As you walk through a forest, the plants and animals around you are obvious, but fungi are often overlooked. Yet fungi are integral to the health and functioning of ecosystems, and in many ways are more similar to animals than plants. You may be surprised by some of the characteristics fungi share with animals. Both animals and fungi are heterotrophs, meaning they absorb nutrients from their environment rather than producing their own food through photosynthesis. They also share similar cell structures, with cells that have nuclei and membrane-bound organelles. Some fungi can even move and hunt, displaying a level of mobility and behavior more commonly associated with animals. Despite their plant-like appearance, fungi are actually more closely related to animals. Read on to discover some of the fascinating ways fungi mirror their animal counterparts.
Cellular and Genetic Similarities Between Fungi and Animals
Fungi and animals share some surprising similarities at a cellular and genetic level.
Both fungi and animals are eukaryotes, meaning their cells contain a nucleus and membrane-bound organelles. They share similar cellular machinery for processes like protein synthesis, mitosis, and respiration.
- Fungi and animals both have lysosomes, mitochondria, a Golgi apparatus, and ribosomes.
- Their cells undergo mitosis, a process of cell division with distinct stages like prophase, metaphase, anaphase and telophase.
- They both use mRNA, tRNA and ribosomes to translate DNA into proteins.
Genetically, fungi and animals also share some similarities.
- Their genomes are organized into linear chromosomes.
- They both have histone proteins that help pack DNA into nucleosomes in the nucleus.
- Many of the same enzymes and pathways are found in fungi and animals, like the Krebs cycle for cellular respiration.
While fungi and animals belong to different kingdoms and diverged evolutionarily over a billion years ago, some of their fundamental cell biology has been conserved. These similarities point to a common ancestor that gave rise to the first eukaryotic cells. Though they went on to develop distinct characteristics, fungi and animals have retained a molecular kinship that underscores their shared evolutionary origins.
Despite their differences, at a basic level of cells and genes, animals and fungi are more alike than unalike. Their similarities run deep, all the way down to the microscopic machinery that powers life itself.
Growth and Development: Comparing Fungal Spores and Animal Embryos
Fungal spores and animal embryos share some surprising similarities in how they grow and develop.
Spores, the reproductive cells of fungi, are dispersed from the parent fungus and germinate into new fungal organisms under the right conditions. Likewise, animal embryos develop from fertilized eggs into larvae or juveniles and ultimately into mature individuals.
Germination and Implantation
Fungal spores must find a suitable environment to germinate, requiring factors such as moisture, nutrients, and temperature to be in the proper range. Similarly, embryos must implant in an environment with the right conditions to support growth, such as the uterus. For both spores and embryos, failure to find a proper environment results in death.
Cell Division and Differentiation
Once germinated or implanted, spores and embryos go through cycles of cell division and differentiation. Cells divide and multiply, then specialize into different cell types to form tissues and organs. This process transforms the single-celled spore or zygote into a multicellular organism.
With the right conditions, spores develop into mature fungal organisms such as mushrooms, while embryos develop into larvae, juveniles and eventually mature animals. At maturity, both fungi and animals can reproduce, starting the cycle over again.
Despite major differences, fungi and animals share some fundamental similarities in how they grow and propagate themselves through spores and embryos. A closer examination of these life cycles provides insight into the complex yet elegant processes that sustain all life on Earth.
Digestion: How Fungi and Animals Break Down Food
Fungi and animals have evolved different methods for extracting nutrients from their environment, but they share some striking similarities in how they break down and digest food.
Like animals, fungi take in food from their environment. Rather than eating, fungi absorb nutrients through their cell walls and membranes. Fungi secrete enzymes and acids onto food sources like decaying leaves and roots in the soil, breaking them down into smaller molecules that can then be absorbed. Animals, of course, ingest food through the mouth, breaking it down mechanically with teeth and chemically with saliva before swallowing.
Once food has been ingested, fungi and animals both rely on chemical digestion to break complex molecules into simpler compounds. Fungi use extracellular enzymes and acids to decompose nutrients into small molecules outside their cells that can then be transported inside. Similarly, animals use enzymes and stomach acids to digest food into small molecules within the gastrointestinal tract. Key steps in digestion, such as hydrolysis of proteins into amino acids, lipids into fatty acids, and carbohydrates into simple sugars, are common to both fungi and animals.
