Unit 8 and 9 Biology
Unit 8: Evolution
Key terms
Variation-Individual organisms demonstrate different traits
Adaptations-Some variation give an organism a survival advantage
Adaptations help organisms live longer and reproduce more
Inheritance Traits-Favorable traits that get passed down from the parent to the offspring
Fossil Record-Never complete, record of ancient past life
Biogeography-Study of where organisms lived and how their ancestors lived
Homologous Structure-Structures that are anatomically similar, but perform different functions
Example-A whale fin and a human arm
Analogous Structure-Structures that share the same functions but are not anatomically similar
Example-A bat wing and an insect wing
Vesitigial Structure-A structure that is evidence of the past. It does not serve a purpose now, but it did long ago
Example-The human appendix
Directional Selection-When an extreme trait helps organisms survive better, resulting in that trait becoming more common in the population
Larger beaks helps birds get more food and those birds will reproduce, so overtime the average beak size will increase over generations
Stabilizing Selection- When the average trait is best, and extreme traits are selected against
Example: Babies born at an average weight are more likely to survive
Disruptive Selection-When both extreme traits are favored, and the average trait is selected against
If only small and large seeds are available to birds,birds with small or large beaks will survive best, and birds with medium beaks will die off.
Fitness-How well an organism survives and reproduces\
Binomial Nomenclature-The two part naming system used to classify organisms
First name, genus, capitalized and italicized
Second name, species, lowercase and italicized
Gene pool-All gene variations within a population, where changes in allele frequencies over time signify evolution
Allele Frequency-How often a certain allele appears in a population
Genotype frequency-The frequency a genotype appears in a population
Population-A group of individuals of the same species that live in the same area and interbreed
Environmental Pressures-Factors in an organism's surroundings (biotic like predators/food, or abiotic like climate/water) that favor certain traits, leading to natural selection and shaping a population's characteristics over generations
Key People
Charles Darwin (1809-1875)-The father of evolution
Voyaged to the South American coast, and specialized in studying the variation of finches beaks
James Hutton (1726-1797)-Proposed ideas about geological processes being slow, and came to the conclusion that the earth is much older than we thought
Jean-Baptist de Lamarck (1744-1829)- Believed organisms could change if they needed to change
Thomas Malthus (1766-1834)-Believed Earth had a carrying capacity and once capacity was reached there would be a population crash
Charles Lyell (1797-1875)-Father of geology and uniformitarianism. Meaning geological changes occur at the same rate today as they did millions of years ago
Carolus Linnaeus- Developed binomial nomenclature
Evolution
Evolution-The gradual change in the heritable characteristics (genes) of biological populations over successive generation
Evidence of evolution is found in fossil records, biogeography, homologous structures, vestigial structures, and molecular evidence
Natural selection and genetic drift are mechanisms of evolution
Individuals don’t evolve, populations do overtime
For a population to evolve there must be environmental pressure and variation
Source of Genetic Variation
Mutations-Random changes in DNA that can introduce new genetic variations
Sexual reproduction-Increases the genetic variety through recombination
Environmental pressure-Variations must exist for natural selection to occur effectively
Key Concepts in Darwin’s Theory
Natural selection
Heritable variations exist within populations
Organisms compete for limited resources
Some individuals possess adaptive traits that enhance survival and reproduction
Over generations, adaptive traits become more common in the population
Natural Selection
Natural selection is a mechanism of evolution
Organisms with higher fitness will survive
Natural selection is a process where organisms that have traits that help them survive and reproduce are more likely to survive and pass those traits onto the next generation
AKA survival of the fittest
Organism best suited to their environment means they will live longer and reproduce more
Mutations and variations within an organism are completely random
Neutral- Mutations and variations will have no effect on the organisms fitness
Negative-Mutations and variations negatively affect an organisms fitness, meaning that organisms will not have many babies, so the trait won’t be passed down
Positive-Mutations and variations positively affect and organisms fitness meaning that that organism will have many offspring because that trait helped them survive and reproduce
Genetic Drift
Genetic drift is a change in allele frequencies due to chance
An example-A few bugs in a population getting run over by a bike
Genetic drift is completely random and has nothing to do with fitness
Bottleneck Effect-When the size of a population is suddenly and drastically reduced in size
Example-A forest fire destroys many trees, but the trees it did not destroy were lucky, and are not a full representation of the whole population. Due to the new, smaller population there is likely to be a change in allele frequencies
Founder Effect-Organisms that found a new area to live
The organisms that arrive to the new environment does not represent the original population in which they came from
Genetic drift highly impacts small populations rather than large ones because if a few individuals randomly die, their genes can be lost completely.
