Bio Honors Unit 1

8 characteristics of life

8 characteristics of life

Made of cells, response to stimuli, metabolism, reproduction, adaptation through evolution, homeostasis, grows and develops, contains DNA

Metabolism

chemical reactions in cells that change food into energy

Homeostasis

The maintenance of stable internal conditions in an organism

Experiment

A scientific test, carried under controlled conditions that involve changing one factor to see the effects

Cell

A basic unit of living matter separated from its environment by a plasma membrane; the fundamental structural unit of life

artificial selection

The selective breeding of domesticated plants and animals to promote the occurrence of desirable traits

Gene

A unit of hereditary information made of specific nucleotide sequences in DNA/RNA. Most are found in chromosonal DNA; few are carried by mitochondria/chloroplasts

systems biology

Biology that aims to model the behavior of an entire biological system by studying the interactions between parts

natural selection

A process in which individuals with certain inherited traits are more likely to survive and reproduce than the undesired

gene expression

the process by which genetic information flows from genes to proteins; the flow of genetic information from the genotype to the phenotype

evolution

Descent with modification; living species are descendants of ancestral species that were different than present-day ones; the genetic changes in a population over generations

controlled experiment

An experiment in which an experimental group is compared with a control group, only factor that is tested is changed

Darwin’s Theory of Evolution main points

1. Individuals in a population vary and have heritable traits

2. Resources create competition to survive and reproduce

3. Individuals with ideal traits are more likely to S+R

4. Over time, natural selection occurs and species evolve

cellular respiration

The process by which cells convert glucose and oxygen into energy, carbon dioxide, and water

Mutation

Changes in the DNA sequence of an organism's genome that can lead to variations in traits

Why were protocells important?

Once protocells came to existence chemical reactions were facilitated, eventually could have led to self-replicating “genes” occuring to allow natural selection to advance life

speciation

the formation of new, distinct species by evolution

speciation event

A process where a single species evolves into two or more distinct species, often due to isolation and genetic divergence

prokaryotic

Refers to single-celled organisms that lack a nucleus and membrane-bound organelles, such as bacteria and archaea

eukaryotic

refers to cells that have a nucleus and membrane-bound organelles, ex. plants, animals, fungi, and protists. Always aerobic

anaerobic

absent of oxygen

fossil

Preserved remains, impressions, or traces of ancient organisms

paedomorphosis

The retention in an adult body of juvenile features of its evolutionary ancestors

monophyletic

Pertaining to a group of taxa that consists of a common ancestor and all its descendants, equivalent to a clade

convergent evolution

The evolution of similar features in different evolutionary lineages

geologic record

time scale established by geologists that divides Earth’s hitory into eons: Hadean, Archean, Proterozoic, Phanerozoic. the eons are subdivided into eras, periods and epochs

clade

A group of species that includes an ancestral species and all its descendants

analogy

The similarity between two species due to convergent evolution rather than descent from a common ancestor

phylogeny

The evolutionary history of a species/group of related species

Pangea

the supercontinent that formed near the end of the Paleozoic era, when plate movements brought all the landmasses of Earth together

molecular systematics

The scientific discipline that uses nucleic acids or other molecules in distinct species to infer evolutionary relationships

biogeography

The study of past and present distributions of organisms

Eukarya

domain of life that includes all eukaryotic organisms

Archea

One of two prokaryotic domains of life

Bacteria

One of two prokaryotic domains of life

cladistics

A method of classifying organisms based on common ancestry and evolutionary relationships, using a branching diagram called a cladogram.

Taxonomic Category order?

