Life's basics Flashcards
steps of the scientific method
- observation
- hypothesis
- new observations or experiments
- develop a theory
observation
Recorded as data - quantitative or qualitative
Microscopes, precision instruments etc.
Use statistics to determine if data is significant or random fluctuations
Inductive reasoning - generalisations derived from a large number of specific observations eg. The sun always rises in the east
hypothesis
possible explanations from observations that lead to a testable prediction
Can carry out an experiment (test under controlled conditions)
Deductive reasoning: “if”…”then” logic that flows on from premises.
Can never be proven true
Validity is increased when many scientists test the hypothesis and it stands up to experimentation
Predictions (based on hypothesis)
new observations or experiment
to test hypothesis
If results are not consistent, reject or revise hypothesis
If there is a change, hypothesis is correct (not necessarily correct) - come up with a new prediction to check again
develop a theory
when multiple related hypothesis have been supported, it is a theory.
Broader than a hypothesis
Vast amount of evidence
Can be modified or rejected
model organism
a species that is easy to grow in a lab and can be experimented upon (all living things are evolutionary connected).
what are the two types of studies?
observation and experimentation
experimentation
Test 2 or more groups in controlled conditions (truly assess impact of one variable - IV)
IV
what you change (in the experimental group)
DV
what you measure
controlled variable
variables you keep the same - species of flower, height of flower so that only colour is tested
control group
without the IV to determine whether other factors (other than the IV) cause the change
graphs
x axis: independent variable eg. Colour of flower
Y axis: dependant variable eg. Average time spent at each flower
sexual dimorphism
males and females of the same species display different characteristics other than genitalia.
facts about widow birds and their sexual dimorphism
From Africa
Female: yellow-brown, plain looking (blends into grasses)
Males: long black tails and red wings, white shoulders
Males jump with fluffed feathers to attract females - highest and longest
Males compete to be most impressive
Female lays eggs in one of the many nests in the male’s territory
characteristics of living things
- complex with precise spatial organisation
- change in response to environment
- can reproduce to pass on genetic info
- evolve
- metabolism
define evolving
changing over generations in response to environmental pressure.
what is homeostasis
maintaining a stable internal environment in the face of changing external environments
what is ecology?
the study of how organisms interact with one another and their natural environment.
Trees requiring bees to pollinate them to produce a seed
The seed is eaten and taken away so that it can grow somewhere where it will not have to compete with the other tree
Evolution allowed for the selection of sweeter flowers and sweeter fruits so that the animals want them
first law of thermodynamics
Energy can neither be created nor destroyed; it can only be transformed from one form into another.
Total energy in the world is constant
Living things transform energy from the sun or chemical compounds - inputs and outputs
Move, reproduce, build cellular components etc.
Dissipated as heat
second law of thermodynamics
The degree of disorder (or the number of possible positions and motions of molecules) in the universe tends to increase.
Organising marbles into a row takes energy, so does organising a cell
Entropy: the amount of disorder in a system.
Some energy is used for organising the cell but the rest is released as heat.
Heat increases motion and therefore increases disorder - by releasing heat, cells keep with the second law
Entropy can decrease locally (in the cell) when heat released into the environment increases disorder outside.
the cell - definition and features
Cell: simplest entity that can exist as an independent unit of life- simplest form of life.
Every living thing is made of cells - one, to a few to many
Vary in size
Cells have a stable blueprint, a boundary between the outer environment and an ability to harness materials and energy from the environment
Three main features of cells - store and transfer genetic info, enclosed in a membrane and undergoes metabolism
what are nucleic acids?
Nucleic acids store and transmit information needed to grow, function and reproduce
Acts as a blueprint
Cells copy this information to reproduce
DNA
a type of nucleic acid Double stranded helix
Each stand is a varying sequence of four different molecules, connected end to end
This sequence encodes cellular info
Directs the formation of proteins - structural and functional molecule involved in shape, movement, chemical reactions etc.
DNA is replicated and passed onto progeny - mistakes can be lethal
Mutations: changes to DNA that arise in replication of from environmental impacts. They can be lethal or lead to variation and evolution.
