Topic 12 Notes

Characteristics of Life & Biotic vs. Abiotic

BIOLOGY is the study of LIFE!

What are the Characteristics of Living Things?

Living things are made up of cells.

Living things reproduce.

Living things contain some type of genetic code/genetic information (DNA, RNA).

Living things grow and develop.

Living things obtain and use energy.

Living things respond to their environment/stimuli.

Living Things can evolve.

Living things maintain homeostasis (stable internal environment).

Characteristics of Life Video

Living Things are Made up of Cells...

Cells: collection of living matter enclosed by a barrier that separates the cell from its surroundings; basic unit of all forms of life

Cells can grow, respond to their surroundings, and reproduce. Despite their small size, cells are complex and highly organized. We'll be learning a lot more about cells this year!

Unicellular Organisms: living things made up of ONE cell

Multicellular Organisms: living things made of many cells

Living Things Reproduce...

There are two basic types of reproduction:

Sexual Reproduction: two cells from different parents unite to produce the first cells of a new organism

Asexual Reproduction: the new organism comes from a single parent

Living Things Contain a Genetic Code/Genetic Information...

The inheriting of traits is due to a molecule known as deoxyribonucleic acid aka DNA. With a few exceptions, DNA is the genetic code that determines the inherited traits of an organism We will learn more about DNA structure and genetic inheritance this year!

Living Things Grow and Develop

Every organism has a life cycle, a pattern of growth and change that occurs over and organism's life. All organisms grow during their lifetime. The life cycle of many types of multicellular organisms also involves a process called development. During this process, the cells in an organism not only increase in number but also differentiate (become different).

Living Things Obtains and Use Energy

Metabolism: set of chemical reactions through which an organism builds up or breaks down materials as it carries out its life processes.

Organisms require energy in order to grow, develop, and reproduce.

Living Things Respond to Their Environment

Organisms live in constantly changing environments. A living thing must find ways to respond to stimuli and other changes.

Stimuli: A “cue” or trigger that causes something to happen (causes a reaction)

Example of Homeostasis : Maintaining body temperature

Living Things Can Evolve

Evolve: change over time

Over a few generations the changes in a group may not seem significant. But over hundreds, thousands, or even millions of years the changes can be dramatic. Living things must be able to change over time aka evolve in order to survive in an ever changing world.

Living Things Maintain Homeostasis

Homeostasis: the process by which organisms keep their internal conditions stable and balanced

If homeostasis is changed in a major way, an organism may not survive.

homeostasis = internal balance

The body must maintain a stable internal environment. Not too high, not too low, but just right.

THINK ABOUT IT!

Explain how the story of Goldilocks and the Three Bears relates to homeostasis.

EXAMPLE: A mnemonic to help remember the 8 characteristics of life.

"(Valley) grads drive really energy-efficient hybrid cars responsibly."

GROWS and develop - (Valley) GRADS

DNA (RNA) - DRIVE

REPRODUCES - REALLY

ENERGY (obtain & use) - ENERGY

EVOLVES- EFFICIENT

maintains HOMEOSTASIS- HYBRID

be made of CELLS- CARS

RESPONDS to the environment - RESPONSIBLY

Ecological Relationships

CLICK HERE to watch a video about Ecological Relationships!

Vocabulary

Symbiosis: any type of close and long-term biological interaction between two different biological organisms
Mutualism: the ecological interaction between two or more species where each species has a net benefit.
Commensalism: a relationship between individuals of two species in which one species obtains benefits from the other without either harming or benefiting the latter.
Parasitism: a relationship between two species of plants or animals in which one benefits at the expense of the other, sometimes without killing the host organism
Predation: one organism kills and consumes another. Predation provides energy to prolong the life and promote the reproduction of the organism that does the killing, the predator, to the detriment of the organism being consumed, the prey.
- Predator/Prey Dynamics:

Predators affect the population size of their prey, but as the number of prey decreases so does the number of predators. The relationship is called a predator-prey cycle, and it shows how each regulates the population of the other in a natural setting. Problems can occur when populations are not controlled. This may be due to introducing a new species that has no natural predators. Some populations may also die off due to a lack of resources. Understanding population growth is important as each population impacts others within an ecosystem.