“Doctor King Phillip Came Over For Great Soup”

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

parsimony

the search for the least complex explanation for an observed phenomenon (in phylogenetic trees, fewest evolutionary changes)

molecular clock

some regions of genomes evolve at constant rates, so estimates of time required for an evolutionary change can be made

outgroup

In a cladistic study, a taxon/group of taxa closely related to but known to have diverged before the lineage that contains the group of species being studied

taxon (plural taxa)

A named taxonomic unit at any given level of classification

macroevolution

Large-scale evolutionary changes that occur over long periods, resulting in the emergence of new species or major shifts in traits.

microevolution

Small-scale evolutionary changes within a species or population, often involving changes in allele frequencies over time.

shared ancestral character

A character shared by members of a particular clade that originated in an ancestor outside of the clade

shared derived character

An evolutionary novelty that is unique to a particular clade

ingroup

A group of taxa whose evolutionary relationships are being determined within a cladistic study

stromatolite

Layered rock that results from the activities of prokaryotes that bind thin films of sediment together

taxonomy

The scientific discipline related to identifying, naming and classifying forms of life

phylogenetic tree / cladogram

A branching diagram that represents a hypothesis about the evolutionary history of a group of organisms

radiometric dating

A method for determining the absolute ages of fossils and rocks, based on the half-life of radioactive isotopes

plate tectonics

the theory that the continents are part of great plates of the Earth’s crust that float over the mantle. Movements in the mantle cause these plates to move slowly over time

Age of Earth

4.6 billion years old

How was primitive Earth?

• Molecular oxygen (O₂) is missing from the atmosphere in primitive earth.

• So hot that all H₂O only existed in gas

• Lightning, earthquakes/volcanic

• Oceans formed after the cooling down of the earth.

Miller and Urey experiment

an experiment made trying to simulate the atmosphere of ancient Earth, resulted in the formation of amino acids

amino acids

Organic molecules that are the BUILDING blocks of proteins

Amino acids to protein hypotheses (2)

1. Amino acids could have been collected in “pools”, with an energy source allowing them to join together to create the first proteins (Sidney Fox)

2. Amino acids were put together by radioactive molecules in old clay (earth). (Graham Cairns-Smith)

RNA compared to DNA

• RNA is theorized to be the first genetic material before DNA, because it self-replicates on its own

• DNA needs enzymes, proteins, etc- RNA does not

• RNA is unstable, does not stay in the same structure under different conditions like DNA does

Summary of the genesis of life

Earth → Inorganic molecules → Organic molecules
→ ”Protocell” → Cells

protocells

Structures made of organic molecules with a membrane, resembling cells but without their complex structures and functions like genetic material replication

cyanobacteria

Photosynthetic bacteria, also known as "blue-green algae," that produce oxygen and are believed to be among the earliest organisms to perform photosynthesis

What happened after photosynthesis came to exist?

Oxygen entered the sea and atmosphere, and an ozone layer was formed in the atmosphere as well

Oxidizing atmosphere

• atmosphere with enough oxygen atoms in the atmosphere for aerobic respiration (opposite is reducing atmosphere)

• However, containing free O₂ inhibits formation of complex organic molecules

How were the first cells?

First cells were aerobic, photosynthetic, prokaryotes

Endosymbiotic Hypothesis - “The Big Gulp”

• Mitochondria were probably once free-living aerobic prokaryotes

• Chloroplasts were probably once free-living photosynthetic prokaryotes

• Modern bacteria is around the size of mts/chloros, m mitochondria/chloroplasts have their own “membrane”

• A nucleated cell probably engulfed these prokaryotes that became various organelles, a symbiotic relationship formed that became advantageous over time

What lifeforms came into existence in the Cambrian period?

invertebrates: Animals without a backbone or spinal column

relative dating of fossils

dates fossils based on their relationships to other fossils (older/younger) (inaccurate)

Lamarck

• first scientist to state the idea that organisms change over time. He was wrong on how they change

  • Lamarck believed that the change happened during their lifetime

  • Experiments do not uphold Lamarck’s inheritance of characteristics

  • Around 100 years before DNA’s discovery, people had no idea

Lyell

•  geologist

  • Uniformitarianism: Darwin takes away that the Earth is very old.