Absorption and Distribution
The end products of digestion, such as amino acids, fatty acids, and simple sugars, are absorbed by fungi and animals alike. In fungi, these small molecules diffuse directly through cell membranes into cells. Animals absorb nutrients through the lining of the gastrointestinal tract, transporting them into the bloodstream. Once absorbed, the nutrients are distributed throughout the fungi or animal to supply energy and building blocks for growth and maintenance.
While fungi and animals have evolved very different body forms, they share some similar strategies for extracting and distributing the nutrients they need to survive and thrive. The underlying biochemical processes that break down complex molecules into a useable form are fundamentally comparable across these groups.
Respiration: How Fungi and Animals Exchange Gasses
Respiration is the process by which organisms exchange gasses, absorbing oxygen and releasing carbon dioxide. Both fungi and animals carry out respiration to produce energy from food.
How Fungi Respire
Fungi respire through respiration. They take in oxygen and release carbon dioxide. However, unlike animals, fungi do not have specialized respiratory organs. Instead, fungi respire through their cell membranes. Oxygen diffuses into the fungal cells and carbon dioxide diffuses out.
The respiration of fungi occurs in two stages:
- Glycolysis – Glucose is broken down into pyruvate, producing a small amount of ATP and NADH. This occurs in the cytoplasm.
- Cellular respiration – Pyruvate is broken down further in the mitochondria through the Krebs cycle and electron transport chain. This produces most of the ATP from respiration.
Oxygen is required for the second stage of cellular respiration to occur. Without oxygen, fungi enter fermentation and produce ethanol and carbon dioxide as byproducts.
How Animals Respire
Like fungi, animals also respire through a two-stage process of glycolysis and cellular respiration to produce ATP from food. However, animals have specialized respiratory organs, such as lungs, gills or tracheal systems to take in oxygen and release carbon dioxide.
Oxygen diffuses into an animal’s respiratory surface, then binds to hemoglobin in red blood cells and is transported throughout the body. At the same time, carbon dioxide diffuses out of cells into the blood and is transported to the respiratory surface to be released.
The key difference in how fungi and animals respire is that animals have specialized respiratory organs and a circulatory system for transporting gasses, whereas fungi directly exchange gasses through their cell membranes. Despite these differences, respiration serves the same essential purpose in both fungi and animals – producing energy from food.
Response to the Environment: How Fungi and Animals Sense and Adapt
Fungi and animals have developed similar mechanisms for sensing and responding to their environment. Both have evolved complex systems for detecting light, chemicals, temperature, and physical contact.
Fungi detect light through photoreceptors in their cells that trigger physiological responses. Many fungi use light as a cue for developmental changes, such as the production of spores or fruiting bodies. Some fungi also exhibit phototropism, growing towards or away from light. Similarly, animals have evolved eyes and light-sensitive cells that detect light and allow for vision and circadian rhythms.
Chemical sensing allows fungi and animals to find food, mates, and habitats. Fungi use chemoreceptors to detect nutrients, toxins, and mating pheromones. Likewise, animals have an advanced sense of smell and taste enabled by chemoreceptors that can detect chemicals at low concentrations.
Thermoreceptors in fungi and animals detect temperature changes in the environment. Some fungi and animals are able to migrate or hibernate in response to temperature shifts. Others have adaptations that allow them to remain active in extreme temperatures.
Physical contact sensing refers to mechanoreception. Fungi can detect physical disturbances, pressures, and surface contact through mechanoreceptors. These allow fungi to anchor themselves to surfaces, detect damage, and potentially avoid predators. Similarly, animals have touch receptors, proprioceptors, and balance receptors (mechanoreceptors) that provide information about the physical environment and body position.
In summary, fungi and animals share similar abilities to sense and respond to critical environmental factors like light, chemicals, temperature, and physical contact. These advanced sensory and regulatory systems have evolved in both groups as adaptations for growth, reproduction, and survival.
As you’ve discovered, fungi and animals share some unexpected similarities despite being separated by over a billion years of evolution. Both kingdoms demonstrate the power of natural selection to converge on common solutions to biological problems. At their core, all organisms have the same basic needs – to acquire nutrients, grow, and reproduce. The remarkable ways fungi and animals have adapted to fulfill these needs serve as a reminder of the interconnectedness of life on Earth. Though fungi and animals took vastly different evolutionary paths, their shared biological imperatives led to the development of analogous structures and behaviors. Nature’s experiments often yield similar results.