Food Chains & Food Webs

Sunlight is the main energy source for life on earth. Energy flows through an ecosystem in one direction, from the sun or inorganic compounds to autotrophs/producers and then to various heterotrophs/consumers. The relationships between these autotrophs and heterotrophs can be organized into food chains and food webs. Both food chains and food webs show how energy flows from the different organisms by showing who eats who.

Each level in a food chain or food web is called a trophic level.

Food Chain: series of steps in an ecosystem in which organisms transfer energy by eating and being eaten. A food chain shows how energy is passed from a producer (an organism that makes its own food) to consumers (organisms that eat other organisms for food) in an ecosystem.

Below is an example of a food chain...

This food chain tells us that when sea urchins eat kelp, the energy from the kelp is transferred to the sea urchin. When sea otters eat sea urchins, the energy from the sea urchin is transferred to the sea otter. And, when bald eagles eat baby sea otters, the energy from the otters is transferred into the bald eagle.

The bald eagle is the apex predator of the food chain. He has no predators. His energy will be passed to scavengers (animals that feed on dead animals) and decomposers (organisms that break apart dead organic matter) when he dies.

When making a food chain be sure to always start with the producer!

(Producers could be algae, kelp, or phytoplankton.)

DON’T FORGET! THE ARROWS IN A FOOD CHAIN/WEB POINT IN THE DIRECTION THAT ENERGY IS MOVING!!

Food Webs are very similar to food chains however they show a series or network of interactions between organisms. In other words, in a food web, you can see all the different ways energy can be transferred, whereas a food chain only shows one linear way energy is transferred between organisms.

A food web has many connections among its producers, consumers, and decomposers. It displays these relationships in an intricate web. A food chain, on the other hand, only shows one set of relationships from a producer to a primary consumer to a secondary consumer. A food web is, therefore, more accurate and more stable than a food chain because it will handle changes in the community much easier.

Additional Vocabulary

A producer is an autotroph. An autotroph makes its own food using photosynthesis or chemosynthesis, processes that use energy to convert inorganic carbon (CO2) to organic carbon (glucose). The producer in the food chain above is the kelp!
Consumers are heterotrophs and must eat food for energy. This food can be a producer, another consumer, or a mixture of both. The consumers in the food chain above are the sea urchin, otter, and bald eagle.
Consumers can be:

- herbivores, which only eat plants and/ or algae.

- carnivores, which only eat animals or zooplankton.

- Scavengers are a type of carnivore that eat only dead animals (carrion).

- omnivores, which eat plants or algae and animals or zooplankton.

In the food chain above Bald eagles and sea otters are CARNIVORES which means they only eat other animals. The sea urchins are OMNIVORES and only eat algae such as kelp.

The primary consumer eats the producer in a food chain. The primary consumer in the example above is the sea urchin.
The secondary consumer eats the primary consumer in the food chain. The secondary consumer in the example above is the otter.
The tertiary consumer eats the secondary consumer in the food chain. The tertiary consumer in the example above is the eagle.
Decomposers are bacteria and fungi that break apart dead organisms into simpler chemicals. Decomposers would take energy from every level of the food chain as they are able to use any dead organism as a source of energy.

Ecological Pyramids

Energy Pyramid:

a diagram that shows the transfer of energy from one level of feeding to another

Each step of the energy pyramid is called a trophic level.

It is made up of organisms that have the same function in the food chain.

The “loss” of energy at each level of the food chain can be represented by an energy pyramid!

Kelp is a producer. It converts the sun’s energy to food using photosynthesis. The same molecule that is produced for food, glucose, can also be used to make other compounds like proteins, fats, and nucleotides that make up the mass of the kelp.

When the sea urchin (a primary consumer) eats kelp, approximately 10% of the energy from the kelp will go to building new mass for the urchin. The remaining 90% will be used for metabolic processes and will be lost as heat.

When the sea otter (secondary consumer) eats the sea urchin, approximately 10% of the energy from the sea urchin will go to building new mass for the sea otter. The remaining 90% will be used for metabolic processes and will be lost as heat. This means that 1% of the energy from the kelp is used.

By the time an eagle (tertiary consumer) eats a sea otter pup, only 0.1% of the energy that was in the kelp is left in the system.

