KA Biology Unit 1 Notes

Unit 1: Ecology and natural systems

Organization of natural systems

There are two factors: Biotic and Abiotic

Biotic = Life

Tree, plants, humans, animals

A biotic factor is a living organism, such as a plant, animal, fungus, or bacterium. 

Biotic factors can also include how an organism interacts with any living part of its environment. 

For example, bacteria inside an animal’s intestines are biotic factors that help with food digestion. A herd of bison feeding on grasses in a prairie is also a biotic factor.

Abiotic = Non-Life/ Without life.

Example: water, soil, air

An abiotic factor is a non-living part of the environment, such as sunlight, temperature, precipitation, or humidity. Other abiotic factors include water and wind currents as well as nutrients and minerals in soil.

Antibiotics kill living things in your body. They are used to kill bad bacteria in your body, but can also have a negative effect, such as killing healthy gut bacteria.

Earth Level Systems:

These levels are described as spheres as Earth itself is a sphere. The four main levels are:

Atmosphere: the layer of gases that surrounds a planet and protects it from space. 

The atmosphere is all the gases that surround the Earth.

The atmo prefix refers to all the air around the earth. There is a 60 mile thick layer of atmosphere.

The Earth's atmosphere is made up of several gases, including:

Nitrogen: The most common gas in the atmosphere, nitrogen dilutes oxygen and prevents rapid burning. Living things also need nitrogen to make proteins.

Oxygen: Used by all living things for respiration and combustion.

Argon: Used in light bulbs, double-pane windows, and to preserve museum objects.

Biosphere: All the living organisms on the Earth

The biosphere is made up of all the living organisms on Earth. Living organisms can be found inside rocks deep underground to high in the atmosphere.

Hydrosphere All water on Earth including oceans, lakes, rain, icebergs, anything!

Geosphere:  is the interior and surface of the Earth, including rocks, continents, and the ocean floor.. Non-water and non-gas components of the earth like rocks, grass, etc.. 

The members of a specific species that share the same area are called a population

All members in a particular population are members of the same species. There can be other members of the species who aren’t in that same population.

A certain area doesn’t tend to have just one population

All the living things in a certain area are a community.  There is a biotic community and an abiotic environment. Those two make up an ecosystem

Ecosystem: a community of living organisms (biotic factors) interacting with their nonliving physical environment (abiotic factors) within a specific area.

A community is a group of different species that interact with one another within a specific area.

A population is a group of individuals from the same species, living in the same general area.

The biotic and abiotic components are linked together through nutrient cycles and energy flows.

Conservation of matter: Matter goes from one form to another. 

Flow of energy: Energy tends to go through an ecosystem as sunheat then gets transferred. 

Some ecosystems are in land or water (aquatic). There can be salt water ecosystems (marine) and freshwater ecosystems (smaller subset).

You can look at small parts of big places as their own ecosystems. For example, your hand can be an ecosystem. The bacteria and other microorganisms are interacting with the air, oil on your screen, and how they are interacting with dead and living skin cells.

Major types of land ecosystems are called biomes. There are many types of biomes in this world.

Biomes are regions defined by specific abiotic factors to which plants, animals, and other organisms are well-adapted.

To determine an ecosystem, you look at the temperature, moisture, climate, minerals there, and the terrain. There can still be a lot of variety though. There are many kinds of deserts in the world, but they are not all exactly the same. They have distinct differences.

Terrestrial biomes are land-based biomes and are defined by their climate (temperature and precipitation). 

Aquatic biomes are water-based biomes and are defined by their water depth and salinity (saltiness of water).

Some biomes can be very small. A microbiome is a group of microbes (such as bacteria) that naturally live on or within another organism.

Each biome contains multiple ecosystems. Ecosystems can exist at different scales and within one another. Some ecosystems are very small and only occur under specific environmental conditions. These small, natural systems are called micro ecosystems and include soil, ponds and puddles, decaying logs, and tree cavities.

Each ecosystem contains multiple communities made up of many populations

The distribution of life

Abiotic factors are nonliving parts of the environment. Collectively, abiotic factors affect where life can exist and the types of organisms found in different parts of the biosphere.

