Read about symbiosis. Then answer the questions provided.

Question

Symbiosis

Identify the type of symbiosis described.

The saguaro cactus provides food for the white-winged dove through its large fruit. The bird consumes the fruit, ingests the seeds, and then deposits the seeds in a new location. Many times organisms live together for beneficial reasons. This relationship may benefit one of the partners, or both of them, and they usually interact with each other for long periods of time. Whatever the interaction, when two organisms of different species have a relationship, it is called symbiosis. Living and working together helps organisms to survive in their environments.

There are three main types of symbioses: mutualism, in which both organisms in the relationship benefit, commensalism, in which one organism benefits and the other is unharmed, and parasitism, where one benefits and the other is harmed.

Mutualism – Everybody Wins!
Inside the human gut are many species of bacteria that live nowhere else. These bacteria are responsible for helping in the digestion of the food people eat. In exchange, the bacteria get nutrients they need to survive. This type of relationship is called mutualism. Here, both species involved with the interaction benefit. In this case, humans get help digesting food and the bacteria get energy from the food they help to digest. Another example of mutualism is shown between the white-winged dove (Zenaida asiatica) and the saguaro cactus. Here, the dove eats the fruit of the cactus, seeds and all. The seeds are then deposited in other locations as the bird moves. The birds get food and the cactus gets help with dispersal of its seeds.

A dove sitting on a cacti eating it's fruit.
The white-winged dove eats the fruit of the saguaro cactus. It eats gets food from the fruits and then transports the digested seeds to new locations.
Commensalism – I Win! You Just Are!
In commensalism, one organism benefits, while the other is unharmed. Orchids are flowers that live in the tropical rainforest. Since light and other resources are limited there, these flowers often grow attached to the branches of trees. The orchids grow towards the light and collect nutrients as they run down the trunks of the trees. The orchids do not grow so large as to block out light or other resources for the tree; therefore, no harm is done to it.

The remora and shark form another example of commensalism. Remoras, also called pilot fish, usually swim alongside sharks, collecting leftover food particles in the water. The sharks do not pay any attention to the remoras, thereby leaving them unharmed.

A shark in the ocean with remoras attached to it.
The remora follows the shark around to collect leftover food scraps. The shark is unaffected by this behavior.
Parasitism – I Win! You Lose!
Parasitism results in one organism benefiting at the expense of another. It is important to note that parasites will not usually kill their hosts, only damage them. This is because if a parasite kills its host, it loses its main source of nutrition.

Aphids are the juvenile forms of many insects that survive by sucking the sap out of the plants on which they live. This feeds the aphids but damages the plants because needed nutrients are lost from the sap. The brown-headed cowbird (Molothrus aterI) is a nest parasite, meaning it lays its eggs in the nests of other birds. To make room, the cowbird will kick out the nest bird’s eggs. The nest bird parents will raise the cowbird young as their own, often at the expense of their own young. Additionally, the cowbird young normally hatch first. It will push the other eggs out of the next to make sure it receives all of the nest bird’s attention.

A bird's nest with 2 similar looking eggs and 1 egg that is speckled.
The spotted cowbird egg in this nest was placed here so the parents of the other eggs could care for it. The cowbird removed one of the other bird’s eggs to make room for its own.
Living things depend upon each other in several different ways. Which of these symbiotic relationships is the best? Why do you think so?

Answer 1

In the provided example of the saguaro cactus and the white-winged dove, the type of symbiosis described is mutualism. In this relationship, both the cactus and the dove benefit: the dove gets food from the cactus’s fruit, while the cactus benefits from the dove's assistance in seed dispersal. The interaction helps both species survive and thrive in their environments.

As for which type of symbiotic relationship is the best, many might argue that mutualism is the most beneficial overall. This is because it promotes cooperation and support between species, enabling both organisms to thrive. In mutualistic relationships, both parties actively contribute to each other’s well-being, creating a balanced interaction that can help sustain ecosystems. For example, the relationship between bacteria in the human gut and humans themselves is crucial for digestion and overall health, showing how mutualism can enhance the survival and well-being of both partners.

Commensalism may be less impactful since it involves one organism benefiting without harming the other, but it doesn't provide the same level of interaction and support found in mutualism. Parasitism, while it allows one organism to benefit, often comes at a significant cost to another, leading to an imbalance that can ultimately harm ecosystems.

In summary, mutualism is likely considered the best type of symbiotic relationship due to the positive effects and benefits it confers to both organisms involved.

Answer 2

Identify the type of symbiosis described.

The brown-headed cowbirds lay eggs in other birds’ nests. They trick the birds into raising their young. The cowbirds hatch first and push the eggs out of the nest. The cowbirds are then fed by the nest-builder.