For this reason, an ecosystem must have high populations of producers and primary consumers to support smaller populations of secondary and tertiary consumers.

Energy Flow:

As energy flows through an ecosystem only 10% of energy available in one trophic level is passed to the next. 90% of it is lost as heat.

When an organism eats food it does not gain all the mass of the food.

For example if a zebra eats 10kg of grass it does not increase in mass by 10kg. This is because a lot of the energy stored in the grass is lost. As the zebra eats the grass it uses some of the energy to run and to grow. Some is stored as fat and muscle in the zebra’s body. Some is lost as heat.

From producer to consumer the amount of energy within each trophic level decreases.

Types of Ecological Pyramids

Trophic levels in an ecosystem can be described as pyramids. Primary producers are on the bottom & consumers on top.

Missed Class or need to review? Watch THIS video!

Energy pyramids: show the amount of energy available at each trophic level. Their shape is always wide at the bottom and narrow at the top.

Pyramid of Numbers: A pyramid of numbers shows how many individuals are needed to support the food chain.
- For example, a small pod of ten killer whales can get enough calories for a day from one gray whale calf. The gray whale calf consumes around 2% of its body weight in amphipods each day, around 340,000 organisms. (An amphipod is a shrimp-like organism that lives in tubes on the ocean floor.) Amphipods, in turn, consume diatoms and other phytoplankton.

Pyramid of Biomass: depict the dry weight of all the organisms at each tier.
- For terrestrial ecosystems, the base is wide and narrows to the top. For marine ones it’s inverted because phytoplankton grows and reproduce so fast, they can support vast biomass. For example, in this food chain, because diatoms (phytoplankton) are so small even millions of organisms would have a small mass compared to even 1 killer whale.

Niche: Fundamental vs Realized Niche

What is a niche?

A niche describes where an organism lives and what it does "for a living" including the way it interacts with biotic and abiotic factors. A species niche includes the range of physical and biological conditions in which it can survive and reproduce, as well as the way it obtains the resources it needs.

This is the role an organism plays in its habitat, not just where it lives, but how it functions in that community. Many similar species may share a habitat but no two species can occupy the same niche. When niches overlap competition will result. For example, rabbits and a deer may compete because they both are herbivores.

Ecological Sucession

All ecosystems change over time. As they change the type of organisms that live there also changes. Often one community is replaced by another and this is known as succession. The way a community comes into being after a catastrophic event is called ecological succession.

Primary succession happens when there is a complete wipeout of life needing to start over (like a volcano erupting)

Secondary succession is when there is damage done but some organisms (like plants) are left behind (like a forest fire).

- As soil forms from the decomposition of earlier plants, small plants can grow. They die and their organic matter enriches the soil for larger plants to grow. Eventually, larger and larger species can inhabit that area.
- Trees and shrubs colonize next and outcompete and replace the grasses, eventually leading to a stable forest community made up of oaks and maples. This is called a climax community. At this point equilibrium in the ecosystem is restored.

Ecosystems are sometimes destroyed by natural catastrophes such as volcanoes, earthquakes, fires, floods. If this leaves behind barren land the process that follows is known as PRIMARY SUCESSION.

- It begins in a barren area (volcanic island, glacier retreat) where a pioneer species colonizes the region. After the volcano erupts, the surrounding land is barren, lifeless and rocky. The first organisms to colonize the area are called pioneer species. These are usually small fast growing plants that reproduce quickly and disperse well.
- The pioneer organisms include lichens and mosses, which help form the soil layer so that other species may also live there. They can break down the minerals in rocks to begin to form soil.

Succession also occurs when a tree falls down in a forest or in areas that have natural rainy and drought cycles. During the rains one type of grass may dominate, but during the drought other types may dominate. This type of succession is known as SECONDARY SUCCESSION.

Secondary succession occurs in a disturbed area where the soil is already in place (e.g. after a forest fire or drought).

Invasive Species:

Organisms that are brought to a new environment that does not originally belong there and displaces the native species. Invasive species usually reproduce quickly and have no natural predators so they eat all of the food of the native species (increase competition!) and the native species die.

CLICK HERE to read an article about invasive species impacting the Aleutian Islands!

Population Growth

Under ideal conditions with unlimited resources, a population will increase exponentially...

