Biology 1 Flashcards
Plant parasites can be broadly categorized into several types based on their mode of parasitism and interaction with host plants:
Root Parasites: These parasites attach to the roots of host plants and derive nutrients from them. Examples include dodder (Cuscuta spp.) and witchweed (Striga spp.).
Stem Parasites: Stem parasites attach themselves to the stems of host plants and extract nutrients. Mistletoe is a common example of a stem parasite.
Leaf Parasites: Leaf parasites directly attack the leaves of host plants, often causing damage and reducing photosynthetic capacity. Examples include parasitic fungi like rusts and mildews.
Hemiparasites: Hemiparasitic plants are capable of photosynthesis but also rely partially on host plants for water, minerals, and nutrients. They may attach to the roots, stems, or leaves of host plants. Examples include broomrape (Orobanche spp.) and Indian paintbrush (Castilleja spp.).
Holoparasites: Holoparasites are entirely dependent on host plants for their nutrients and lack chlorophyll, so they cannot photosynthesize. They typically attach to the roots of host plants. Examples include ghost pipe (Monotropa spp.) and toothwort (Lathraea spp.).
Root Parasites:
These parasites attach to the roots of host plants and derive nutrients from them. Examples include dodder (Cuscuta spp.) and witchweed (Striga spp.).
Stem Parasites
Stem parasites attach themselves to the stems of host plants and extract nutrients. Mistletoe is a common example of a stem parasite.
Leaf Parasites:
Leaf parasites directly attack the leaves of host plants, often causing damage and reducing photosynthetic capacity. Examples include parasitic fungi like rusts and mildews.
Hemiparasites:
Hemiparasitic plants are capable of photosynthesis but also rely partially on host plants for water, minerals, and nutrients. They may attach to the roots, stems, or leaves of host plants. Examples include broomrape (Orobanche spp.) and Indian paintbrush (Castilleja spp.).
Holoparasites:
Holoparasites are entirely dependent on host plants for their nutrients and lack chlorophyll, so they cannot photosynthesize. They typically attach to the roots of host plants. Examples include ghost pipe (Monotropa spp.) and toothwort (Lathraea spp.).
Examples of root parasites
Examples include dodder (Cuscuta spp.) and witchweed (Striga spp.).
Examples of stem parasites
Mistletoe is a common example of a stem parasite.
Examples of Leaf Parasites
Examples include parasitic fungi like rusts and mildews.
Examples of Hemiparasites
Examples include broomrape (Orobanche spp.) and Indian paintbrush (Castilleja spp.).
Examples of holoparasites
Examples include ghost pipe (Monotropa spp.) and toothwort (Lathraea spp.).
Parasitic
plants attach and feed off other
plants using a parasitic structure
called a
haustorium.
haustorium.
The haustorium
is a specialised multicellular organ
homologous to a root, which penetrates
a host, makes a vascular connection,
and facilitates the transfer of nutrients
and other molecules.
division of parasytic plants
Parasitic
plants can be divided based on whether
they are photosynthetically active
(hemiparasites) or lack photosynthetic
activity and rely entirely on a host for
carbon (holoparasites), whether they
are facultative or obligate parasites, and
whether they attach to the host’s roots
or stem.
What do they parasitise?
Parasitic
plants vary in their host dependence
and the range of hosts to which they
can attach. Facultative hemiparasites
can complete their lifecycle without a
host, while obligate parasites (which
can be hemi- or holoparasites) need a
host to survive and reproduce. Many
facultative parasites are generalists
that can attack a broad range of hosts;
for example, Rhinanthus can attach to
more than fi fty species of herbaceous
plants and grasses. Obligate parasites
(particularly holoparasites) are more
likely to be specialised on a single host
plant species or a narrow host range,
and host-shifts can be involved in
speciation.
What is the lifecycle of a parasitic
plant?