Abiotic factors such as temperature and precipitation vary in relation to latitude. Latitude describes how far north or south an area is from the equator. Latitude is measured in degrees, which ranges from 0 degrees at the equator, to 90 at the north and 90 at the south.

Temperatures decrease with latitude.  At low latitudes, the sun’s rays strike the Earth’s surface most directly. 

So, equatorial regions tend to be warmer. At high latitudes, the sun’s rays hit the Earth’s surface at an angle and are more spread out. So, polar regions tend to be cooler.

Precipitation also tends to decrease with latitude. Temperature affects the amount of water vapor that air can hold; warm air holds more water vapor than cold air. 

Because of that, equatorial regions have more rain than other regions as the air can hold more water.

The number of different species in an area is known as species richness.

Species richness tends to be highest at low latitudes near the equator. Here, the climate is relatively warm and humid year-round, making it a favorable environment for many species.

Contrast, the species richness tends to be lower near the poles, as the increasing latitude makes the climates cooler and varies more with the seasons, making it more difficult for species to survive.

Species richness usually declines in relation to latitude in both terrestrial (land-based) and aquatic (water-based) systems.

However, in oceans, water currents play a major role in the distribution and number of marine species. So, trends of marine species richness can vary for some types of organisms.

Various abiotic factors affect how life is distributed in terrestrial and aquatic environments.

In terrestrial environments, elevation, temperature, and precipitation are important abiotic factors. The interaction of these factors affects where terrestrial organisms are found.

Species richness becomes more complex in mountain ranges because of variation in precipitation. 

As air moves up and over a mountain range, the air cools and its water vapor condenses into rain or snow. So, one side of a mountain range tends to have more precipitation and the other side tends to be drier. (rain shadow effect)

This variation in habitats across a mountain range leads to different patterns of species richness.

In aquatic environments, water depth, temperature, sunlight, and dissolved oxygen are important abiotic factors. The interaction of these factors affects where aquatic organisms are found.

Both temperature and sunlight change with water depth. The farther into the ocean, the cooler the temperatures and sunlight decreases.

In general, species richness is higher in warmer, sunlit areas near the surface of the ocean.

However, species richness becomes more complex in oceans because of ocean currents. Ocean currents can change abiotic factors, such as temperature, by moving and mixing water. These currents create varied environmental conditions and result in different patterns of species richness.

Aquatic environments can be divided into freshwater and marine (saltwater) ecosystems

Freshwater ecosystems contain freshwater (which has a low salt concentration, usually 

(<1%) and include lakes, rivers, and wetlands. Water velocity (how fast water moves) and pH (a measure of acidity) are additional important abiotic factors in freshwater ecosystems.

Marine ecosystems contain saltwater and include oceans, coral reefs, and mangroves. Ocean currents, dissolved nutrients, and proximity to land are additional important abiotic factors in marine ecosystems.

An organism's niche

Abiotic factors for an organism’s range (geographic area where the organism can range).

If there is a mountain range covering a lake, a fish range is only that lake. If there is a goat on a mountain and all around them is water, their range is the mountain. 

Other abiotic factors include temperature, water, moisture, acidity of water, and more. Some animals can only live near the equator, for example.

There are also biotic factors such as access to food or predators.

An organism niche (where you will see an organism (and the environmental conditions where you will see the organism)

Tolerance is how much you can tolerate something.

And so in general, for a given type of organism, we can describe what conditions we are likely to find them in and describe it in terms of tolerance.

We can map this with a  graph, in optimal conditions there will be a lot of fish. At lower tolerance there will be little, and upper tolerance there will also be little. It’s like a bell curve graph:

When we think about abiotic factors like temperature, acidity, and moisture, this is known as a fundamental niche (represents the environmental conditions in which an organism could exist.)

Realized Niche (the specific range of environmental conditions and resources that a species actually occupies within an ecosystem)

Certain interactions (such as competition or predation) and resource availability can restrict an organism’s use of its environment. As a result, an organism may only use a portion of its fundamental niche. This is called the organism’s realized niche 

When people are talking about an organism’s niche, they are likely talking about a realized niche, as that is most accurate.

Some organisms only live in one concentrated area, (specialized species) while other organisms can live in a lot of environments (generalist species).