Speciation
Species-Can interbreed with each other and its offspring can reproduce
2 different species can breed together and have offspring, but the offspring won’t be fertile
Speciation-The development of new species
Often occurs when species are isolated from each other
Allopatric Speciation-A geographic barrier separates the populations
Barriers like mountains, rivers, etc.
The barriers prevent the species from interbreeding, in turn preventing them from sharing the same gene pool
Overtime the populations can significantly change genetically, not allowing them to interbreed even if they were brought back together
Sympatric Speciation-Speciation occurring in the same area
Prezygotic barrier-A barrier that does not even allow fertilization to occur
Behavioral Isolation-When two populations don’t mate because their behaviors are different, even though they could physically mate
Ex-Birds having specific mating songs that attract a new bird species to mate with them
Temporal Isolation-When species breed at different times of the year
Ex-Two species of frog that live in the same pond, but one breeds in early spring and the other breeds in late summer, so they don’t interbreed
Habitat Isolation-When species live in 2 different habitats so they can’t interbreed
Ex-One frog lives in a pond and the other lives on land
Post Zygote barrier-A barrier that occurs after the offspring is fertilized
Offspring cannot reproduce
Offspring are too weak and cannot survive long after birth
The offspring cannot develop even in embryonic stages
Isolation itself is not a mechanism for evolution like natural selection and genetic drift
Isolation separates the gene pool of species
Taxonomy
Branch of biology focusing on identifying and classifying organisms
Domain
Archaea, bacteria, eukarya
Kingdoms
Plants animals, fungi, prostisia, eubacteria, and archaeobacteria
Phylum
Class
Order
Family
Genus
Species
Phylogeny and Evolutionary relationships
Phylogeny-The evolutionary history of organisms, emphasizing the their common ancestors
Cladistics-Method of classifying organisms based on their evolutionary relationships
Hardy-Weinberg Equilibrium
Hardy-Weinberg equilibrium describes a situation in which a population’s allele and genotype frequencies are constant unless evolution is acting upon them
If real-world data does not match Hardy-Weinberg equilibrium then the population is evolving
When solving either Hardy-Weinberg equation ensure to use the recessive allele over the population size if not given the p and q values
Allele frequencies are constant
Genotype frequencies are constant
Evolution is not occuring
Five Conditions for Hardy-Weinberg Equilibrium
The population must be very large
Mating must be random
There can be no migration (movement into or out of the population)
There can be no mutations
There can be no natural selection (no advantage to any trait)
Hardy-Weinberg equation for allele frequencies
p+q=1
Use when given allele frequencies
Ex-0.6 of dominant allele and 0.4 of recessive allele
p represents the dominant allele
q represents the recessive allele
Hardy-Weinberg equation for genotype frequencies
p^2+2pq+q^2=1
Use when given an individual
p^2 is homozygous dominant frequency
2pq is the heterozygous frequency
q^2 is the recessive frequency
Unit 9: Ecology
Key Terms
Ecology-Scientific study of interactions among organisms, populations, and communities and their interactions with the environment
Biotic factors-All living organisms in an environment
Ex-Grass, algae, mushroom, cat, etc.
Abiotic factors-All the nonliving things found in an environment
Ex-Air, soil, temperature, sunlight, etc.
Atmosphere-The region of earth containing all the gasses
Biosphere- All living organisms on earth
Hydrosphere-All of earth’s water (lakes, ponds, oceans, etc.)
Geosphere-All of earth’s rock, minerals, landforms, etc. (Terrestrial part of earth)
Climate-Patterns and average of temperature, precipitation, clouds, and wind over MANY YEARS
Weather-Consists of SHORT TERM changes in temperature, precipitation, clouds, and wind from day to day
Salinity-Salt concentration
Demography-The study of human populations
Primary Succession-Occurs only on bare rock. Bare Rock can be created by volcanic explosions, or glaciers retreating
Pioneer Species-are the first organisms to colonize newly formed rock areas
Biological Levels of Organization
Atom-Smallest unit of matter that is pure (carbon, oxygen, etc.)
Molecules-Groups of atoms (water, DNA, etc.)