RNA
- a type of nucleic acid
Single stranded
Proteins copy the DNA template strands into a different form (mRNA)
Transcription: copying the information and forming mRNA
Translation: specialised proteins read the mRNA strand and assemble a protein
what is the central dogma?
pathway from DNA to RNA to proteins
what is a gene?
a section of DNA sequence that corresponds to a specific protein
what is the plasma membrane and what does it do?
separates the living interior of a cell from its non-living environment
Controls movement of materials into and out of the cell (protects the cell)
Selectively permeable
Membranes also surround internal structures (organelles), compartmentalising
what is the nucleus and what do and don’t have them?
houses the cell’s DNA. Controls the cell.
Prokaryotes don’t have a nucleus
Eukaryotes have a nucleus
cytoplasm
the fluid and organelles within a cell.
prokaryotes - emergence, descendants, size, features
Emerged 4 billion years ago
Bacteria are descendants
Small size allows them to reproduce rapidly, and easily obtain energy and nutrients from diverse environments
Usually single celled
eukaryotes - emergence, ancestors, examples, features
2 billion years ago from prokaryotic ancestors
Animals, plants, fungi, protists (single celled microorganisms)
Single celled or multi celled
In multi celled organisms, cells may specialise to preform different functions
Today, Bacteria, Archaea and Eukarya are more accepted terms:
Bacteria and archaea do not have a nucleus and are prokaryotes
Eukarya have a nucleus and are eukaryotes
Archaea are single celled microorganisms that live in hostile environments
define metabolism
the conversion of energy from the environment into a form that is used by cells.
The chemical reaction that converts energy into different forms and and builds and breaks molecules
Sustain life
what is ATP?
an energy storing molecule.
are viruses life?
Infectious genetic material - DNA or RNA
Not actually cells - cannot metabolise or reproduce by themselves
enter host cells to replicate themselves but this does not mean that they can respond to the environment
Cells can lyse (in single celled organisms) and hundreds of viruses spill out and infect other cells
what are viruses?
Have DNA or RNA surrounded in a protein coat and sometimes a lipid envelope
Cannot harness energy from the environment - makes other things impossible
Cannot read and use the intro from their genetic material
Cannot move things across coats and envelopes
To replicate they require a cell
So not living
how do viruses infect things?
Binds to a cell’s surface
Inserts genetic material into the cell
Use the cell to make new viruses - sometimes lyse (or break) the cell and the new viruses can infect more cells
Sometimes the genetic material of the virus integrates with the DNA of the cell
what is a prion?
misfolded prion proteins intercepts a normal prion and it misfolds too (in neurons)
Spongy areas in brain form causing neurological problems like Mad Cow Disease
Can ingest the proteins from foods and rarely from bodily fluids
what is a girus?
giant viruses that have more genetic materials.
Can do some replication but still need a host cell
Pitho virus was reanimated after 30 000 years after being frozen in the Siberian permafrost
Can be reanimated
what are bacteria?
Prokaryotes
Simple cell structure with no real defined compartments
Divide and replicate in binary fission - split in the middle to form daughter cells
Often good for us - produce vitamins etc.
Flesh eating ones aren’t so good…
what are protozoan parasites?
Single celled
Have a eukaryotic cell structure - defined regions, nucleus and mitochondria
Parasites: live on or in hosts to the detriment of them eg. Plasmodium (malaria)
what are parasitoids?
Insects that lay eggs into another live insect
Larvae will grow and then eat out the host insect and emerge
why is COVID not alive?
It is a virus Cannot reproduce or metabolise Not cellular Not complex Needs a host to replicate
atom
the basic unit of matter.
element
contains only one type of atom.
118 elements
nucleus, protons, neutrons
Nucleus: positively charged and made up on neutrons and electrons.
Protons: positively charged particles
Neutrons: neutrally charged particles. The number in an atom can vary resulting in isotopes.
electrons. where?
Electrons: negatively charged particles that move around the nucleus.
Occupy orbitals: areas in space where the electron is most of the time.
