Explore the vast range of titles available.

Exponential model for population growth (exponential model) is a foundation to evaluate population dynamics in Population Ecology field. Here, we used a didactic experiment to teach exponential model for an undergraduate course of Population Ecology. We built nine populations of weevils with three different initial population sizes: eight, 16, and 32 individuals with three replicates each. We provided equal food resource availability, and counted their population sizes weekly for 12 weeks. We estimated the intrinsic growth rate (i.e., r parameter), by trials and errors with an exponential model build in an Excel spreadsheet. The population growth rate (i.e., dN/dt parameter) was estimated using r values. Replicates with eight and 16 individuals reached the highest values of r and dN/dt, while replicates with 32 individuals reached the lowest values. Beyond of exponential model, two density dependency issues acting in populations were observed. First, in the lowest initial population sizes we observed the effect of demographic stochasticity acting in both r and dN/dt in one of the three populations. Second, we observed the intraspecific competition reducing r values in largest initial populations. Therefore, we highlight the importance of didactic experiment into learning exponential model in Population Ecology course, both for teaching and learning practices.    

A agricultura familiar tem papel importante na produção e distribuição de alimentos no Brasil, o que contribui significamente para economia e redução do êxodo rural. Porém enfrentam importantes desafios na comercialização dos seus produtos, como a competição desleal em relação à agricultura convencional, no entanto, ao logo dos anos vem ganhando nichos de mercados específicos. É nesse cenário que se insere este trabalho cujo objetivo central foi analisar os canais de comercialização utilizados pelos agricultores familiares nas comunidades de Guaíba, Terra Vermelha e Tupim, no município de Cachoeira-BA, e, especificamente, compreender os impactos da COVID-19 na comercialização. Metodologicamente foi realizada uma pesquisa de campo, somada ao levantamento bibliográfico. Em campo foram realizadas entrevistas semiestruturadas com os agricultores/as familiares das três comunidades. Os resultados indicaram que as comunidades utilizam três principais canais de comercialização: circuitos curtos, mercados institucionais e atravessadores. No entanto, os agricultores enfrentam desafios significativos, especialmente em relação à logística, à depreciação dos produtos e à burocracia nos mercados institucionais. Durante a pandemia, embora a produção agrícola não tenha sido severamente afetada, a comercialização sofreu impactos diretos. Os circuitos curtos enfrentaram os maiores desafios durante o lockdown, resultando em prejuízos econômicos, especialmente entre aqueles que dependiam das feiras livres para escoar seus produtos. Além disso, os mercados institucionais alteraram sua dinâmica, demandando produtos menos perecíveis e com menor frequência. Este trabalho concliu que, apesar das adversidades exacerbadas pela pandemia, a agricultura familiar demonstrou resiliência. Os agricultores continuam a desenvolver estratégias para enfrentar as dificuldades, fortalecendo seus laços comunitários e adaptando-se às novas condições impostas pelo mercado, sobretudo, frente ao distanciamento social. A pesquisa destacou a importância da agricultura familiar como um pilar fundamental na segurança alimentar e na economia local, mesmo em tempos de crise.

Family farming plays an important role in food production and distribution in Brazil, contributing significantly to the economy and reducing rural exodus. However, they face significant challenges in marketing their products, such as unfair competition from conventional agriculture. However, over the years, they have been gaining specific market niches. This study, whose main objective was to analyze the marketing channels used by family farmers in the communities of Guaiba, Terra Vermelha, and Tupim, in the municipality of Cachoeira, Bahia, and, specifically, to understand the impacts of COVID-19 on marketing. Methodologically, field research was conducted in conjunction with a literature review. Semistructured field interviews were conducted with family farmers from the three communities. The results indicated that the communities use three main marketing channels: short supply chains, institutional markets, and intermediaries. However, farmers face significant challenges, especially regarding logistics, product depreciation, and bureaucracy in institutional markets. During the pandemic, although agricultural production was not severely affected, marketing was directly impacted. Short supply chains faced the greatest challenges during the lockdown, resulting in economic losses, especially among those who relied on street markets to sell their products. Furthermore, institutional markets changed their dynamics, demanding less perishable products and less frequently. This study concluded that, despite the adversities exacerbated by the pandemic, family farming demonstrated resilience. Farmers continue to develop strategies to cope with difficulties, strengthening their community ties and adapting to the new market conditions, especially in the face of social distancing. The research highlighted the importance of family farming as a fundamental pillar of food security and the local economy, even in times of crisis.