Parasitic plants must
synchronise their lifecycle with their
host to maximise fi tness. The tiny seeds
of obligate root parasites like Striga only
germinate after a conditioning period
of suitable temperature, followed by
exposure to host-derived chemical
signals, such as strigalactones, which
are extruded by the host’s roots
to signal to symbiotic arbuscular
mycorrhiza in the soil. After germination,
the parasite’s radicle grows towards a
host, with haustorial growth induced
by host-derived phenolic compounds
or tactile cues. Holoparasites develop
terminal haustoria at the meristematic
tip of the primary root, which then
penetrates the host epidermis and
cortex, and attaches to the host
vasculature, followed by further plant
growth, fl owering, and senescence.
Facultative hemiparasites are much less
reliant on a host for completing their
lifecycle, with germination initiated by
seasonal cues but in the absence of a
host. Hemiparasites produce smaller
lateral haustoria at the transition zone
on the side of a growing root, which
attach to hosts and a range of nonspecifi c substrates (such as twigs).
What is exchanged between host
and parasite?
Hemiparasites are
predominantly xylem feeders and obtain
reduced carbon and nitrogen from
the host’s vasculature. Holoparasites
are predominantly phloem feeders
that typically also retain a xylem
connection, and obtain all mineral
nutrients, amino acids, soluble carbon
and water from the host
The plant which grows on another plant without apparent harm is called
an epiphyte. Epiphytes typically attach themselves to the surface of other plants, such as trees, for support. They derive moisture and nutrients from the air, rain, and debris that accumulates around them, rather than from the host plant. This relationship doesn’t harm the host plant, as epiphytes do not penetrate its tissues for sustenance.
examples of epiphytes
Orchids: Many orchid species are epiphytic and can be found growing on trees in tropical rainforests. They attach themselves to the bark or branches of trees and obtain nutrients from the air and rainwater.
Bromeliads: Bromeliads are another group of plants that often grow as epiphytes. They have rosettes of leaves that collect water, and their roots anchor them to trees or other surfaces.
Ferns: Some fern species are epiphytic and grow on trees or rocks. They often form a mat of roots that helps them absorb moisture and nutrients from the surrounding environment.
Spanish Moss (Tillandsia usneoides): Spanish moss is a well-known epiphytic plant found in the southeastern United States and other regions. It drapes over tree branches and absorbs water and nutrients from the air and rainfall.
Staghorn Fern (Platycerium spp.): Staghorn ferns are epiphytic ferns that attach themselves to trees or rocks. They have distinctive antler-like fronds that give them their name.
These are just a few examples of the many plants that have adapted to an epiphytic lifestyle. They can be found in a variety of habitats around the world, particularly in tropical and subtropical regions.
A saprophyte
also known as a saprotroph, is an organism that obtains its nutrients by decomposing dead and decaying organic matter. These organisms play a crucial role in ecosystems by breaking down dead plant and animal material, returning nutrients to the soil, and facilitating nutrient cycling.
Unlike parasites, which obtain nutrients from living organisms, saprophytes feed on non-living organic matter. They secrete enzymes that break down complex organic molecules into simpler forms that can be absorbed by the saprophyte for nourishment.
Common examples of saprophytes include certain types of fungi, such as mushrooms and molds, as well as some bacteria. They are essential for the decomposition of organic matter and the recycling of nutrients in natural ecosystems.
Translocation
Translocation is the process by which sugars, nutrients, and other organic compounds produced in the leaves during photosynthesis are transported to other parts of the plant, such as stems, roots, and fruits. This movement of substances primarily occurs through the plant’s vascular system, which consists of phloem tissue.
The main components involved in translocation are sugars and other organic molecules synthesized in the leaves. These substances are actively transported into the phloem sieve tubes, where they are transported to other parts of the plant as needed for growth, storage, or energy.
Translocation is a vital process for the distribution of nutrients and energy throughout the plant and is essential for plant growth, development, and reproduction.
Transpiration
Transpiration is the process by which water is absorbed by plant roots from the soil, moves upward through the plant, and is released into the atmosphere through small pores called stomata on the leaves. Transpiration primarily occurs through the process of evaporation from the surfaces of leaf cells.
Water uptake by plant roots creates a negative pressure gradient in the plant’s xylem vessels, causing water to move upward through the plant from roots to leaves. As water molecules evaporate from the surfaces of leaf cells into the surrounding air, they create a pulling force, known as cohesion-tension, that helps maintain the continuous flow of water from roots to leaves.