Population growth and carrying capacity

A population is a group of individuals from the same species, living in the same general area.

We can describe a population using density. A population’s density refers to the number of individuals within a specific area.

A population can also show different types of dispersion, which describes how individuals are spread throughout their habitat.

• Clumped dispersion occurs when many individuals are packed closely together into groups, such as a school of fish when avoiding a predator. - 

• Uniform dispersion occurs when individuals are spaced evenly from one another (distance between them is the same (uniform), such as animals, like penguins or certain lizards, defending their territories around their burrows or nesting sites.

• Random dispersion occurs when individuals have an unpredictable distribution throughout their habitat. Individuals from plant populations with wind-dispersed seeds (such as dandelions and cottonwood trees) are often randomly spaced from one another.

Another way to describe population is the growth of a population. If the birth rate is larger than the death rate, the population is going to grow. If the death rate is higher than the birth rate, the population will decrease. 

There is also another factor, immigration and migration (leaving and coming in), which also influences population growth.

Populations have different growth patterns depending on environmental conditions (abiotic factors) and interactions within and among species (biotic factors).

Exponential growth occurs when a population grows exponentially; the larger the population becomes, the faster it grows. Exponential growth usually happens under optimal environmental conditions with plentiful resources. Populations that have exponential growth produce a J-shaped curve.

Logistic growth occurs when a population grows exponentially at first, but then slows. As the population’s growth slows, its size begins to level off. 

Logistic growth usually occurs as resources become scarce and competition increases. Populations that have logistic growth produce an S-shaped curve.

Exponential and logistic growth are mathematical models that are useful for describing how populations change over time. However, like all models, they have limitations. For one, populations cannot have indefinite exponential growth because resources are limited in natural systems (resources are finite).

In addition, population models only describe a populations’ growth over a specific period of time. For example, a population model can be used to show how a population has changed over the last 5 years or the last 500 years. Depending on the time period used, the model of a population’s growth can look very different!

Overall, it's important to remember that populations are dynamic. Populations can shift between different growth patterns over time, and they often show periods of growth, stability, and decline.

In general, species with r-selected traits have a short lifespan (short lived), usually smaller sized, and produce many (a lot of) offspring that require little to no parental care. 

Examples of species with r-selected traits include jellyfish, insects, rodents (such as rats and mice), and frogs.

In general, species with K-selected traits are long-lived (live for a long time) and tend to produce fewer (not many) offspring. These offspring require increased parental care. 

Examples of species with K-selected traits include many large mammals, such as elephants, horses, and primates.

However, no species is completely an r-selected or a K-selected species. Some species have a mix of traits, while other species may have more r-selected traits or more K-selected traits.

Species that have more r-selected traits often occur in environments with variable (prone to change) or unstable conditions. When conditions are favorable, populations of these r-selected species may respond quickly and show exponential growth over a short period of time.

Although populations of r-selected species can grow rapidly, this growth is often temporary. r-selected species may overshoot their environment’s carrying capacity and then quickly decline as environmental conditions change, resulting in “boom-bust” population dynamics as seen in the graph belowL

Species that have more K-selected traits are often found in environments with relatively stable conditions. When conditions are consistent, populations of these K-selected species may grow slowly and show logistic growth over an extended period of time.

The growth K-selected traits undergo is sustained, as they stabilize near their environment’s carrying capacity. So, K-selected species may maintain a stable population size as long as environmental conditions remain steady, as seen in the graph below.

However, it's important to realize that r- and K-selected species can both show periods of exponential or logistic growth in their populations. The specific growth patterns shown will depend on environmental conditions, resource availability, and limiting factors.

Activity: Why are human-shark interactions increasing around Cape Cod?

The increase in human-shark interactions around Cape Cod is primarily due to a combination of factors, with the most significant being the resurgence of the gray seal population. Here's a breakdown:

• Increased Seal Population: Gray seals are the primary food source for great white sharks in this area. Conservation efforts have led to a significant rebound in the seal population around Cape Cod, creating an abundant food source that attracts sharks to the nearshore waters.

• Shark Presence: With more seals present, great white sharks are spending more time closer to the shore, where humans also frequent for recreational activities like swimming, surfing, and kayaking. This overlap in habitat increases the likelihood of encounters.

