Science Section 2 Flashcards
What is the focus of the section on Earth as a living planet?
The ways that life is organized from local to global scales
What are the major elements covered in the section?
- Evolution and Biodiversity
- Community Ecology
- Ecosystems
- Biomes
- Global Energy and Matter Cycles
What is biodiversity?
The diversity of all the genes, species, and habitats on Earth
How is biological diversity commonly measured?
By the number of different species in any given place
What does genetic diversity refer to?
The variety of genes within and among species
How many different genes do humans have approximately?
30000
What is a phenotype?
An individual’s anatomical, physiological, and behavioral characteristics
What is a genotype?
An organism’s unique genetic composition and the code for its phenotype
What are alleles?
Alternative forms of a gene that contain different instructions
What is the significance of mutations in genetics?
Mutations can produce new alleles and contribute to genetic diversity
What is fitness in biological terms?
A measure of the relative viability and fertility of an organism
True or False: The successful survival of more fit individuals leads to a change in the average phenotype of the species.
True
What is the process by which species evolve over time called?
Evolution
What is natural selection?
The process where individuals with advantageous traits are more likely to survive and reproduce
What are the key ideas of Darwin’s theory of natural selection?
- Organisms produce more offspring than needed
- Individuals express a range of phenotypes
- Some phenotypes enable better survival
- More fit individuals have better chances of reproducing
What is adaptation in the context of evolution?
The process of becoming most suited for a particular environment
What factors influence a species’ ability to adapt to environmental changes?
- How much change occurs
- How fast the change occurs
Fill in the blank: The observable characteristics associated with an organism’s genotype is called its _______.
phenotype
What can lead to the production of different phenotypes within a species?
Genetic diversity among individuals
What is the primary cause of new allele production?
Mutations
How does genetic variation relate to population size?
Larger populations usually have more genetic variation
What happens to alleles that are more harmful than beneficial?
They usually die out along with the individuals carrying them
What is the relationship between the sickle-cell allele and malaria?
The sickle-cell allele provides resistance to malaria but can cause severe health issues
What do adaptations include for plants in dry environments?
- Thick, fleshy leaves
- Thick waxy surfaces
What is the role of environmental changes in the adaptation of species?
Species must adapt through natural selection or may die out
What adaptations do plants have to conserve water?
Thick, fleshy leaves with thick waxy surfaces
These adaptations help plants serve and acquire scarce water.
How does the rate of environmental change affect species adaptation?
Species must adapt quickly to survive or risk extinction
Rapid changes may outpace a species’ ability to adapt.
What is gene flow?
Migration of individuals from one population to another, introducing new alleles
This can lead to new phenotypes in the receiving population.
Define genetic drift.
Random change in allele frequencies in small populations
It can lead to significant evolutionary changes without natural selection.
What is the bottleneck effect?
A drastic reduction in population size leading to reduced genetic diversity
This can occur due to hunting, habitat loss, or natural disasters.
What are the consequences of low genetic variation?
Increased risk of disease and low fertility
Examples include the cheetah’s low fertility and disease susceptibility.
How long can significant evolutionary changes take?
Hundreds to thousands of years
Smaller scale changes can occur over shorter time frames.
What three factors influence the pace of evolution by natural selection?
- Rate of environmental change
- Amount of genetic variation
- Population size
Small populations may evolve more quickly due to genetic drift.
What happens to species when the environment changes beyond their adaptability?
The population’s growth rate becomes negative and may lead to extinction
Migration or adaptation are often unsuccessful.
What is the fossil record?
Preserved remains of extinct organisms in rock
It provides insight into evolutionary history and extinction events.
What characterizes mass extinctions?
Large numbers of species die in a short time interval
Examples include the end of the Paleozoic Era and the K-T boundary.
What is currently believed about human activity and mass extinction?
We may be experiencing a human-caused mass extinction
This is largely due to habitat destruction.
How does habitat fragmentation impact biodiversity?
Reduces contiguous habitat and divides populations
This leads to genetic isolation and loss of genetic variation.
What are exotic species?
Species introduced to an area by humans, either deliberately or accidentally
They can disrupt local ecosystems and outcompete native species.
What is one example of an exotic species and its impact?
Zebra mussel
Introduced to the Great Lakes, it has depleted food supplies and caused ecological problems.