Transpiration serves several important functions in plants, including the transport of water and minerals from the soil, the regulation of temperature, and the maintenance of turgor pressure in plant cells.
In summary, translocation involves the movement of organic compounds within the plant, while transpiration involves the movement of water from the roots to the atmosphere. Both processes are essential for the survival and growth of plants.
Oxygen given off during the process of photosynthesis is derived from
water molecules (H2O).
During photosynthesis, plants absorb carbon dioxide (CO2) from the atmosphere through small openings called stomata on the surfaces of their leaves. This carbon dioxide is then converted into glucose (a type of sugar) through a series of biochemical reactions known as the Calvin cycle, which takes place in the chloroplasts of plant cells.
Meanwhile, light energy from the sun is absorbed by chlorophyll, a pigment found in chloroplasts. This light energy is used to split water molecules (H2O) into oxygen (O2), protons (H+), and electrons (e^-) in a process known as photolysis. The oxygen atoms released from the water molecules combine to form molecular oxygen (O2), which is released as a byproduct of photosynthesis.
In summary, the oxygen given off during photosynthesis comes from the splitting of water molecules, and it plays a crucial role in the atmosphere’s oxygen cycle and in sustaining aerobic life on Earth.
Xylem is a complex tissue in vascular plants that serves several crucial functions related to the transport of water, minerals, and providing structural support. Here are the main functions of xylem:
Water Transport: One of the primary functions of xylem is to transport water and dissolved minerals from the roots to the stems, leaves, and other parts of the plant. This process, known as transpiration, relies on the cohesion and adhesion properties of water molecules to create a continuous flow of water through the plant.
Mineral Transport: In addition to water, xylem also transports essential minerals and nutrients absorbed from the soil by the plant’s roots. These minerals, such as nitrogen, phosphorus, potassium, and others, are dissolved in the water and transported upward through the xylem to support various metabolic processes and plant growth.
Structural Support: Xylem provides structural support to the plant by forming a network of interconnected vessels and fibers that help maintain the plant’s overall shape and stability. The lignin-rich secondary cell walls of xylem cells provide rigidity and strength, enabling the plant to withstand mechanical stresses such as wind and gravity.
Storage: Xylem can also serve as a storage reservoir for water and nutrients during periods of excess uptake or availability. Some plants store water and carbohydrates in specialized xylem tissues, such as the parenchyma cells found in the wood of trees.
Defense Against Pathogens: Xylem can play a role in defending the plant against pathogens and pests by producing substances such as lignin and phenolic compounds that inhibit the growth of microbes and discourage herbivores from feeding on the plant tissues.
In summary, xylem is a multifunctional tissue that plays a vital role in water and mineral transport, structural support, storage, and defense mechanisms in vascular plants. Its efficient functioning is essential for the growth, development, and survival of plants in various environmental conditions.
Myopia:
Myopia, also known as nearsightedness, is a condition where individuals can see nearby objects clearly, but distant objects appear blurry. This occurs because light entering the eye focuses in front of the retina, rather than directly on it. As a result, distant objects are not properly focused onto the retina, leading to blurred vision.
Myopia often develops during childhood or adolescence and may worsen as the eye continues to grow. It is typically caused by the eyeball being too long, or the cornea being too steeply curved, which causes light to focus in front of the retina instead of on it.
Hyperopia:
Hyperopia, also known as farsightedness, is a condition where individuals can see distant objects clearly, but nearby objects appear blurry. In hyperopia, light entering the eye focuses behind the retina rather than directly on it. As a result, close-up objects are not properly focused onto the retina, leading to blurred vision.
Hyperopia can occur when the eyeball is too short, or the cornea is too flat, causing light to focus behind the retina instead of directly on it. It can also result from a combination of factors including the shape of the lens and the overall refractive power of the eye.
Differences between Myopia and Hyperopia:
Focusing Distance: The main difference between myopia and hyperopia is the distance at which objects appear blurry. In myopia, distant objects are blurry, while nearby objects are clear. In hyperopia, nearby objects are blurry, while distant objects are clear.
Eyeball Shape: Myopia is often associated with an elongated eyeball or a steeply curved cornea, which causes light to focus in front of the retina. Hyperopia is associated with a shorter eyeball or a flatter cornea, causing light to focus behind the retina.