• Mistaken Identity: While sharks don't intentionally target humans, there's a possibility of mistaken identity. When viewed from below, a surfer on a board or a swimmer might resemble a seal, potentially triggering a predatory response from a shark.

• Increased Human Activity: Cape Cod is a popular tourist destination, especially during the summer months. The increased number of people using the beaches and waters naturally leads to a higher chance of encountering a shark.

Interactions in communities

Every ecosystem contains communities of interacting organisms. Interactions may help, harm, or have little to no effect on the individuals involved. 

Interactions in communities are: competition, predation (and herbivory). 

Symbioses are: (mutualism, commensalism, and parasitism).

Competition occurs when individuals (from the same or different species) compete directly or indirectly for the same limited resources. Competition negatively affects all individuals (Both organisms are negatively affected) involved and may harm their survival and/or reproduction.

Predation involves one organism (the predator) that kills and eats another organism (the prey). 

Predator and prey populations often cycle through time in relation to changes in climate and resource abundance. 

As the prey population increases, the predator population often increases as well. However, as the prey population grows, predation pressure and increased competition for resources may cause the prey population to decline. In turn, the predator population may decline as well. See a graph below:

Predators may feed on a variety of species or they may prey exclusively on one species. Many predators are also scavengers and consume the remains of dead organisms.

Similar to predation, herbivory occurs when a non-plant species feeds on a plant species. Herbivory can involve the consumption of all or part of a plant. So, unlike predation, herbivory does not always result in the death of an individual. 

Symbioses are close, long-term associations between two or more species. Here are the types of symbiosis:

Mutualism occurs when all species involved benefit from a symbiotic association. (Both are benefited)

• Some species participate in facultative mutualism, whereby they benefit from a symbiotic association with another species but are not dependent on it.

• Other species are involved in obligate mutualism, which means their survival is dependent on their symbiotic association with another species.

Commensalism occurs when one species benefits from a symbiotic association while the other is neither harmed nor helped. (One is benefited, one is unaffected)

Parasitism occurs when a species (the parasite) lives in or on another species (the host). 

The parasite obtains its nutrition by feeding on the host’s tissues or fluids, and the host is harmed in the process. Endoparasites are found within a host and ectoparasites occur on the host’s body. (One is harmed, one benefits)

A community is made up of many interacting species. Interactions can occur between individuals of the same species or different species.

• When interactions occur between individuals of the same species, they are called intraspecific interactions.

• When interactions occur between individuals of different species, they are called interspecific interactions.

Interactions within and among species affect community structure (the composition of a community, including the number of different species present, their relative abundance within that community, and how those species interact with each other within a given environment;)

Competition is one of the most important interactions that regulates (or controls) populations in a community. 

Competition occurs when individuals compete directly or indirectly for the same limited resources, such as food, space, or mates. Competition can be intraspecific or interspecific.

Individuals of the same species share the same niche. In turn, they compete for the same resources. This is known as intraspecific competition.

Intraspecific competition tends to increase with population density. This is because at high population densities there are more individuals competing for the same amount of limited resources. 

So, an increase in intraspecific competition can slow population growth.

Individuals of different species do not share the exact same niche—but they may compete for some of the same resources. This is known as interspecific competition.

Interspecific competition can influence the geographic distribution and range of species. One species can exclude another species from an area by successfully competing for similar resources, such as prey or nesting sites.

A species may compress or shift its niche when interspecific competition restricts its use of resources. In contrast, if there is little or no competition, a species may expand its niche.

Environmental variation can allow competing species to coexist. In some cases, one species will have a temporary advantage over another. However, once environmental conditions change, the advantage may shift to another species.

Different species have different niches, which allows them to share resources in a community and avoid competition. This is called resource partitioning (also called niche partitioning). 

Resource partitioning involves species using different resources, occupying different areas of a habitat, or feeding during different times of the day.

The competitive exclusion principle states that different species cannot coexist in a community if they compete for all of the same resources. 

According to this principle, if two species use the same resources but one has an advantage over the other, the species with the advantage will outcompete and dominate the other. Over time, this can lead to the decline or extinction of the disadvantaged species.