2 electrons per orbital
Electrons further from the nucleus have more energy
Several orbitals at the same energy level are shells.
atomic mass
the mass of protons and neutrons combined.
molecule
atoms joined with other atoms
chemical bond
how atoms interact together.
why are bonds important?
Dictate structure and function of macromolecules eg. Protein folding
Breaking and reforming bonds allows for creation of new molecules
Breaking bonds gives energy that can be used by cells
why do we have so much H, C, N, O and P
Few protons so they can be compact
They can form covalent bonds with each other
Carbon is most important - can form four covalent bonds (tetrahedral), allowing for a diverse range of structures
Carbon makes up the main macromolecules
what are the four major molecules?
Carbohydrates
Proteins
Nucleic acids
Lipids
molecular orbital
a merged orbital, with the full compliment of electrons.
polar covalent bonds
Polar covalent bond: electrons are not shared evenly between atoms.
Soluble in water as water is also polar
electronegativity
a difference in the ability of atoms to attract electrons, leading to unequal sharing.
Increases left to right as protons increase, pulling electrons closer to the centre.
Results in some atoms being slightly more positive and slightly more negative
non-polar bonds
Non-polar bonds: when electronegativity of the atoms is similar.
Does not dissolve well in water
ionic compounds dissolved in water
When dissolved in water, the ions break apart and each one is surrounded by water molecules (negative parts of water bond with cations and vice versa)
van der Waals forces
Due to motion of elections in long, non-polar molecules
Produces asymmetry in distribution of electrons
Weak electrostatic attraction between molecules (weaker than ionic and covalent)
chemical reactions
Bonds between reactants are broken and new bonds form to create the products.
Energy is released from this process
hydrophilic vs hydrophobic
Hydrophilic: molecules that are also polar so dissolve readily in water.
Hydrophobic: molecules that are non-polar so do not dissolve readily in water.
properties of water
Water is a good solvent, and when solutes are dissolved, forms an aqueous environment.
hydrogen bonds - denotation, strength
Hydrogen bond: interaction between hydrogen atoms with a slight positive change and an electronegative atom of another molecule.
Denoted by a dotted lines
Hydrogen bonds form between two water molecules between slightly positive hydrogens on one molecule and slightly negative oxygens on another.
Weak bonds
ice
When frozen, water forms hydrogen bonds with four other water molecules, forming a crystalline structure
Ice is less dense than liquid water for this reason, hence why ice floats
Allows plants and fish to survive under the ice in winter (not frozen)
When ice heats, hydrogen bonds are destabilised and break, making the water more dense
cohesion
Cohesion: tendency to stick together
Caused by hydrogen bonds
High surface tension
Allows water to move through plants by transpiration
temperature
Increased temperature goes into trying to break hydrogen bonds instead of heating water considerably (causing molecules to move more)
More resistant to temperature changes (high heat capacity) - important for cells and global temperature (maintained by oceans)
high heat of vaporisation
Sweating is good for cooling
Takes a lot of heat energy to move away and evaporate - helps cool
pH
pH: measures the proton concentration.
In solutions of water, a small proportion of water molecules exist as protons and hydroxide ions.
pH = -log[H+]
pH ranges from 0 to 14
One pH unit corresponds to 10 fold hydrogen ions
Neutral at pH = 7 (proton and hydroxide ions are equal)
Reactions require strict pH
Acidic: when pH is lower than 7 and the concentration of protons is higher than that of hydroxide ions
Basic: when pH is above 7 and the concentration of hydroxide ions is higher than that of protons
parts of a microscope
Eyepiece: x10 magnification
Objectives: x4, x10, x40, x 100 (held by the turret)
Magnification: eyepiece x objective
Condenser: just under microscope stage, concentrated the light so that you can illuminate the specimen
Idris diaphragm: stops or controls the passage of light or controls the aperture (opening)
Closed: less light, increases the contrast of the specimen (especially if the cell is see-through - stained or not)
working out cell size
Field of view diameter at x400 (or whatever) divided by 25 cells across the field view