Age of Onset: Myopia typically develops during childhood or adolescence and may worsen with age, while hyperopia may be present from birth or develop later in life.
Corrective Lenses: Both myopia and hyperopia can be corrected with eyeglasses, contact lenses, or refractive surgery. In myopia, concave lenses are used to shift the focal point onto the retina, while in hyperopia, convex lenses are used to do so.
In summary, myopia and hyperopia are both refractive errors of the eye that affect vision, but they differ in terms of the distance at which objects appear blurry and the underlying causes of the condition.
Paramecium is a unicellular organism belonging to the group of protists called ciliates. It possesses several specialized structures that enable it to carry out essential life functions. Here are the main parts of a Paramecium and their functions:
Cell Membrane: The cell membrane surrounds the entire cell and regulates the passage of materials into and out of the cell. It maintains cell integrity and helps Paramecium respond to changes in its environment.
Cilia: Paramecium is covered with numerous hair-like structures called cilia. Cilia beat in coordinated waves, allowing Paramecium to move through its aquatic habitat and also to sweep food particles into its oral groove.
Oral Groove: The oral groove is a specialized structure lined with cilia that leads to the mouth of the Paramecium. It functions in food capture and ingestion. The cilia lining the oral groove create currents that direct food particles towards the mouth.
Cytoplasm: The cytoplasm is the gel-like substance that fills the interior of the cell. It contains various organelles, enzymes, and other substances necessary for cellular processes such as metabolism, digestion, and protein synthesis.
Nucleus: Paramecium contains a single, large nucleus, which houses the organism’s genetic material (DNA). The nucleus controls cellular activities and coordinates cell functions such as growth, reproduction, and metabolism.
Contractile Vacuoles: Paramecium possesses contractile vacuoles, which are specialized structures involved in osmoregulation. Contractile vacuoles collect excess water that enters the cell by osmosis and expel it from the cell, helping to maintain the cell’s internal water balance.
Digestive Vacuoles: Digestive vacuoles are membrane-bound sacs that contain food particles ingested by the Paramecium. They fuse with lysosomes to digest food particles using enzymes, releasing nutrients that can be utilized by the cell.
Micronucleus and Macronucleus: Paramecium possesses two types of nuclei: micronucleus and macronucleus. The micronucleus is involved in genetic exchange during sexual reproduction, while the macronucleus controls gene expression and cell function during vegetative growth.
Contractile Fibers: Contractile fibers are protein structures found beneath the cell membrane. They help maintain the cell’s shape and aid in cell movement and contraction.
These are some of the main biology parts of Paramecium and their functions. Collectively, these structures enable Paramecium to carry out essential life processes such as locomotion, feeding, digestion, and reproduction.
Euglena is a single-celled organism classified as a protist. It exhibits characteristics of both plants and animals, which has led to some confusion regarding its classification.
Here’s why Euglena is sometimes classified as both plant-like and animal-like:
Plant-like Characteristics:
Euglena contains chloroplasts, which are responsible for photosynthesis, the process by which autotrophic organisms produce their own food using light energy.
During favorable conditions and in the presence of light, Euglena can carry out photosynthesis to produce sugars using carbon dioxide and water.
When Euglena photosynthesizes, it uses chlorophyll pigments to capture light energy, similar to plants.
Animal-like Characteristics:
Euglena is capable of movement using a whip-like structure called a flagellum. This flagellum allows Euglena to swim through water in search of nutrients or to escape unfavorable conditions.
Like animals, Euglena is capable of actively responding to its environment. It can detect changes in light intensity, temperature, and other environmental cues, and respond accordingly.
Because of its ability to perform photosynthesis like plants and its mobility and behavior like animals, Euglena is often classified as a mixotroph, meaning it can obtain energy through both autotrophic (photosynthetic) and heterotrophic (ingesting organic matter) means.
In taxonomy, Euglena is classified within the kingdom Protista, which includes a diverse group of eukaryotic organisms that do not fit neatly into the plant, animal, or fungi kingdoms. Within Protista, Euglena is further classified into the phylum Euglenozoa and the genus Euglena.
