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Terrestrial Biomes Overview
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0:01
[Music]
0:17
Hello, I am Dr. William Schlosser, Washington State University, School of the Environment, and this is my classroom!
0:26
[Music]
0:35
As we look into terrestrial biomes, we arrange landscapes by the types of vegetation we can recognize. There are eight major terrestrial biomes: tropical rainforests, savannas, tropical deserts, chaparral, temperate grasslands, temperate forests, boreal forests, and arctic tundra. Biomes are large-scale environments that are distinguished by characteristic temperature ranges and amounts of precipitation accompanied by energy delivery timing.
1:07
These variables affect the types of vegetation and animal life that can exist in those areas. Because each biome is defined by climate, the same biome can occur in geographically distinct areas with similar climates. However, similar vegetative habitats do not necessarily produce identical animal life. Divergent animal genetics reveal how adaptations are acquired as solutions to similar challenges. Those are the challenges of life.
1:38
We have talked about the biome concept through this study of ecology, to understand how it is formed in response to geology, climate, topography, sunlight energy and an intermix of biodiversity opportunities. This includes the effects of time on how energy is acquired and processed in each phase of plant lives. In ecology, we recognize how nothing remains static from one generation to the next. Even climatic changes are not conveyed in a static way.
2:10
We measure this progression using the metric of time. We look across north America to see many adjacent areas possessing similar biomes. We looked at the specific example of the Pacific Coastal Evergreen Forest, and the disjunct biome by the same name resting 500 miles inland in Idaho and British Columbia. Diversity does not stop there. Consider the steppe vegetation spanning lands from Alberta, Canada, through the United State and reaching into Gulf of Mexico shorelines in northeastern Mexico.
2:44
Is that biome uniform across this reach? Of course there is variation within this biome! We look to the plants that occupy these lands to give us a firm understanding of how energy is acquired and transformed into semi-stable expressions. Plants do not migrate to new habitats between seasons like many animals do. At the same time, antelope living in the steppe vegetation of Montana are not found in the western interior shrub steppe and woodland areas of Washington.
3:14
They look similar enough, right? Why do we not see those goats near Othello, Washington? There must be something more to this equation. Hmm. TALK about that one as you consider how biomes are shown as reflecting precipitation and temperature with FUZZY LINES separating them. They are never hard drawn transitional positions. While it works to understand some plants, it is different when we consider the mobile animals calling this habitat home.
3:45
Terrestrial biomes are characterized by dominant plant growth forms that are best adapted to the environmental conditions of climatic regions. Adaptations are acquired by plants from one generation to the next. Genetic mutations happen in every species, in almost every offspring at conception. I was once told by a geneticist colleague that we can look at the human genome and find that about four mutations are present in each human child. Some of these are completely unnoticed, some are obvious.
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I have a family member who was born with 11 fingers. The spare was clipped at birth, so she grew without that mutation showing. Physically unnoticed, but it resides in her genome. Some mutations create a benefit for the offspring. It may be physical speed, mental cognition, memory, or analytical prowess. Height, build, or physical stature may be favored within the genetic selection criteria. It is only when selective pressures favor these mutations that they can potentially
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be spread within a species. These mutations are entered into the broad genome only when they are successfully passed to offspring. This gives rise to the axiom about natural selection where you might have heard about the survival of the fittest. Reword that to understand how evolution is about the survival of the genetically reproductive traits passed to offspring. It all comes to heritability through differential reproductive success. These mutations create variability within each population.
5:23
The collection of these adaptations, as they are passed through generations, can lead to speciation.
5:33
Plants are fixed to the places where they germinated, right? Only in the movies like Lord of the Rings can trees get up and walk around. In our world, plants adapt through generations in the form of genetic migrations to remain in sync with features of presented by their environments. Where different animal and plant species respond to the same characteristic biome types, the characteristics they develop will typically result in similar adaptations.
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However, that does not mean they are genetically identical. Species interact and breed to share their adaptations. That is, until there is a spatial or temporal break in their intermixing unions. An organism's genotype is the set of genes that it carries. An organism's phenotype is all of its observable characteristics, which are influenced both by its genotype and by the environment. In the world of nature, these mutations give adaptation opportunities.
6:34
We will explore that one soon, but for now consider the broad range of variability in the biotic and abiotic combinations we witness around the world. Morphology is the branch of biology that deals with the form of living organisms, and with relationships between their structures. Morphology is a branch of biology dealing with the study of the form and structure of organisms and their specific structural features. A woody plant produces wood as its structural tissue.