  • Darwin was aware that his theories needed a lot of time

Malthus

• economist

  • There is a finite number of resources, some have more and some have less

  • Limited amount of biological resources, those who get it survive

  • Carrying capacity: there is a limit of organisms that can live in one place

Natural selection FORMULA

• If everyone is the same, natural selection has nothing to work on

• Heritable Trait (DNA) + Variation + Selective pressure + Differential survival and reproduction = NS

Selective pressure

Environmental factors that favor certain traits over others, influencing the survival and reproduction rates of organisms with those traits

Differential survival and reproduction

The concept that individuals with advantageous traits are more likely to survive and reproduce, passing those traits to the next generation

Population genetics

The study of genetic variation of populations and how allele frequencies change over time due to selection, mutation, gene flow, and genetic drift

Gene pool

The total collection of alleles and their frequencies in a population at a given time.

Darwin’s idea of complex evolutions

Darwin: Complex characteristics (e.g eyes) can evolve but will be imperfect, because evolution works with what it has.

Extinction

The complete disappearance of a species or group of organisms from Earth

When does extinction occur?

Environmental changes, habitat loss, competition, disease, inability to adapt

How does natural selction affect diversity?

Natural selection decreases diversity, through the preference of certain variations over time

Darwinian Fitness

The ability of an organism to survive, reproduce, and pass its genes to the next generation compared to other organisms in the population

Evidence of evolution

1. Fossils (display transitions between species)

2. Anatomical (exist when species are closely related)

3. Embryological evidence (shows common ancestry, and differences happen during development)

4. Biochemical evidence (Darwin did not use, DNA was not yet discovered)

   • Looks at DNA and amino acid sequences. Closer DNA = closer relations

Homologous structures

Structures shared between species that are used for different functions (ex. limbs). Evidence of common ancestry

Analogous structures

Analogous structures: Different structures existing with the same function (ex. wings). NOT evidence of common ancestry

Vestigial structures

Used by an ancestor but not anymore, no selective pressure to remove the structure, NS does not evolve it away (ex. wisdom teeth, appendix). Evidence of common ancestry

Embryo

Unborn/unhatched offspring

anatomical

Relating to the structure or organization of living organisms' bodies or their parts

genetic drift

A change in allele frequencies due to random chance (small populations)

gene flow

 Genetic exchange due to migration

gene locus

The location of a gene on a chromosome

Bottleneck effect

Environmental events reduce populations + genetic variability

Founder effect

Few individuals from a larger group enter an isolated area, rare alleles occur at high frequencies in the isolated population. (Aa*Aa can to create aa, can cause recessive inbreeding)

Directional selection

Favors one extreme phenotype, causing a shift in the population's traits in that direction (ex. camo colors)

Stabilizing selection

Favors intermediate phenotypes and reduces variation by selecting against extreme traits (ex. newborn head size)

Disruptive selection

Favors extreme phenotypes at both ends of the spectrum, leading to increased variation and potentially the formation of new species (ex. finch beak sizes splitting into new species)

Biological species concept

A species is defined as a population of individuals whose members can interbreed and create viable, fertile offspring

Reproductive Barriers

factors that prevent 2 species from reproducing

zygote

The cell formed by the union of sperm and egg, which develops into an embryo

Prezygotic Barriers

Occur before fertilization, preventing the formation of a zygote

• Habitat: Different habitats

• Behavioral: signals that attract mates

• Temporal: different times of existence

• Mechanical: anatomically incompatible

• Gametic: Egg and sperm are not compatible

Postzygotic Barriers

Reproductive barriers that occur after fertilization, affecting the development or viability of the offspring

• Reduced Hybrid Fertility: Hybrid are completely sterile

• Hybrid Breakdown: Offspring of hybrid have reduced v/f (grandchildren)

Allopatric speciation

New species form when populations are geographically separated, leading to genetic divergence.

Sympatric speciation

New species form within the same geographic area due to factors like genetic mutations or ecological niches.