Mammals are a diverse group of animals that share several key characteristics. These characteristics distinguish them from other vertebrates. Here are some important characteristics of mammals:
Vertebrates: Mammals have a backbone or spine made up of vertebrae, which makes them part of the phylum Chordata.
Hair or Fur: Mammals have some degree of hair or fur on their bodies. This characteristic helps regulate body temperature and can serve various functions, such as protection and camouflage.
Mammary Glands: Female mammals possess mammary glands that produce milk to nourish their young. This is a defining feature of mammals, and the term “mammal” is derived from these mammary glands.
Warm-Blooded (Endothermic): Mammals are warm-blooded, meaning they can regulate their internal body temperature. This ability allows them to be active in a wide range of environments.
Live Birth or Viviparity: Most mammals give birth to live young, rather than laying eggs. However, there are exceptions, such as monotremes (platypus and echidna) that lay eggs.
Placenta (in Placental Mammals): Placental mammals have a placenta, an organ that provides nutrients and exchanges wastes between the mother and the developing offspring during pregnancy. This allows for a longer gestation period and more developed offspring at birth.
Specialized Teeth: Mammals typically have teeth of different types (incisors, canines, molars) that are specialized for different functions, such as cutting, tearing, and grinding food. The type of teeth reflects the animal’s diet.
Endoskeleton: Mammals have an internal skeleton, including a well-developed skull that houses and protects the brain.
Complex Brain: Mammals generally have a relatively large and complex brain compared to other vertebrates. This contributes to their ability to learn, adapt, and exhibit a wide range of behaviors.
Three Middle Ear Bones (Ossicles): Mammals have three small bones in the middle ear—ossicles (malleus, incus, and stapes)—which are involved in hearing and are unique to this group of animals.
Efficient Respiratory System: Mammals have a diaphragm, a muscular structure that aids in breathing by expanding and contracting the chest cavity.
These characteristics collectively define the class Mammalia, encompassing a diverse array of species ranging from small rodents to large whales and from aerial bats to terrestrial mammals like elephants and humans.
Hydrostatic Skeleton:
Hydrostatic skeletons are found in soft-bodied invertebrates, such as worms and some aquatic organisms. They rely on the pressure of fluid-filled compartments within their bodies to maintain their shape and provide support.
Exoskeleton:
Exoskeletons are external skeletons made of a tough, rigid material such as chitin. They provide protection and support for the insect’s body, as well as serving as attachment points for muscles. Common bugs with exoskeletons include insects like beetles, ants, and grasshoppers.
Endoskeleton
Endoskeletons are internal skeletons found within the bodies of vertebrates, including mammals, birds, reptiles, amphibians, and fish. These skeletons consist of bones or cartilage that provide support and protection for internal organs. They also serve as attachment points for muscles and aid in movement.
Cartilaginous Skeleton
Cartilaginous skeletons are composed primarily of cartilage, a flexible and relatively lightweight connective tissue. Cartilaginous skeletons are found in some fish, such as sharks and rays, as well as in certain amphibians and reptiles.
Bony Skeleton
Bony skeletons are composed of bones, which are rigid structures made of calcium phosphate and collagen fibers. Bony skeletons provide strong support and protection for the body, as well as serving as sites for muscle attachment and aiding in locomotion. Bony skeletons are found in most vertebrates, including mammals, birds, reptiles, amphibians, and fish.
A lenticel is a small, raised, corky or porous area found on the surface of stems, roots, and some fruits of woody plants. It serves several important functions:
Gas Exchange: Lenticels facilitate the exchange of gases between the internal tissues of the plant and the external environment. Oxygen and carbon dioxide can pass through the lenticels, allowing for respiration to occur in the plant’s tissues.
Transpiration: Lenticels also play a role in the release of water vapor from the plant through a process called transpiration. Although the primary route for transpiration is through the stomata on leaves, lenticels can also contribute to the loss of water vapor.
Aeration of Internal Tissues: In woody plants, lenticels provide a pathway for oxygen to reach the internal tissues, including the cambium layer where new cells are produced. Adequate oxygen supply is essential for cellular respiration and metabolic processes.