Exponential Growth: When the availability of resources is unlimited in the habitat, the population of an organism living in the habitat grows in an exponential fashion aka increases rapidly with no signs of stopping

Carrying Capacity: the maximum number of individuals of a particular species that an environment can support.

Logistic Growth: (s-shaped growth curve) Occurs when a population's growth slows and then stops following a period of exponential growth.

Competition

COMPETITION: an interaction between organisms or species in which both the organisms or species are harmed. A limited supply of at least one resource used by both can be a factor, this is known as a limiting factor...

LIMITING FACTORS are resources or environmental conditions that limit growth, abundance, or the distribution of an organism or population.

Density Dependent Limiting Factors

vs.

Density Independent Limiting Factors

Remember This!

Competition is an example of a density-dependent limiting factor!

This is because competition can LIMIT how much a population can increase!

Cycles of Nature

Organisms in an ecosystem require energy, hydrogen, carbon, oxygen, nitrogen and phosphorous.

There are cycles for each of these which describe how nutrients are shuffled between an environment and its organisms!

The Water Cycle

The Hydrologic Cycle aka the Water cycle is the movement of water from its main reservoir (ocean) to the atmosphere (evaporation from bodies of water and transpiration from plants), forming clouds (condensation) and back down to the soil or ocean (precipitation) and back into the ocean (runoff).

Evaporation: the process of a substance in a liquid state changing to a gaseous state due to an increase in temperature and/or pressure.
Condensation: the process in which water in its gas form condenses to form liquid water; it is the opposite of evaporation
Precipitation: any liquid or frozen water that forms in the atmosphere and falls back to the Earth. Along with evaporation and condensation, precipitation is one of the three major parts of the global water cycle. Precipitation forms in the clouds when water vapor condenses into bigger and bigger droplets of water.
Transpiration: The evaporation of water from plants. It occurs chiefly at the leaves while their stomata (think plant pores) are open for the passage of CO2 and O2 during photosynthesis.
Run-Off: water from rain, snow, or other sources that flows over the land surface

Still confused?

Check out this video about the water cycle!

The Carbon Cycle

Most carbon is in the deep ocean and sediments (soil) and is slowly cycled. The rest is cycled more quickly between shallow ocean, atmosphere, soil and living things.
Plants take in CO2 from the atmosphere and turn it into glucose and other products.
Animals take in the glucose and break it down and release CO2.
Animals and plants die, decomposers return their carbon to the soil.
Carbon in sediments (soil) can be burned as fossil fuels. Driving cars, burning of trees and forests, burning of coal will release the CO2 into the atmosphere.

Carbon Sinks/Reservoirs

"A carbon sink is anything that absorbs more carbon from the atmosphere than it releases – for example, plants, the ocean and soil. In contrast, a carbon source is anything that releases more carbon into the atmosphere than it absorbs – for example, the burning of fossil fuels or volcanic eruptions."

"The ocean, atmosphere, soil and forests are the world’s largest carbon sinks. Protecting these vital ecosystems is essential for tackling climate change and keeping our climate stable."

Source: ClientEarth

The Nitrogen Cycle

Nitrogen is necessary for bacteria, plants, and animals. Plants and animals both obtain their nitrogen after it has been fixed by bacteria. Most nitrogen is in the form of N2 (atmospheric) which very few organisms can use, therefore nitrogen tends to get transformed into other usable forms by things like bacteria.

There are 5 basic mechanisms for cycling nitrogen:

Nitrogen fixation—some bacteria convert N2 to ammonia (NH3). This form can be used by other organisms.
Decomposition and Ammonification—decomposers use the proteins from dead organisms. They turn the nitrogen into NH3 (ammonia) and NH4+ which plants can use.
Nitrification—other bacteria act on NH3 and NH4+ resulting in NO2- (nitrite) that is further converted to NO3- (nitrate) that plants can use.
Denitrification—other bacteria can take NO3- in soil and turn it into N2 which is released as a gas into the atmosphere.
Assimilation: the process by which plants and animals incorporate the NO3- (nitrates) and ammonia formed through nitrogen fixation and nitrification. Plants take up these forms of nitrogen through their roots and incorporate them into plant proteins and nucleic acids.

Still confused?

Check out this video about the carbon and nitrogen cycles!

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