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Woody plants are usually either trees, shrubs, or lianas. These are usually perennial plants whose stems and larger roots are reinforced with wood produced from secondary xylem. A herbaceous plant is a plant that does not have much wood and its stems are green and soft. These plants grow fast and produce flowers and many seeds in a short period of time. These are how plants have adapted to ever-changing biotic conditions.
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Keep this progression moving forward to recognize how plants exist together in the same biome. Each occupying a different niche within the biome. Herbaceous plants are non-woody plants, such as most ferns and grasses, which either form tiny amounts of hard woody tissue, or none at all. Unlike woody plants, such as trees, these plants don't have a stem that will remain above the ground when their leaves die. A fern is a member of a group of vascular plants, that is plants with both xylem and
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phloem, and reproduce via spores having neither seeds nor flowers. Ferns first appeared in the fossil record about 360 million years ago in the middle Devonian period. These evolutionary progressions have been unfolding alongside their peers in each biome.
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Non-vascular plants are plants without a vascular system consisting of xylem and phloem. Although non-vascular plants lack these particular tissues, many possess simpler tissues that are specialized for internal transport of water. Non-vascular plants do not have a wide variety of specialized tissue types. Mosses and leafy liverworts have structures called phyllids that look like leaves, but are not true leaves at all because they are single sheets of cells with no internal air
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spaces, no cuticle or stomata and no xylem or phloem. Consequently, phyllids are unable to control the rate of water loss from their tissues and are said to be poikilohydric. A lichen is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationships. Lichens have different properties from those of its component organisms. Lichens come in many colors, sizes, and forms and are sometimes plant-like,
9:38
but lichens are not plants.
9:44
Ecological hierarchy theory describes the arrangement of biological organisms in relation to one another. At the individual level, interactions with other organisms are not considered. We consider them one at a time. Their assembly into working biospheres is revealed as biomes. The hierarchical level of an ecosystem is the different levels at which species or organisms of the ecosystem live. In short, it involves the entire biosphere.
10:14
Interactions among organisms within or between overlapping niches can be characterized into five types of relationships: competition, predation, commensalism, mutualism and parasitism. Symbiosis refers to a close relationship in which one or both organisms obtain a benefit. In evolutionary biology, convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological pressures.
10:52
It reveals how different species evolve within similar biomes, facing analogous challenges as their colleagues. They independently develop genetic adaptations to survive and thrive. In these cases, success is measured at the fundamental level of living and effectively reproducing with a mate sharing a similar mutation. As rare as that sounds, it can be seen when the favorable mutation holds a dominant gene, matched with a recessive gene in its mate.
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When successfully transferred and it benefits the survival and success of the offspring, the trait begins a lineage chain. Success is measured to the reproductively most successful trait.
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Convergent evolution is the independent evolution of similar features in species of different lineages. They are not sharing genes. Convergent evolution creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups. The cladistic term for the same phenomenon is homoplasy.
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Amino acid replacement is a change from one amino acid to a different amino acid in a protein due to point mutation in the corresponding DNA sequence. It is caused by nonsynonymous missense mutation which changes the codon sequence to another code amino acid instead of the original. Divergent evolution or divergent selection is the accumulation of differences between closely related populations within a species, leading to speciation.
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Divergent evolution is typically exhibited when two populations become separated by a geographic barrier, such as in allopatric or peripatric speciation, and experience different selective pressures that drive adaptations to their new environment. Parallel evolution is the similar development of a trait in distinct species that are not closely related, but share a similar original trait in response to similar evolutionary pressures.
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Given a particular trait that occurs in each of two lineages descended from a specified ancestor, it is possible in theory to define parallel and convergent evolutionary trends strictly, and distinguish them clearly from one another. However the criteria for defining convergent as opposed to parallel evolution often are unclear in practice, so that arbitrary diagnosis is common in some cases.
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Most cacti have spines or scales, which are modified leaves. These spines and scales do not lose water through evaporation, unlike regular leaves, which lose a lot of water through their stomata. The cacti spines protect the cactus from predators, those animals that would like to eat the cactus to obtain food and water. Areoles are circular clusters of spines on a cactus. Flowers bud at an areole and new stems branch from here.
13:59
Looking at these species which developed from different linages in the same environment, they formed several characteristics that are successful in this unique environment. This is Evolutionary Convergence. Not closely related, some come from different continents and have only distantly related genomes, well at least they are all mammals! Striped mice, which live in an arid habitat with large seasonal variation in food abundance, are well adapted to their environmental conditions.