Protection: Lenticels may also help protect underlying tissues from damage by allowing gases and excess moisture to escape. In some cases, lenticels can become corky or develop a thickened protective layer to resist pathogens, insects, and other environmental stresses.
Overall, lenticels play a vital role in the physiology and health of woody plants by facilitating gas exchange, transpiration, aeration of internal tissues, and providing protection against environmental stressors.
Conjugation in Spirogyra is a method of sexual reproduction in which two filaments of Spirogyra algae come into close contact and exchange genetic material. Here’s a breakdown of the steps involved in conjugation:
become less favorable or during specific stages of the life cycle, sexual reproduction via conjugation may occur. Initially, two adjacent filaments of Spirogyra align side by side.
Development of Conjugation Tubes: Specialized cells called conjugation tubes form at the ends of the adjacent filaments. These tubes are composed of thin, tubular extensions of the cell walls of adjacent cells. The conjugation tubes grow and elongate towards each other, eventually connecting the two adjacent filaments.
Migration of Gametes: Within the filaments of Spirogyra, individual cells undergo specialized processes to produce gametes. These gametes are haploid reproductive cells containing half the number of chromosomes as the parent cell. In Spirogyra, the male gamete is called a sperm cell, while the female gamete is called an egg cell.
Fusion of Conjugation Tubes: Once the conjugation tubes from adjacent filaments meet and fuse, a continuous tube is formed between them. This tube allows for the exchange of genetic material between the two filaments.
Transfer of Genetic Material: The contents of the male gametes (sperm cells) from one filament are released into the conjugation tube and migrate towards the female gametes (egg cells) in the other filament. The sperm cells contain nuclei with genetic material that will be transferred to the egg cells.
Fertilization and Zygote Formation: When a sperm cell reaches an egg cell, fertilization occurs. The nucleus of the sperm cell fuses with the nucleus of the egg cell, resulting in the formation of a diploid zygote. The zygote contains a complete set of chromosomes from both the sperm cell and the egg cell.
Zygote Development: The zygote undergoes further development and differentiation, eventually forming a new filament of Spirogyra algae. The new filament grows and matures, eventually producing new cells through asexual reproduction, completing the life cycle of Spirogyra.
Overall, conjugation in Spirogyra involves the exchange of genetic material between adjacent filaments through specialized structures called conjugation tubes, leading to the formation of new individuals with genetic variation.
Properties of Plant Cells
Cell Wall: Plant cells have a rigid cell wall made of cellulose outside the cell membrane. The cell wall provides structural support and protection for the cell.
Chloroplasts: Plant cells contain chloroplasts, which are organelles that contain chlorophyll and are involved in photosynthesis, the process by which plants convert sunlight into chemical energy.
Large Central Vacuole: Plant cells typically have a large central vacuole that stores water, ions, and nutrients. The vacuole helps maintain turgor pressure, which provides structural support to the plant cell and helps regulate cell volume.
Plasmodesmata: Plant cells are interconnected by plasmodesmata, microscopic channels that allow for the exchange of water, nutrients, and signaling molecules between adjacent plant cells.
No Centrioles: Plant cells do not have centrioles, which are structures involved in cell division (mitosis and meiosis) in animal cells.
Properties of Animal Cells:
No Cell Wall: Animal cells do not have a cell wall like plant cells. Instead, they are surrounded by a flexible cell membrane that regulates the movement of substances into and out of the cell.
No Chloroplasts: Animal cells do not contain chloroplasts and cannot carry out photosynthesis. They obtain energy by breaking down organic molecules through cellular respiration.
Small Vacuoles: Animal cells may contain small vacuoles, but they are not as prominent or centrally located as the vacuole in plant cells. Vacuoles in animal cells primarily function to store water, ions, and waste products.
Centrioles: Animal cells contain pairs of centrioles, which are involved in organizing the microtubules of the cytoskeleton and are important for cell division.
Lysosomes: Animal cells contain lysosomes, membrane-bound organelles that contain digestive enzymes. Lysosomes break down waste materials, cellular debris, and foreign particles in the cell.
Overall, while plant and animal cells share many fundamental features, their specific structures and organelles reflect the unique functions and adaptations of plants and animals in their respective environments.