What can new housing developments cause?
Habitat destruction and/or fragmentation
When did the zebra mussel enter the Great Lakes?
During the 1980s
What is usually absent in new environments for exotic species?
Organisms that keep them under control in their native environment
What is ecology the study of?
The relationship between organisms and their environment
What three factors are critical to an individual’s survival in a particular area?
- Abiotic environmental conditions
- Availability of resources
- Habitat
What are environmental conditions?
Chemical or physical factors in the environment that influence survival and growth
What major conditions determine species presence in terrestrial systems?
- Availability of light
- Temperature
- Amount of precipitation
- Soil type
- Quantity of nutrients
What is the range of tolerance?
The range within which a given species will exist
What are resources in an ecological context?
Aspects of the environment that individuals use to stay alive
What is one example of a habitat with high biomass?
Salt marshes
What is interspecific competition?
Competition between individuals of different species for a limiting resource
What principle states that two populations that fill the same niche cannot coexist?
Competitive exclusion principle
What is the definition of a niche in ecology?
The role of an organism within a community
What are the three general ways populations of different species interact?
- Interspecific competition
- Predation
- Mutualism
What is predation?
The use of one species as a resource by another species
What is mutualism?
Interactions that increase the survival probability or reproduction of both species
What is a community in ecological terms?
Any assemblage of populations in a particular area or habitat
What summarizes the species that make up a community?
A food web
What are trophic levels?
Feeding positions in a food chain or web
What is a keystone species?
A species that plays a critical role in its ecosystem
Fill in the blank: The lowest trophic level is occupied by _______.
Primary producers
True or False: Only about 10 percent of the energy at one trophic level is passed along to the consumers in the next level.
False
What is the primary function of salt marshes in ecosystems?
Act as a nursery for many fish and shellfish species
What adaptations do salt marsh plants have to survive extreme conditions?
- Special tissues to excrete excess salt
- Air chambers in roots for oxygen production
What happens to populations when a limiting resource decreases?
The size of the population that depends on it also decreases
What is the role of predators in an ecosystem?
Limit the growth of prey populations
What is resource partitioning?
The division of resources to minimize competition between species
What happens to energy as it moves up trophic levels?
Energy is lost as heat, limiting biomass at higher trophic levels.
Define keystone species.
A species that plays a crucial role in its community, disproportionate to its abundance.
What are the three types of keystone species?
- Predators
- Ecosystem engineers
- Mutualists
How do predators function as keystone species?
By controlling the population of their prey.
Give an example of a keystone predator.
Sea otters maintain kelp forest ecosystems by preying on sea urchins.
What role do ecosystem engineers play?
They create or maintain habitats for other species.
Provide an example of an ecosystem engineer.
North American beaver transforms streams into ponds.
What are mutualists?
Species that interact for each other’s benefit.
What is an ecosystem?
A spatially explicit unit of the Earth that includes all organisms and abiotic components.
List the three important aspects of an ecosystem.
- Ecosystem boundary
- Biotic component
- Abiotic component
What does the abiotic component of an ecosystem include?
- Temperature
- Water
- Salinity
- Soil structure
- Mineral nutrients
What is the primary process in an ecosystem?
Flow of energy from the Sun through biotic and abiotic components.
How do environmental scientists define ecosystem boundaries?
By estimating the range of populations or particular ecological processes.
What is a disturbance in an ecosystem?
A process causing rapid injury or death of organisms and damage to the biotic component.
Differentiate between a disturbance and a perturbation.
Disturbance is rapid change; perturbation is a gradual change to normal values.
What is resilience in an ecosystem?
The rate at which an ecosystem returns to its original state after disturbance.
What are biomes?
Major regions of differing vegetation and wildlife types.
What factors are correlated with the presence of terrestrial biomes?
- Mean annual temperature
- Mean annual precipitation
Describe the tropical rainforest biome.
The wettest and warmest biome with high biodiversity and poor mineral nutrient soils.
What characterizes the temperate rainforest biome?
Tall coniferous trees, mild winters, heavy rain, and rich organic soils.
What is the primary vegetation in boreal coniferous forests?
Primarily conifers like spruces and firs.
Define temperate grasslands.