Organelle-Specialized parts inside cells (nucleus, mitochondria, etc.)
Cell-Smallest unit of life (Muscle cell, plant cell, etc.)
Tissue-Group of similar cells working together (muscle tissue, xylem, etc.)
Organ-Different tissues working together for a function (root system, circulatory system, etc.)
Organism-One individual living thing (human, tree, etc.)
Population-Members of the same species in one area
Ecosystem-A community plus abiotic factors
Biome-Large regions with similar climate and life
Biosphere-All life on Earth and where it exists
Greenhouse Effect
The greenhouse effect is a natural process that keeps Earth warm enough for life
How it works
Sunlight passes through Earth’s atmosphere and warms the surface
The Earth gives off heat (infrared radiation)
Greenhouse gases (like carbon dioxide, methane, and water vapor) trap some of this heat in the atmosphere
This trapped heat keeps the planet warm, like a blanket
Importance
Without the greenhouse effect, Earth would be too cold for most life
It keeps temperatures stable enough for plants, animals, and ecosystems
Problem with the Greenhouse Effect
Human activities, like burning fossil fuels and deforestation add extra greenhouse gases
This causes more heat to be trapped, leading to global warming and climate change
Sun in →heat out→gases trap heat→Earth stays warm
Biomes
Tundra
Climate and weather
Very cold; long winter, short cool summers
Precipitation
Very low ≤ 10 inches per year, mostly snow
Key traits
Permafrost (ground [soil, rock, sediment] that stays frozen), treeless, short growing season
Plants and Adaptions
Mosses, lichens, grasses
Non vascular plants and shallow roots
Animals and Adaptations
Arctic fox, caribou, polar bear
Thick fur, fat (blubber) for insulation
Taiga
Climate and weather
Cold winter, mild summers
Warmer and wetter than the Tundra
Precipitation
Moderate, 12-30 inches per year, mostly snow
Key traits
Coniferous forest (dominated by cone-bearing evergreen trees), acidic soil
Plants and Adaptations
Pine, spruce, fir
Needle like leaves to reduce water loss
Animals and Adaptations
Moose, wolves, bears
Thick fur and hibernation
Temperate Deciduous Forest
Climate and weather
Four seasons; warm summers, cold winters
Precipitation
Moderate, 30-60 inches per year
Key traits
Broad leaf trees, rich fertile soil
Plants and adaptations
Oak trees, maple trees
Leaves drop during the cold season to conserve water
Animals and adaptations
Deer, foxes, birds
Migration to other places, seasonal coats
Grassland
Climate and weather
Hot summer, cold winters
Wet season and dry season
Precipitation
Low-moderate, 10-30 inches per year
Key Traits
Broadleaf trees, fertile soil
Plants and adaptations
Grasses, grains
Deep roots resist fire and drought
Animals and adaptations
Bison, prairie dogs
Grazing teeth, burrowing (making a hole)
Desert
Climate and weather
Very hot or cold; extreme temperatures swings
Dryest biome
Gets cold at night
Precipitation
Very low < 10 inches per year
Key Traits
Dry soil, sparse vegetation
Plants and adaptations
Cactus, succulents
Thick cuticle, water storage
Animals and adaptations
Lizards, snakes, kangaroo rats
Nocturnal, conserve water
Tropical Rainforest
Climate and weather
Warm year-round, very humid
Closest to the equator
Precipitation
Very high, 80-160 inches per year
Key traits
High biodiversity
Layered canopy
Poor nutrient soil
Plants and adaptations
Broadleaf trees, vines
Drip tips shed water
Many roots are above ground
Animals and adaptations
Monkeys, birds, insects
Camouflage, arboreal life (living in or among trees)
Freshwater-Low salinity (rivers, lakes, wetlands)
Rivers and streams
Flowing freshwater=Rivers and streams
Still freshwater=Lakes and ponds
Climate and weather vary by region
Water moves slower in a river and debris settles on the bottom
Because of this, rivers tend to have more nutrients and less dissolved oxygen
Precipitation depends on region
Flowing water, high oxygen
Algae, moss
Fish, insects
Lakes
Larger and deeper than ponds
Plant growth is limited to the shoreline
Sunlight does NOT penetrate to the bottom= no plants after a certain depth!