14:31
Genetically they have adapted to survive and thrive. The spinifex hopping mouse, also known by its traditional Aboriginal name tarkawara, thrives in the red-hot arid zone of Australia, where they play an important role in maintaining the ecological balance. This mouse’s most unique feature is the way they’ve evolved to conserve water so that they can continue thriving in Australia’s harsh desert climate. This hopping mouse is said to have the most efficient, albeit tiny kidneys, which allow
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them to produce the most concentrated urine of any mammal ever recorded. They get most of their water from the things they eat, so they’re really good at processing the water out of their food. Their kidneys continue to recycle and re-absorb water from the food they eat. They end up with a urine that’s pretty much solid, consisting of only the waste material that they excrete from their body. Where form and function led these mice to convergent evolution solutions, their individual
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genomes developed unique mutations to guarantee their population’s success.
15:42
Before anthropogenic landscapes took hold on in the North America Western Interior Temperate Shrublands & Woodlands Biome, a balance was reached. Consider the species seen here. We are close to Pullman, at Kramer Prairie. We see environments where plant communities evolved. These plants, being from common and different ancestries developed adaptations to the climate regimes where they interact. Common or unique adaptations lead to success or failure.
16:12
Mostly, we witness only the successes, but recognizing the commonality between diverse species leads to understanding. Anthropogenic landscapes are areas of Earth's terrestrial surface where direct human alteration of ecological patterns and processes is profound, ongoing, and directed toward servicing the needs of human populations for food, fuel, fiber, timber, shelter, trade and recreation. This is where natural selection admits anthropogenic influences.
16:47
We change the participant profile in the array of sustained genetic materials. It may come from our selection pressures, removal of undesirable species, introduction of off-site species, or delivery of irrigation waters to change the historic adaptation patterns. It is tangible, it is meaningful, and we are influencing successes.
17:12
How many forms of anthropogenic landscapes can you identify here? We keep coming back to Kamiak Butte and looking southward from the crest of the butte to see agriculture, cities, and human rural developments. Whether native vegetation or anthropogenically influenced ecosystems, we need to consider interactions, climate, soils, topography, disturbance, and time. We have talked about this list before in different frameworks, so keep these considerations alive in your analytical thoughts.
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The introduction of time guarantees change will happen. Consider the reactive nature of the native vegetation to cattle grazing, weed herbicides, agricultural fertilizers, and the change to the native wildlife that originally occupied these sites. There is an impact, some “favorable” and some “undesirable”. Those are value statements applied by the humans who affected them. Fundamentally, they are changes to the natural balance and we must accept that interaction.
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Remember, we are part of the environment too.
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You are looking to describe an area, to convey a snap-shot in time allowing a reader to truly understand what you are looking at. The biome is one fundamental podium to pause at. Begin by describing what we are looking at, where it is located, and how it is described. Only with those data can we make meaningful comparisons between sites, separated by miles, across mountain ranges, or spanning continents. Biomes have a name, but you will need to cite the source of your description so all readers
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can share your understanding. Your efforts will be assisted by including a photographic representation of a plant community in the biome you portray, tell where it is located, its elevation, and the physical site attributes you know. Start with the biome’s physical location. Big picture data. Step into its defining taxa. Explain what types of vegetation exemplify these areas. Now you can reach into the macroclimate of the area you define. Illustrate its moisture profile in broad terms.
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This is not the time to define its annual precipitation. That comes in the definition of its climate. Finally, your biome description will outline the major disturbance regimes like fire, logging, settlement, insect outbreaks, and anthropogenic influences.
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While you are doing this, be careful not to confuse a biome with a macroclimate, a mesoclimate, or a microclimate. Those definitions are not how biomes are conveyed. The biome will have many mesoclimates, and countless microclimates within it. On this scene, you see many ecosystems within this Western Interior Evergreen Forest biome. It is located along the eastern edge of the Cascade mountains and when you define this
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biome alongside its climate and topography, your readers will capture the essence of this ecological unit. This is your podium to launch from.
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We describe environments where plants and animals interact. Our descriptions lay the foundation of how energy is acquired by plants and ultimately transferred to animals living in this space. We attempt to describe abiotic assemblies that create conditions of flourishing ecosystems. You will often see me looking up within these habitats. This is done to appreciate how photosynthesizing plants capture that original sunlight energy. It all starts there, but that is not the endgame.
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Forces of biotic and abiotic initiation interact and modify. That is the nature of these normal processes. Our anthropogenic influences may impact how these reveal, but ultimately we are part of this environment, alongside all other biotic participants.
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