Areas where precipitation is insufficient to support dense forests, dominated by grasses.
What defines the desert biome?
Areas receiving less than 25 cm of precipitation per year.
What is the tundra biome?
An arctic region beyond the tree line with frozen soil and low productivity.
What are the two major types of aquatic ecosystems?
- Freshwater
- Marine
What is the benthic community?
Plants and animals living on or near the bottom of rivers and streams.
What major energy producer dominates lake and pond ecosystems?
Phytoplankton.
What is a thermocline in aquatic ecosystems?
An abrupt change in temperature of water with depth.
What percentage of the Earth does the ocean cover?
71 percent.
What is a significant limiting factor for marine ecosystems?
Uneven distribution of light and nutrients.
Fill in the blank: A keystone species can have a _______ effect on ecosystem health.
dramatic
What percentage of the Earth do oceans cover?
About 71 percent.
What are the major factors affecting marine ecosystems?
Uneven distribution of light and nutrients, depth, currents, and shoreline and bottom characteristics.
At what depths does peak species diversity in oceans typically occur?
About 2,000−3,000 meters.
What are upwellings in marine ecosystems?
Areas where nutrient-rich water rises to the surface, often due to wind patterns.
What are wetlands?
Transitional areas between terrestrial and aquatic ecosystems.
List three broad types of wetlands.
- Marine wetland (intertidal region)
- Estuarine wetland (where salt and fresh water mix)
- Freshwater wetlands
What is the water cycle?
The movement of water through the atmosphere and over the Earth’s surface.
What is evapotranspiration?
The combination of evaporation and transpiration.
What is the ultimate reservoir of water on Earth?
The ocean.
What are the four processes that drive the carbon cycle?
- Photosynthesis
- Respiration
- Decomposition
- Combustion
What is carbon fixation?
The process of converting carbon dioxide into organic compounds by plants.
What are fossil fuels?
Compounds like coal, oil, and natural gas formed from buried organic matter.
How is nitrogen critical for life on Earth?
It is a key component of amino acids, which are essential for all organisms.
What is nitrogen fixation?
The conversion of atmospheric nitrogen (N2) to a plant-available form (ammonium).
What process converts organic matter to ammonium?
Ammonification.
What is nitrification?
The two-step process of converting ammonium to nitrite and then to nitrate.
What is denitrification?
The natural conversion of nitrate to nitrous oxide (N2O) gas.
What is biodiversity?
The diversity of all genes, species, and habitats on Earth.
What is adaptation in the context of evolution?
The process of becoming most fit for a particular environment.
What is the current state of species extinction rates?
The Earth is in the beginning stages of a human-caused mass extinction.
What is community ecology?
The study of how populations interact within a biological community.
What are the three general ways species interact?
- Interspecific competition
- Predation
- Mutualism
What is a keystone species?
A species whose loss can lead to significant changes or extinction of an entire community.
What drives the interaction of living and nonliving components in ecosystems?
Global biogeochemical cycles of elements and nutrients.
What are ecosystems?
Specific places on Earth made up of interacting living (populations) and nonliving (climate, minerals, etc.) components.
What drives the interaction of an ecosystem’s living and nonliving components?
Global biogeochemical cycles of elements and nutrients.
What causes variation in the biotic components of a region?
Changes in temperature and moisture.
What are the ten major types of terrestrial biomes correlated with?
A region’s mean annual temperature and mean annual precipitation.
Name two types of environments distinct from terrestrial biomes.
Fresh water and marine environments.
What are considered the building blocks of life?
Water, carbon, and nitrogen.
Fill in the blank: The _______ is the movement of water through the atmosphere and over the surface of the Earth.
water cycle
Fill in the blank: The _______ is the movement of carbon compounds through the atmosphere, oceans, and living organisms.
carbon cycle
What processes are involved in the nitrogen cycle?
Nitrogen is converted into different forms as it cycles through the environment.
What drives the nitrogen cycle?
Microorganism fixation of atmospheric nitrogen and its conversion into a biologically useful form.
True or False: The carbon cycle involves the uptake of carbon via photosynthesis.
True
What are some examples of freshwater systems?
Small ponds, wetlands, large lakes, rivers.
What are some examples of terrestrial biomes?
Tropical rainforests, arctic tundra.