Water lilies, algae
Fish, frogs
Ponds
Small, shallow bodies of water
Sunlight penetrates all the way to the bottom
Most completely filled with plant material
Very high amount of nutrients
Wetlands
Climate and weather varies
High precipitation
Saturated soil, nutrient rich
Cattails, grasses
Root adapted to low oxygen
Bird, amphibians
Saltwater-High salinity (oceans, reefs, estuaries)
Oceans
Stable temperatures
Indirect precipitation
Largest biome, depth zones
Phytoplankton (producer in water biomes, and the start of many food chains)
Fish whales
Pressure tolerance, countershading
Coral Reefs
Warm, tropical climate
Indirect precipitation
Shallow, high biodiversity
Algae
Coral, reef fish
Camouflage symbiosis
Estuaries-Transition zone
Moderate climate and weather
Precipitation is moderate to high
Mixture of fresh and salt water
Mangroves, grasses
Crabs, oysters
Tolerance to salinity changes
Seashores-Tides have a huge influence on life here
Intertidal Zone-Portion of the shoreline that is covered with water at high tide and exposed to the air at low tide.
Can be sandy or rocky
Small fish, clams, crabs, other mussels are trapped in the TIDAL POOLS during low tide
Limiting factors in water biomes are amount of salt (salinity), amount of dissolved oxygen, and sunlight
Light Zones in Aquatic Biomes
Pelagic Zone
Open water away from the shore and bottom
Can be photic or aphotic
Includes most swimming organisms
Fish, whales, plankton
Photic Zones
Top, thin layer of water
Sunlight reaches here
Photosynthesis happens
Most life is found here
Includes phytoplankton, algae, many fish
Aphotic Zone
Below the photic zone
Little to no sunlight
No photosynthesis
Animals relying on falling food for chemosynthesis
Disphotic (twilight zone)
Between photic and aphotic
Dim light, not enough for photosynthesis
Benthic Zone
Bottom of the body of water
Can be in light or dark areas
Crabs, worms, clams
Energy Flow in an Ecosystem
Energy flows through the ecosystem by an organism eating another organism or by a decomposer breaking down another organism
Trophic Level-An organism's position in a food chain or web, showing how energy flows from producers (plants) up through various consumers (herbivores, carnivores) to the top predators
10% Rule
10% of the energy “harvested” at a lower trophic level is transferred up to the next higher trophic level
The other energy that is not transferred energy is lost as heat in the environment
Law of energy conservation-Energy cannot be destroyed or created it can only be transformed from one form to another
Food chain
Shows the energy flow in one direction through the ecosystem
Food web
Shows the interconnected relationship between organisms
Organisms affect each other because if one organism is taken out of the web other organisms will be affected
Levels of consumers
Producer-Autotrophs, make their own food
Primary consumers-Herbivores that eat plants
Secondary consumers-Carnivores and omnivores eating primary consumers
Tertiary-Carnivores eating secondary consumers
Apex predators-Top predators of the web/chain
Biogeochemical Cycles
Water cycle
Evaporation: The sun heats water in oceans, lakes, and rivers, turning it into water vapor (a gas) that rises into the atmosphere.
Transpiration: Plants release water vapor from their leaves, adding to atmospheric moisture. (Evaporation + Transpiration = Evapotranspiration).
Condensation: Water vapor in the air cools as it rises, changing back into tiny liquid water droplets or ice crystals, forming clouds.
Precipitation: When clouds become saturated, water falls back to Earth as rain, snow, sleet, or hail.
Collection/Runoff/Infiltration:
Runoff: Water flows over land into rivers, lakes, and eventually the ocean.
Infiltration: Some precipitation soaks into the ground, becoming groundwater.
Carbon Cycle
Photosynthesis: Plants, algae, and some bacteria take CO2 from the atmosphere and convert it into organic matter (glucose) using sunlight, storing carbon.
Respiration: Organisms release CO2 back into the atmosphere or ocean as they use glucose for energy.
Decomposition: Bacteria and fungi break down dead organic matter, returning carbon to the soil, air, or water.
Ocean Exchange: CO2 dissolves in and is released from the ocean, reacting with water to form bicarbonate, with the ocean absorbing much of the excess from the atmosphere.
Geological Processes: Carbon is stored in rocks (limestone) and sediments, released slowly through volcanic activity, and buried long-term in coal and shale.
