IB MYP 4-5 Biology-Unity & Diversity in Life Forms- Study Notes - New Syllabus
IB MYP 4-5 Biology-Unity & Diversity in Life Forms- Study Notes – New syllabus
IB MYP 4-5 Biology-Unity & Diversity in Life Forms- Study Notes – IB MYP 4-5 Biology – per latest IB MYP Biology Syllabus.
Key Concepts:
- Shared characteristics of life (MRS GREN)
- Biodiversity hotspots
- Convergent vs. divergent evolution
Unity and Diversity in Life Forms
Shared Characteristics of Life – MRS GREN
Introduction:
Despite the incredible diversity of living organisms from bacteria to blue whales all life forms share a common set of features. These features define what it means to be “alive.” A helpful way to remember them is through the acronym MRS GREN.
MRS GREN: The 7 Characteristics of Life
Each letter in MRS GREN stands for a fundamental process that all living organisms perform:
M – Movement: All living things can move in some way. Animals move their whole bodies, plants move parts of their structure (e.g., turning toward light), and even single-celled organisms like amoeba move using structures like pseudopodia or flagella.
R – Respiration: The process of releasing energy from food. Most organisms use oxygen (aerobic), while some can respire without it (anaerobic).
S – Sensitivity (Response to Stimuli): Organisms can detect and respond to changes in their environment. For example, plants grow toward light, and animals respond tosound, touch, and temperature.
G – Growth: All living things grow by increasing the number or size of their cells. Growth may be gradual or rapid, depending on the organism.
R – Reproduction: Organisms reproduce to pass on genetic material. This can be asexual (one parent, identical offspring) or sexual (two parents, with variation).
E – Excretion: The removal of metabolic waste products. In humans, urea is excreted in urine, and plants release oxygen and gases through stomata.
N – Nutrition: The intake and use of nutrients. Animals consume food, while plants synthesize it through photosynthesis.
Summary:
Although life comes in many forms, all living things from the simplest microbes to the most complex animals share the same basic life processes. These processes keep organisms functioning and are the unifying features of biology. MRS GREN offers a simple but powerful tool to understand the unity behind life’s diversity.
Biodiversity Hotspots
What Is Biodiversity?
Biodiversity refers to the variety of life found on Earth ranging from genes and species to entire ecosystems. It is essential for sustaining ecosystems, supporting food chains, and maintaining climate balance.
What Is a Biodiversity Hotspot?
A biodiversity hotspot is a region with an exceptionally high number of species, many of which are endemic (found nowhere else), and that is also under significant threat from human activities.
The concept was introduced by ecologist Norman Myers in 1988 to help guide global conservation efforts.
Criteria for Biodiversity Hotspots
- Must have at least 1,500 species of vascular plants as endemics.
- Must have lost at least 70% of its original natural vegetation.
Only regions that are both rich in biodiversity and under significant threat qualify as hotspots.
Global Biodiversity Hotspots
Currently, 36 regions are recognized as biodiversity hotspots. Though they cover just 2.3% of the Earth’s land surface, they contain over 50% of the world’s endemic plant species.
Examples include:
- Amazon Rainforest (South America)
- Himalayas (Asia)
- Indo-Burma Region (South and Southeast Asia)
- Sunda land (Indonesia, Malaysia)
- Madagascar and Indian Ocean Islands
- Western Ghats and Sri Lanka (India)
- California Floristic Province (USA)
- Horn of Africa
Biodiversity Hotspots in India
- The Himalayas: Includes northeast India and parts of West Bengal
- Indo-Burma Region: Covers northeastern states and Andaman Islands
- Western Ghats and Sri Lanka: A chain of hills along India’s western coast
- Sunda land: Includes Nicobar Islands and parts of Southeast Asia
These regions house numerous endemic plants, mammals, amphibians, and insects, making India one of the most biodiverse nations globally.
Threats to Biodiversity Hotspots
- Deforestation and habitat loss
- Climate change
- Poaching and illegal wildlife trade
- Invasive species
- Agricultural expansion and urbanization
Importance of Protecting Hotspots
- Preserve unique species from extinction
- Maintain ecological balance
- Ensure genetic diversity
- Support local and global climate stability
- Provide vital ecosystem services like pollination, clean air, and water
Biodiversity hotspots represent Earth’s most valuable yet vulnerable ecological treasures. Protecting them is essential to preserving species, ecosystems, and the environmental balance needed for future generations.
Convergent vs. Divergent Evolution
What Is Evolution?
Evolution is the process by which populations of organisms change over generations. It can result in the formation of new species and is driven by natural selection, mutations, genetic drift, and environmental pressures.
Convergent Evolution
Definition: Convergent evolution occurs when unrelated species evolve similar traits independently due to similar environmental challenges, not shared ancestry.
Key Point: Different origins, similar outcomes.
- Example 1: Wings of birds (reptilian ancestors) and bats (mammalian ancestors) – functionally similar for flight, but structurally different.
- Example 2: Sharks (fish) and dolphins (mammals) – both have streamlined bodies for aquatic life.
Result: Analogous structures – same function, different origin.
Divergent Evolution
Definition: Divergent evolution is when related species evolve different traits due to adaptation to different environments.
Key Point: Same ancestry, different adaptations.
- Example 1: Darwin’s finches – all evolved from a common ancestor but developed different beak shapes for different food sources.
- Example 2: Forelimbs of vertebrates (humans, cats, whales, bats) – same basic bone structure, adapted for different functions.
Result: Homologous structures – same origin, different function.
Comparison Table
| Feature | Convergent Evolution | Divergent Evolution |
|---|---|---|
| Ancestry | Different ancestors | Common ancestor |
| Structures | Analogous | Homologous |
| Environmental Pressure | Similar | Different |
| Examples | Birds and bats, sharks and dolphins | Darwin’s finches, vertebrate forelimbs |
| Outcome | Similar features evolve independently | Differences arise from shared origin |
Summary:
Convergent evolution illustrates how unrelated organisms can develop similar adaptations. Divergent evolution explains how related organisms can grow apart over time. Both are essential in understanding the patterns and outcomes of evolutionary change.