Answer 3

The type of symbiosis described in this scenario is parasitism. In this relationship, the brown-headed cowbirds benefit by having their young raised at the expense of other birds, which are harmed because the cowbirds push their eggs out of the nest and take the resources (such as food and care) that would have been invested in the nest-builder's own chicks. This interaction harms the host birds while allowing the cowbirds to thrive.

Answer 4

Read about invasive species. Then answer the questions provided.

Wild Parsnip

Describe the invasion of wild parsnip, including the harm it causes.

Nature is being invaded by aliens! Well, not exactly aliens, but organisms that come from other places. These species, called invasive species, are those that get transported from one area to another accidentally by humans. These invaders are usually much better competitors than native species and, as such, outcompete the natives for resources. For example, the wild parsnip (Pastinaca sativa) is a dangerous plant that has come to North America from Europe and Asia. It was originally brought here by European settlers to be used as an edible root. It has since broken free of the garden and been growing quite successfully in the wild.

Flowering wild parsnip.
Wild parsnip is an invasive species from Europe and Asia that inhabits open fields and lawns.
What is Wild Parsnip?
Wild parsnip is a non-woody, green plant that is a member of the carrot family. It typically lives in areas that have been disturbed, but can also grow in fields, lawns, and even on the side of the road. The plant can grow up to 5 feet tall and often has yellow-green leaves and yellow flowers. The flowers are clustered together in a cap that is between 3 and 8 inches across. Flowering happens during the plant’s second year, producing seeds that are flat and brown. The seeds are spread by the wind in the fall.

Wild parsnip gone to seed.
The seeds of the wild parsnip plant are flat and brown. They form at the top of the plant so they can be picked up by the wind for dispersal.
Dangers of Wild Parsnip
Wild parsnip poses a danger to humans. It contains chemicals called furocoumarins that can irritate the skin. These chemicals make the skin more susceptible to ultraviolet (UV) light, which comes directly from the sun. As a result, coming in contact with the chemicals of the plant can lead to severe burns on the skin within a short period of time and can discolor the skin for years.

The best way to protect against wild parsnip burns includes learning to identify the plant to avoid exposure and wearing gloves and other protective clothing when working outside. If contact happens, wash the area with soap and water and keep the area covered for at least 48 hours to try to prevent the reaction with UV light.

Managing Wild Parsnip
Since wild parsnip is so dangerous to humans, it is advised to remove it from areas where people or pets may be. The easiest way to remove it is to pull it out of the ground by hand. This should be done before the plants start to make seeds. Be sure to wear protective clothing when doing this. Also, immediately wash any clothing and tools used so that the oils will not be spread to other places. If there are already seeds on the plants, cut off the parts that have the seeds and place them into a bag and dry them in the sun for a week to kill them. Chemical treatments can also work for larger areas. Spraying herbicides directly onto the roots and using mechanical brush cutters also work for clearing large areas of the plants. By killing the plants right down to the roots, additional growth can be prevented.

Answer 5

The invasion of wild parsnip (Pastinaca sativa) is a significant ecological issue in North America, where this invasive species has spread from its native regions in Europe and Asia. Initially introduced by European settlers for its edible roots, wild parsnip has escaped cultivation and now thrives in various disturbed environments, including fields, lawns, and roadside areas.

Description of the Invasion

Wild parsnip is a non-woody green plant belonging to the carrot family, capable of reaching heights of up to 5 feet. It is characterized by its yellow-green leaves and clusters of yellow flowers that bloom during its second year of growth. The plant produces flat, brown seeds that are dispersed by the wind in the fall, contributing to its spread and establishment in new areas. Its ability to outcompete native flora for resources has made it a dominant species in many habitats.

Harm Caused by Wild Parsnip

The presence of wild parsnip poses various dangers, particularly to human health. The plant contains chemicals known as furocoumarins, which can irritate the skin and increase vulnerability to ultraviolet (UV) light. Contact with the plant can lead to severe burns and long-lasting skin discoloration. Such interactions highlight the need for awareness and protective measures when in areas where wild parsnip grows.

Management Strategies

To mitigate the risks associated with wild parsnip, it is advised to remove the plant from locations frequented by people and pets. Effective removal methods include:

• Hand Pulling: This is most successful when done before the plant produces seeds. Protective clothing should be worn during the process, and any tools used should be washed immediately afterward to prevent the spread of oils from the plant.
• Cutting: If the plants have already produced seeds, cutting off the seed heads and bagging them for drying can help prevent further dispersal.
• Chemical Treatments: For larger infestations, applying herbicides directly to the roots or using mechanical brush cutters can also be effective in controlling wild parsnip populations. These methods aim to eliminate the plants down to the roots to prevent regrowth.

In summary, the invasion of wild parsnip in North America presents both an ecological challenge and a human health hazard. Effective management and public awareness are crucial to addressing the threats posed by this invasive species.