fauna: Slow recovery of marine diversity

  • Flora: Dominated by seeds (no flowers)

    • First evidence of flowering plants show, but they don’t dominate. 



4th Mass Extinction- Triassic/ Jurassic (201.3 MA)

  • End of triassic mass extinction

  • Killed 80% of all species

  • Release of CO2, global warming, and ocean acidification



Jurassic (145-201 MA)

  • Age of dinosaurs 

  • Saurischia: Pelvis like a lizard

  • Orinitschia: Pelvis like a bird



Cretaceous (66-145 MA)

  • Rise of flowering plants

  • Forests were diverse and dominated by flowering plants 



5th Mass Extinction (K/pg- 66 MA)

  • Killed 75% of all animals, including dinosaurs, invertebrates, and most marine reptiles.

  • Asteroid hits Earth and Mesozoic ends. 

  • Temp increases a lot

  • Birds + crocodiles survive. 



Cenozoic (66 MA- present)

  • The age of mammals

  • Geology and temps warm



Geology and climate

  • Continents break up

  • Climate: Slowly cools down temp

  • Retraction of big forests and expansion of grasslands 



Palogene (23-66 MA)

  • Modern coral reefs

  • Insects evolve + diversify

  • Grasses undergo adaptation radiation

  • Absence of dinosaurs

  • Proliferation of birds, mammals, and snakes

Mammals didn’t dominate at the beginning of cenozoic



Transition from mammal like reptiles to mammals

  • Teeth variety

    • Increased food variety

  • Acute hearing

    • Better hearing than reptiles

  • Locomotion

    • Move faster, use less energy

    • Went from sprawling gait -> erect gait

  • Extinction was the turning point in mammalian evolution



Fast diversification of mammals

  • In 10 million years, 4000 species of mammals evolved, including aquatic and land mammals.

  • 56 MA: 16 modern placental mammals appeared 

  • 35 MA: Modern families appeared

  • 23-34 MA: Climate changes from warm + moist to dry + cool 



Great American Biotic Interchange (2.7 MA)

  • North and South America biota switch places



Pleistocene (2.58 MA- 10 KA)

  • Homosapiens came to be (300 KA)



The Ice Age

  • End of the pleistocene 



Pleistocene Megafauna Extinction

  • Humans and climate change caused it

  • 33 out of 45 genera of large mammals became extinct



Anthropocene and 6th mass extinction

  • Viewed as a period where human activity has had the most dominant influence on climate/ environment. 





Biodiversity and Conservation



Learning objectives

1) Define the meaning of biodiversity, distinguish the possible ways of thinking about biodiversity, and criticize the problems of using species as the functional unit of biodiversity measures

2) Explain the concept of hotspots and the factors that regulate diversity

3) Cite and explain the key concepts of diversity and distinguish between them

4) Calculate the Shannon and the Simpson indices and critically evaluate their strengths and limitations

5) Argue about the importance and value of biodiversity

6) Reflect on the main threats to biodiversity and devise solutions to the biodiversity crisis



Adaptation = arose from natural selection



On average there is a direct positive correlation between the size of an area and the number of species it contains. The relationships are shown in a species area curve. 



Diversity and area

  • Habitat diversity

    • Contains more species in larger areas because they contain more habitats. 

  • Colonization

    • The number of species in an area may result from a dynamic balance between the number of species colonizing from the source pool (e.g. the mainland set of species for many islands), and those going extinct after colonization

  • Speciation/ Extinction dynamics 

    • If species with larger geographic ranges have a greater probability of speciating (perhaps because barriers are more likely to subdivide their ranges) and also have a smaller likelihood of extinction (because they contain more individuals, and chance events are less likely to influence them all simultaneously), then more species will accumulate.



Diversity and Energy

  • Areas where there is a higher incidence of solar radiation should have more energy available to life and, thus, more species.



Biodiversity Hotspots

  • High number of endemic species (unique to a specific place)



Measuring diversity (key concepts)

  • Abundance

    • Total number of organisms in a given area (quantitative) 

  • Richness

    • Total number of species in a given area (qualitative)

  • Evenness

    • A measure of how close in number each species are in a given environment

  • Diversity

    • Relationship between number of species and abundance in a certain area



Shannon Diversity Index




  • Where pi is the proportion of individuals of species (i) in the whole community

  • N is the number of individuals



Simpson Diversity Index


  • N= species abundance

  • n= species evenness




Value of Biodiversity

Direct Use

  • Food

  • Medicine

  • Ecotourism

  • Recreation

  • Industrial materials

Tragedy of the Commons

Indirect Use

  • Pest control

  • Pollination

  • Photosynthesis

  • Climate regulations 

Non-use

  • Preserve for future generations

  • Future use

  • Existence is useful to many members in our society

  • Moral obligation



Threats to biodiversity

  • Habitat loss

    • Caused by human settling/ harvesting resources

  • Overfishing

    • Usually in fisheries (Tragedy of the Commons)

  • Invasive Species

    • Outcompete and feed on others

    • Brings disease to endemic species

  • Climate Change

    • Rapid global temp change which makes zones uninhabitable to endemic species



What to do?

  • Gather data

    • Study biodiversity

  • Change human behavior

    • Legislation, international conventions

  • Preserve pristine areas

    • National Parks, etc. 

  • Habitat restoration

    • Reconstruct lost biodiversity

  • Preserve genetic diversity



Experimental Design



Learning Objectives

1) Identify the main steps of the process of designing an experiment

2) Explain the terms involved in an experiment such as: control, variables, etc.

3) Based on a question, propose a scientific hypothesis 

4) Design an experiment that can test a hypothesis, obeying the principles of scientific methodology (falsifiability and repeatability)



  • Observation (data/facts)

    • What you can see/smell/taste/hear/measure 

  • Inference (Hypotheses/ educated guesses)

    • Conclusions you can make given past knowledge/ context



Mendel

  • Observed

    • Different plants could be crossed and their offspring could have features of ancestors. 

  • Inference

    • How do plants inherit features of their parents?



Experimental design

  • Create an effective scientific experiment to answer a scientific question

  • Think about these…

    • Can my question be answered by my experiment?

    • Did someone answer this before?

    • Is the experiment feasible?

    • What are my variables?

    • How will my results confirm or refute my hypothesis?



Good characteristics of peas to experiment

  • Variety

  • Convenience

  • Numbers

  • Easy to cross



Planning the experiment

  • Need variables (things that can influence results)

    • Independent variables

      • Changed by scientists 

    • Dependent variables

      • Responds to independent variable

    • Controlled variables

      • Try to maintain and isolate them to stay the same 

  • Conditions (methodology and procedure)

    • Different number of treatments you’ll do

  • Control 

    • Treatment that you know beforehand the results

    • Positive control

      • Validates procedure 

    • Negative control

      • Negative outcome

  • Collect data and analyze results

    • Mendel concluded…

      • Hereditary traits are controlled by factors that exist in pairs

      • Factor spread randomly throughout the gametes

      • Some traits are stronger than others