Nitrogen Cycle
Nitrogen Fixation: Inert atmospheric nitrogen (N₂) is converted into ammonia (\(NH_{3}\)) or ammonium (\(NH_{4}^{+}\)) by nitrogen-fixing bacteria (in soil or roots) or lightning.
Nitrification: Soil bacteria further convert ammonia into nitrites (\(NO_{2}^{-}\)) and then into nitrates (\(NO_{3}^{-}\)), a form plants readily absorb.
Assimilation: Plants absorb nitrates (or ammonium) through their roots, incorporating nitrogen into organic molecules like proteins and DNA. Animals get nitrogen by eating plants or other animals.
Ammonification: Decomposers (bacteria, fungi) break down dead organic matter (plants, animals, waste), returning nitrogen to the soil as ammonia.
Denitrification: Denitrifying bacteria convert nitrates back into nitrogen gas (N₂), returning it to the atmosphere, completing the cycle.
Phosphorus Cycle
Weathering & Erosion: Phosphate (PO₄³⁻) is released from rocks by rain and erosion, entering soil and water. Volcanic ash and mining also add phosphorus.
Absorption by Plants: Plants absorb dissolved inorganic phosphorus from soil and water through their roots.
Consumption by Animals: Phosphorus moves up the food chain as animals eat plants or other animals.
Decomposition: Decomposers (like fungi) break down dead organisms and waste, returning phosphorus to the soil or water.
Sedimentation: Phosphorus in water eventually settles at the bottom, forming sediment that can become rock over geologic time, effectively removing it from the cycle for long periods.
Populations
Range-Where an organism can live
Growth Rate-How many organisms are coming and going in the population
Factors include-Birth, death, immigration, emigration
Density-The number of individuals per unit area
(number of people per square mile)
Distribution-How a population is spread out throughout an area
Clumped-Organisms travel together, and are clumped close together
Random-Organisms/seeds are like blown by the wind
Uniform-Organisms are evenly spread out throughout an area
Age Structure-The age of individuals, male or female, reproductive range
Carrying Capacity-Refers to the number of individuals that the environment can support
Logistic growth-Occurs when a population reaches carrying capacity for its environment
Exponential growth-A population rapidly reproduces (doubling each generation), often surpassing the environment's carrying capacity.
Population crash-When the population exceeds the amount that an environment can support causing the population to die off due to lack of resources
R-strategist-An organism who reproduces at a rapid rate
Produces thousands of offspring at a time (most lay eggs)
Ex-Insects
K-strategist-An organism who invests energy in carrying their young
Only has 1-2 babies at a time
Ex-Kangaroo
Limiting Factors
A limiting factor is any factor that controls the growth of a population
Limiting factors can be abiotic or biotic
Density Dependent Limiting Factors
Depends of the size (aka density) of the population
Ex-Competition, Parasitism and Disease, Stress from overcrowding, Predation & Herbivory, Humans as Predators
Density Independent Limiting Factor
Has nothing to do with the size of the population, and if the population was bigger or smaller the result would still be the same
Ex-Environmental Extremes- including weather; such as hurricanes, droughts, and floods, or disasters such as wildfires.
Habitats
Where an organism lives with a combination of physical and biological environmental factors that affect which organisms can live within it. (like an address)
Range of tolerance-The variety of environmental conditions within which it can survive and reproduce
When conditions are outside the zone of tolerance organisms experience stress and produce fewer offspring
Tolerance factors include-Temperature, Food Availability, Shelter, Water, other resources
Niche
The specific role that an organism plays in its environment
All organisms have different niches from each other primarily due to competition
Species Interactions
Species interaction in numerous ways that help the ecosystem function
Competition-When more than one organism attempts to exist in the same niche (use the same resources) as another, competition occurs.
Interspecific competition- Two Different species competing.
Intraspecific Competition- the members of the same species competing
Competitive Exclusion Principle- No two species can inhabit exactly the same niche at exactly the same time. One species will be better at competing for and acquiring resources
Predator-Prey Dynamics-The relationships between predator and prey are intertwined.
Keystone Species- A species that plays such an important role in its habitat that the increase or decrease GREATLY affects all other organisms in that habitat
Symbiosis-Organisms that live very close together and have an interdependent relationship on each other
Mutualism-Both organisms benefit from the interaction
Ex-Bees pollinating flowers
Commensalism-One organism benefits and the other is unaffected
Ex-Barnacles on a whale
Parasitism-One organism benefits and the other is harmed
Ex-Ticks on a deer